J4500 Basic March 2003 Maintenance Manual

Unit-Index.1

VEHICLE UNIT INDEX

March 2003

December 2022 Vehicle Unit Index

 MCI
Maintenance
Manual
03-15-3809
J4500
March 2003 Edition
 Date March 2003

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . INT
Front Axle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Rear Axle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Body . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Brakes & Air System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Clutch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Cooling System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Electrical System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Fuel System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Lubrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Steering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Suspension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Driveshaft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Wheels, Hubs & Tires . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Heating & Air Conditioning . . . . . . . . . . . . . . . . . . . . . . 16
Lavatory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Wheelchair Lift Supplement . . . . . . . . . . . . . Appendix A
Specials Supplement . . . . . . . . . . . . . . . . . . . Appendix B
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IDX
MOTOR COACH INDUSTRIES
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 Date March 2003 Page Intro-1

INTRODUCTION
MAINTENANCE MANUAL
This manual contains maintenance information on the MCI J4500 coach. Information pertains to standard
equipment and commonly used optional equipment. Vehicle operation is covered in the Operator’s Manual. Detroit
Diesel engine and Allison transmission information is available in vendor service manuals.
All information in this manual is based on the latest information available at the time of publication. We reserve the
right to alter the publication at any time. Some illustrations in this manual were provided courtesy of the vendors. Typical
illustrations may be used, and differences may exist between the illustrations and actual parts or other publications.

HOW TO USE THIS MANUAL

This manual is divided into major sections in the sequence shown in the Section Index. Major sections are divided
into subsections, with the subsection breakdown given on the section’s title page. Each subsection begins with a table
of contents that lists the page numbers of topics such as operation, maintenance, lubrication, replacement and
troubleshooting.
Where applicable, component data and tolerances, specialized tools and torque specifications are given at the end
of the subsection. If part numbers are given, they are for reference only and should be verified through the latest
revision of the Parts Manual.
An alphabetical index is provided at the back of the manual.
Revisions
This manual may be revised to update existing information. Changes will be indicated with revision bars (bold,
vertical lines to the left of the text). Revision bars flag content changes made since the previous printing.
Service Bulletins
Service Bulletins are issued, when required, to supplement or supersede information in this manual. Information in
the bulletins must be noted and filed for future use.

CUSTOMER SERVICE
Motor Coach Industries is committed to your complete satisfaction. MCI service departments in the U.S. and
Canada offer genuine factory parts for this coach.

S MCI Customer Support Center, 422 West Stutsman Street, P.O. Box 528, Pembina, North Dakota 58271-0528
Phone: 1-800-241-2947; Fax: 701-825-6956

S MCI Service Department, 1475 Clarence Avenue, Winnipeg, Manitoba R3T 1T5
Phone: 1-800-241-2947; Fax: 204-474-1554

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MAINTENANCE
Proper maintenance is important to the safe and reliable operation of all vehicles. The service procedures
recommended and described in this manual are effective methods for performing service operations. In some
instances, the use of special tools is recommended. These tools should be used when and as recommended.
Service intervals are given as recommended minimum guidelines. These intervals, however, may not be appropriate
for all applications. Service intervals must be determined by the coach owner and experienced shop personnel based
on operating conditions, component history and previous experience.

WARNINGS, CAUTIONS AND NOTES

This manual contains various WARNINGS, CAUTIONS and NOTES. Read these carefully to minimize the risk of
personal injury or improper service. These notices are not all inclusive. We could not evaluate and advise users of all
conceivable ways in which service could be done or of the possible hazardous consequences of each approach.
Anyone who uses a service procedure or tool should first verify that neither personal safety nor vehicle safety will be
jeopardized.

WELDING CAUTION1
The following information must be read and understood before beginning any welding. The prohibitions and
requirements must be followed.

IMPORTANT: This coach is equipped with electronic controls. Do not weld until the following steps have been
completed. Do not disconnect battery ground cable.

1. Welding must only be done by an experienced and qualified person. All welding must conform to AWS’s D1.1
Structural Welding Code. All applicable instructions and prohibitions must be followed.
2. Adequate ground contacts and barriers must be positioned as close as possible to the weld area and as required
to protect components (wiring, brake lines, hydraulic lines, etc.) from damage due to heat, contact by weld
splatter or arcing.
3. Switch the main battery disconnect OFF.
4. Disconnect the following:
Battery Compartment
a. Unplug battery charger from A/C supply.
b. All connectors from WTEC ECU.
c. All connectors from HVAC controller.
d. All connectors from ground module.
e. 24 volt cable at battery.
Engine Compartment
f. P-36 and P-50 (engine adapter harness).
RH Baggage Compartment
g. Four (4) large bulkhead connectors.
Front Junction Box
h. All dash connectors.
i. Two (2) connectors on relay modules.
5. After welding, reconnect items in reverse order. Warn people in the immediate area before turning the main battery
disconnect ON.

DRILLING CAUTION
Due to the close proximity of electrical and mechanical lines to the aisle floorboard, do not drill holes in the center
tunnel area. This area is 15 inches wide and runs immediately under the coach center aisle for the full length of the
coach.
Do not drill in the back side of the right-hand and left-hand B-post or the A-post from the mirrors down.

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Figure 1. J4500 Model Body and Door Clearance Diagram

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46’--6”
14.17m

Figure 2. Turning Radius and Door Clearance

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GENERAL DATA

VEHICLE LENGTH: Over Bumpers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45.58 ft. (13.89 m)

VEHICLE HEIGHT: Top of Roof Hatch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141.25” (3.59 m)
VEHICLE WIDTH: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102” (2.59 m)
TURNING RADIUS (Front Body with Bumper): . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46.5 ft. (14.17 m)
WHEELBASE: Front Axle to Drive Axle Centers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315” (8.0 m)
FRONT AXLE TRACK: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84.84” (2.15 m)
REAR AXLE TRACK: (Center of Dual Wheels) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75.38” (1.91 m)
TAG AXLE TRACK: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84.84” (2.15 m)
GROSS VEHICLE WEIGHT RATING: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54,000 lbs. (24,494 kg)
APPROXIMATE PAYLOAD CAPACITY: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12,900 lbs. (6531 kg)
FUEL CAPACITY: (Standard Tank) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183 Gal. U.S. (693 liters)
COOLING SYSTEM CAPACITY: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Gal. U.S. (100 liters)
STEERING SYSTEM CAPACITY: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5 Qts. U.S. (7.1 liters)
TIRE RATING: (Minimum) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . “J” Rated

ENGINE DATA
Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Detroit Diesel Series 60
Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Cycle
No. of Cylinders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Bore . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.12” (130 mm)
Stroke . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3” (160 mm)
Compression Ration (Turbo) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15:1
Total Displacement (Cubic Inches) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 775 cubic inches (12.7 liters)
Number of Main Bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

MANUFACTURER CONTACT NUMBERS

Allison (transmissions) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-800-524-2303 (24 hour)
Detroit Diesel (engine) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-800-445-1980
Carrier (heating and air conditioning) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-800-450-2211 (8AM - 6PM EST)
Wabco (ABS brakes) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-800-535-5560

MOTOR COACH INDUSTRIES

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 Date March 2003

SECTION 1
FRONT AXLE

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SECTION 1

FRONT AND TAG AXLES

CONTENTS OF THIS SECTION
SUBJECT PAGE

General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3

Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
Routine Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
Steering Knuckle End Play . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
King Pin Bushings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
Tie Rod . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6
Lubrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-7
King Pins, Tie Rod Assemblies and Ball Studs . . . . . . . . . . . . . . . . . . . 1-7
Daily Wheel Bearing Oil Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-7
Wheel Bearing Oil Change . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-7
Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-8
Tie Rod, Tie Rod Arm, Tie Rod Ends . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-8
Knuckle Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-8
Cleaning and Parts Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-11
Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-11
Corrosion Prevention on Cleaned Parts . . . . . . . . . . . . . . . . . . . . . . . . . 1-11
Parts Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-11
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-14
Steering Knuckle Bushing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-14
Reaming Knuckle Bushings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-14
Inner Knuckle Bushing Seals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-15
Knuckle Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-16
Tie Rod Arm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-19
Tie Rod and Tie Rod Ends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-19
Adjustments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-20
Wheel Bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-20
Steering Stop Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-21
Pressure Relief Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-21
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-22
Torque Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-23
Service Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-24
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-25

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Tie Rod

Tie Rod Arm

Threaded King Pin Cap

Grease Fitting
Steering Arm

Shims

Bushing

Axle
Tie Rod Arm

Bearing

Steering Knuckle

King Pin

Bushing

Grease Fitting
Threaded King Pin Cap

FRONT AXLE

FIGURE 1

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GENERAL DESCRIPTION COMPONENTS

The J coach front and tag axles are nearly identical.
They are based on the same axle model and only have
slight variations. The major difference is that the tag axle Axle Beam
does not steer. The axles use the same steering The forged axle beam has a drop center and integral
knuckles and tie rod assembly. The tag axle tie rod is axle ends. The axle is rated at 16,500 lbs.
clamped to a lock plate that is rigidly mounted to the axle
beam. Front and tag axle alignment is adjustable.
The inspection, maintenance and lubrication
procedures are the same for both axles. Service
intervals are also the same.
NOTE: Any references to a steering arm, drag link or Do not repair the axle beam. It is heat-treated
and tempered. Failure to replace a damaged
other steering components do not apply to the tag
axle beam is unsafe and will void the warranty.
axle.

The front and axle assemblies are a forged beam

design with forged steel knuckle pin ends (Figure 1).
Axle ends are integral parts of the axle center beam. Steering Knuckles
Steering knuckles have grease fittings to lubricate the Steering knuckles are attached to the axle ends with
king pins and bushings. The bushings are of the “Easy straight king pins that are retained by draw keys.
Steer” type. Threaded king pin caps prevent dust and Knuckles are fitted with Easy Steer king pin bushings.
moisture from entering bushings. King pin bushing covers, spacers and seals prevent
The axle identification plate (Figure 2) is on the axle dust and moisture from entering the bushings.
center. Refer to the identification number when ordering Stop screws installed on the knuckles limit the wheel
parts. turn angle. All steering and wheel end components (tie
rod arms, brakes, wheel bearings and hubs) mount to
the knuckles.
IDENTIFICATION NO.

FH 945 CAX11 Tie Rod Assembly

The tie rod arms on both steering knuckles are
MODEL BRAKE VARIATION connected to the tie rod through tie rod ends. This
assembly maintains the correct steering geometry. The
tie rod assembly is adjustable and the ball joint ends are
FIGURE 2 greaseable.

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MAINTENANCE 5. Use a pry bar to lift the knuckle.

S The end play must measure between 0.001 and
0.025 inch (0.024 --- 0.635 mm) at all axle
positions.
S If the knuckle binds or the end play is zero,
Always wear eye protection during vehicle remove some shims from the shim pack. (See
maintenance and service procedures. Knuckle Installation.)
Support the coach with safety stands. Do not
S To decrease end play, add shims to the shim
work under a coach supported only by jacks.
pack. (See Knuckle Installation.)

INSPECTION
Regularly inspect the axle and components.

Routine Inspection
Always wear eye protection during vehicle
1. Replace worn or damaged fasteners. maintenance and service procedures.
2. Ensure that all fasteners are torqued to
Support the coach with safety stands. Do not
specification. (See Torque Chart.)
work under a coach supported only by jacks.
3. Inspect the axle and axle parts for wear or damage.
4. Check for bent or cracked parts.
5. Inspect the tires for wear patterns that indicate King Pin Bushings Inspection
suspension damage or misalignment.
1. Switch main battery disconnect OFF.
6. Replace all worn or damaged parts.
2. Lift the coach to access the axle.
7. Ensure that there is not excessive play or binding of
the pivot points. 3. Install safety stands. Do not work under a coach
supported only by jacks.
Steering Knuckle End Play Inspection 4. Upper King Pin Bushing: Install a dial indicator with
1. Switch main battery disconnect OFF. the base on the axle center and the tip against the
2. Lift the coach to access the axle. side of the top of the knuckle (Figure 4).
3. Install safety stands. Do not work under a vehicle
supported only by jacks.
4. Install a dial indicator with the base on the axle end
and the tip on the center of the king pin cap (Figure
3).

FIGURE 4

NOTE: If one bushing requires replacement, replace

FIGURE 3
both bushings in the knuckle.

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5. Move the top of the tire from side to side, towards 7. Push and pull on the bottom of the tire (Figure 7). If
and away from the vehicle (Figure 5). If the dial the dial indicator moves a total of 0.010 inch, the
indicator moves more than a total of 0.010 inch lower bushing is worn or damaged. Replace both
(0.25 mm), the upper bushing is worn or damaged. bushings. (See King Pin Bushing Installation.)
Replace both bushings. (See King Pin Bushing
Installation.)

FIGURE 7
FIGURE 5
6. Lower King Pin Bushing: Install a dial indicator with
the base on the axle end and the tip against the side
of the bottom of the knuckle (Figure 6).

FIGURE 6

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Tie Rod Inspection 4. Check for secure tie rod end nuts and cotter pins. If
Tie rod end inspection and replacement is necessary a pin is missing, torque the nut to specification and
to maintain vehicle alignment. Failure to replace worn tie install a new pin. Never back off a nut to install a pin.
rod ends will cause premature wear of steering and 5. Inspect the tie rod end boots for cracks or tears. If
suspension components, and will affect steering. either boot is damaged, replace both tie rod ends.
6. Mark the position of the tie rod.
7. Loosen the tie rod clamp nuts.

CAUTION 8. Rotate the tie rod back and forth 1/8 turn. (A pipe
wrench, with jaws protected, can be used.)
9. If the tie rod rotates freely, set it back to its original
Check the tie rod end play by hand. Do not use
position and torque the clamp nuts. If the tie rod
a pry bar; the readings from the dial indicator
will not be accurate and it could damage the binds, replace both tie rod ends.
tie rod end or give a false indication of wear. 10. From directly below the tie rod end, with both
hands, grab the tie rod as close to the end as
Always inspect the tie rod ends before
possible.
lubrication. After lubrication, the tie rod end
inspection will be compromised. 11. Push and pull on the rod several times.
12. If any movement is detected at either tie rod end,
replace both ends.

1. Block the rear wheels of the coach.

2. Lift the front end of the coach and install safety
stands. Do not work under a vehicle supported only
CAUTION
by jacks.
3. Turn the wheels to full left, then full right, then Always replace tie rod ends in pairs.
straight ahead.

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LUBRICATION Daily Wheel Bearing Oil Level Check

See Section 10: Lubrication. Check oil level daily or before each run. Lubricate
wheel bearings with hypoid gear oil or multi-grade gear
oil:
CAUTION 1. Check the level on the cap (Figure 9). If the oil is not
at the correct level:
Do not jack up the coach for lubrication. a. Remove the fill plug.
b. Add the specified oil until it is at the correct level.
King Pins, Tie Rod Assemblies and Ball Studs c. Install the fill plug.
Lubrication
Every 50,000 miles or twelve months lubricate king
pin bushings, tie rod ends and drag link ball studs with
multi-purpose grease S-16 or S-17:
1. King Pins: Clean grease fittings.
2. Lubricate the king pins through the grease fittings
on the top and bottom of the knuckle (Figure 8).
Apply until new lubricant comes out from the thrust
bearing seal and the upper shim pack.
3. Tie Rod and Drag Link Ends: Clean grease fittings.
4. Apply until new lubricant comes out from the boot.

FIGURE 9

Wheel Bearing Oil Change

Change wheel bearing oil regularly, when brakes are
relined or when oil seals are replaced, whichever comes
first. Lubricate wheel bearings with hypoid gear oil or
FIGURE 8 multi-grade gear oil.

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REMOVAL Knuckle Removal

1. Switch main battery disconnect OFF.
Tie Rod, Tie Rod Arms, Tie Rod Ends Removal
2. Lift the coach to access the axle.
3. Install safety stands. Do not work under a coach
supported only by jacks.
4. Vent the brake system and disconnect the air lines
Always wear eye protection during vehicle from the brake chambers.
maintenance and service procedures.
5. Remove the wheel. (Section 15)
Support the coach with safety stands. Do not
6. Remove the brake drum. (Section 4)
work under a coach supported only by jacks.
7. Remove the brake chamber, shoes and entire brake
1. Switch main battery disconnect OFF. assembly from the steering knuckle. (Section 4)
2. Lift the coach to access the axle. 8. Remove the hub cap and gasket.
3. Install safety stands. Do not work under a coach
supported only by jacks.
4. Remove the cotter pins and nuts from the tie rod
ends. CAUTION
5. Remove the tie rod assembly from the tie rod arms.
A removal tool may be required to pull the tie rod When tightening or loosening the wheel
ends from the tie rod arms. bearing adjusting nut, use the correct-sized
socket to avoid damaging the nut.
6. Remove the cotter pins and nuts that fasten the tie
rod arms to the knuckle.
7. Remove the tie rod arms from the knuckles. It may
be necessary to tap on the end of the arm with a 9. Remove the jam nut, jam nut lock washer, pierced
leather or plastic mallet to separate the arm from the lock ring and adjusting nut (Figure 11).
knuckle. Remove the key from the tie rod arm.
10. Remove the outer wheel bearing cone from the
8. If necessary, remove the tie rod ends from the tie rod hub.
as follows:
11. Remove the torque plate from the knuckle.
a. Mark the position where each tie rod end is
installed in the tie rod. (Figure 10) 12. Remove the hub.

FIGURE 10
FIGURE 11
b. Remove the tie rod clamp bolts.
c. Remove the tie rod ends.
13. Remove the tie rod arms and steering arm. (See
NOTE: Perform a front end alignment after tie rod Tie Rod, Tie Rod Arms, Tie Rod Ends Removal.)
ends are replaced. (See Section 2.) 14. Remove the king pin caps.

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15. Remove the threaded draw keys as follows:

To avoid serious personal injury and compo-

Do not hit steel parts with a steel hammer. The nent damage, operate the press according to
parts can break and cause serious injury. manufacturer’s instructions.

16. Use a brass drift and hammer (Figure 13) to

remove the king pins from the knuckle. If the king
CAUTION pin is difficult to remove, use a hydraulic king pin
remover.

Apply force squarely to the nut and the end

of the key, or the draw key will be damaged.

a. Loosen the lock nut and back it off until it is flush

with the end of the draw key.
b. Use a brass drift and hammer to hit the end of
the nut to loosen the draw key (Figure 12).
c. Remove the nut and draw key.

FIGURE 13

17. Remove the knuckle from the axle end.

18. Remove the shims, thrust bearing and seals from
the knuckle (Figure 14).

FIGURE 12

CAUTION
If the bushings are not being replaced, do
the following to prevent damage to the
bushings while removing the king pins:
1. Remove any flaring from the drift which
may touch the king pin.
2. Wrap tape around the end of the drift.
FIGURE 14

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19. If the knuckle bushings are damaged, remove the c. Use a king pin bushing tool to remove the
bushings as follows: bushings. (See Service Tools.)
a. Remove and discard the upper and lower king d. Install the tool in the upper king pin bushing.
pin seals (Figure 15). e. Press the top bushing from the knuckle (Figure
16).

FIGURE 15
b. Put the knuckle on the press. FIGURE 16

NOTE: Use a press with a 5 ton (4500 kg) capacity, f. Install the tool in the lower king pin bushing.
and ensure that the knuckle does not move when the g. Press the bottom bushing from the knuckle
bushings are removed. (Figure 16).

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CLEANING AND PARTS INSPECTION solution. The parts must stay in the hot solution tanks
until they are completely cleaned and heated.
Drying Cleaned Parts
Parts must be dried immediately after cleaning. Dry
the parts with clean paper or rags, or with compressed
Do not repair the axle beam or knuckles. air. Do not dry bearings with compressed air.
These components are heat-treated and tem-
pered. Failure to replace damaged or out-of- Corrosion Prevention on Cleaned Parts
specification components is unsafe and voids Apply light oil to undamaged, cleaned and dried parts
the warranty. that are to be assembled immediately. DO NOT apply oil
to brake linings.
Always wear eye protection when performing
vehicle maintenance or service. If parts are to be stored, apply a corrosion inhibitor to
all surfaces. DO NOT apply this material to brake linings.
Do not weld any steering or axle components. Store parts in paper or another material that prevents
Do not bend knuckles or any steering or axle corrosion.
components.
NOTE: Ensure that all tapered parts are clean and
Do not drill out the knuckle pin holes. dry, with no lubricant or corrosion preventative
applied to mating surfaces.
Do not drill out draw key holes.
Do not spray weld bearings or bores. Parts Inspection
Always follow manufacturer’s instructions Carefully inspect disassembled parts before reusing
when using cleaning solvents, hot solution them. Refer to the following guidelines:
tanks and alkaline solutions. Do not use gaso- 1. Inspect and replace any parts that are worn,
line to clean parts; gasoline can explode. cracked or damaged. Check for cracks using dye
penetrant or magnetic particle testing methods.
2. Measure the king pin bushing inside diameter using
Cleaning Ground or Polished Parts a micrometer and telescoping gauge (Figure 17).
Use cleaning solvent to clean ground or polished
parts and surfaces. Kerosene and diesel fuel can be
used for this purpose. DO NOT use gasoline.

CAUTION
Do not clean ground or polished parts in a
hot solution tank or with water, steam or
alkaline solutions. These solutions will
corrode the parts.

FIGURE 17
Cleaning Rough Parts
Rough parts can be cleaned with the same solvents Replace the bushing if the average inside diameter
as ground and polished parts. Rough parts can also be measurement is beyond the specifications in in
cleaned in hot solution tanks with a weak alkaline Table 1.

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3. After removing a worn bushing, measure the

knuckle bore inside diameter in two locations.
Always use a micrometer and telescoping gauge
when taking knuckle bore measurements. Some
rounding of the top and bottom bore edges is
acceptable.
Measure the bore in two positions (90_ opposed)
and at two depths on both upper and lower bores (8
measurements). If the average measurement
exceeds the knuckle bore specification in Table 1,
replace the knuckle (Figure 18).

FIGURE 19

Replace the axle if the average measurement is

greater than the axle beam bore maximum
diameter shown in Table 1.
5. Inspect the taper on the tie rod arm for wear or
damage, replace the arm as required.
6. Inspect the taper in the lower knuckle boss for wear
or damage, replace the knuckle as required.
7. If the king pin has worn through the bushing and
into the knuckle, replace the knuckle.
NOTE: If any part of the linkage is loose, check all the
pivot points. Check the pivot points when the linkage
is lubricated.

8. Ensure that all pivot points in the steering linkage

are tight.
FIGURE 18 9. Inspect the thrust bearing and seal for wear or
damage. Replace parts that are worn or damaged.

Table 1: Axle Wear Limit Specifications

Maximum Diameter
Follow this procedure for both the upper and lower
knuckle bores. If either bore’s diameter exceeds the Knuckle Bore 1.922” (48.82 mm)
limits in Table 1, remove and replace the knuckle.
Axle Beam Bore 1.798” (45.67 mm)
4. Measure the inner bore diameter of the axle beam. King Pin Bushing Bore 1.795” (45.59 mm)
Some rounding at the top and bottom of the beam is
acceptable. Tie Rods and Tie Rod Ends Inspection
Measure the axle beam bore in two positions (90_ 1. Inspect the tie rod for wear and damage. Replace
opposed), and at two specific locations: 0.5 inch the tie rod if it is worn or damaged.
(12.7 mm) below the top of the bore, and 0.5 inch 2. Inspect the tie rod ends for wear and damage.
(12.7 mm) above the bottom of the bore (Figure 19). Replace both if either one is worn or damaged.

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Wheel Bearings Inspection

Inspect the wheel bearings when the knuckle is
inspected or repaired.
1. Remove all lubricant from the bearings, knuckle,
hub and hub cap.

WORN RADIUS

FIGURE 22

WORN SURFACE

FIGURE 20
2. Inspect the bearings for damage. Replace entire
bearing if:
a. rollers have:
S the centre of the large end worn level or below FIGURE 23
the other surface (Figure 20).
S the radius at the large end worn to a sharp
edge (Figure 20).
S etching, pitting or any other damage.
b. cup or cone surfaces have:
S any visible grooves (Figure 21).
S cracks or breaks (Figure 21).
S etching or pitting (Figure 22).
S spalling, flaking or any other damage.
c. roller cage has bright wear marks or any other
damage (Figure 23).

FIGURE 24

FIGURE 21

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INSTALLATION

0.148” - 0.178”
(3.8 - 4.5 mm)

Always wear eye protection during vehicle

maintenance and service.
To avoid personal injury and component dam-
age, operate the press according to the
manufacturer’s instructions.
0.148” - 0.178”
(3.8 - 4.5 mm)
Steering Knuckle Bushing Installation
1. Install the top knuckle bushing first.
2. Place the knuckle in the press so that the bores are
in line with the press. The upper knuckle boss must FIGURE 26
be toward the press.
10. Ream the bushingS. (See Reaming Knuckle
3. Place the bushing in the bore.
Bushings.)
4. Use the installation tool to initially press the bushing
approximately 0.125 inch (3 mm) into the bore. Reaming Knuckle Bushings
Ensure that the bushing is being pressed straight
into the bore (Figure 25). NOTE: This procedure requires a bushing reaming
tool as shown in Service Tools.

0.125” (3 mm)
INITIAL INSTALLATION DEPTH
CAUTION
Ream only with a fixed reamer. Do not hone
or burnish the bushings.

1. Put the knuckle in a vise with brass jaws.

2. Slide the pilot of the reamer tool through the top
bushing in the knuckle until the reamer blades
touch the bushing (Figure 27).

FIGURE 25

5. Press the bushing into the bore until the bottom of

the bushing is 0.148 to 0.178 inch (3.8 to 4.5 mm)
from the bottom of the knuckle bore (Figure 26).
6. Turn the knuckle upside down to install the lower
bushing. Ensure that the bores are in line with the
press.
7. Place the bushing in the bore.
8. Use the installation tool to initially press the bushing
approximately 0.125 inch (3 mm) into the bore.
Ensure that the bushing is being pressed straight
into the bore (Figure 25).
9. Press the bushing into the bore until the bottom of
the bushing is 0.148 to 0.178 inch (3.8 to 4.5 mm)
from the bottom of the knuckle bore (Figure 26). FIGURE 27

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3. Rotate the reamer tool while applying a slight Inner Knuckle Bushing Seals
downward pressure. Rotate the reamer tool 1. To install the upper seal, place the knuckle upside
smoothly. down in a vise with brass jaws, holding the top of the
4. When the reamer is almost through the top bushing, knuckle securely.
support the tool so that it does not drop to the 2. Place the seal in the the knuckle bore. Ensure that
bottom bushing. the lip of the seal is away from the bore (Figure 29).
5. After the reamer is through the top bushing, guide it
into the bottom bushing. Repeat steps 3 and 4 for
the bottom bushing (Figure 28).

(PUSH DOWN LIGHTLY)

REAM LOWER
BUSHING SECOND

TOP OF KNUCKLE

FIGURE 29

FIGURE 28

6. Slide the reamer tool out the bottom of the bottom

Do not hit steel parts with a steel hammer. The
bushing.
parts can break and cause personal injury.
NOTE: If you must remove the reaming tool through
the top of the bushing, rotate the tool in the opposite 3. Use a brass drift, hammer and correct size driver to
direction as you remove it. install the seal. Install the seal until the seal is flush
with the knuckle’s machined surface (Figure 29).
7. Clean all material from the bushings, knuckle and 4. Turn the knuckle over to install the lower seal.
king pin cap threads. 5. Repeat steps 2 and 3 for the other seal.

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Knuckle Installation
1. Clean the bores of the knuckle and the axle end.
2. Place the knuckle on the axle end.
NOTE: The one-piece thrust bearing with integrated
grease seal is completely interchangeable with the
two-piece design. It has a specified top and bottom
orientation:

a. The surface with the inner diameter seal must

face up.
b. The surface with the outer diameter seal must
face down (Figure 30).

TOP INNER DIAMETER SEAL

FIGURE 31

TOP
Wear gloves when holding shims. Shims have
sharp edges.

4. Install the shim pack as follows:

INTEGRATED GREASE SEAL BOTTOM a. Inspect the shims and replace any damaged
ones.
FIGURE 30 b. If a new shim pack must be used, select the
3. Slide the thrust bearing between the bottom of the number of shims that will give end play between
axle end and the knuckle. If a separate seal and 0.001 and 0.025 inch (0.025 --- 0.630 mm).
bearing are used, ensure that the seal is toward the c. Place a pry bar between the steering arm boss
axle center and over the thrust bearing (Figure 31). and the axle beam. Lift the knuckle and slide the

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shim pack between the top of the axle and the c. Rotate the king pin so that the draw key slots in
knuckle (Figure 32). the pin are aligned with the holes in the axle end.

CAUTION
Do not force the pin through the top bushing
because this will damage the shims.

d. Push the king pin through the top bushing,

bushing seal and shim pack. If the pin is difficult
to install, check that all the parts are aligned
properly.
e. After the king pin is through the shim pack, push
the king pin into the bottom bushing. If
FIGURE 32 necessary, use a brass hammer to drive the king
pin into the bushing. Ensure that the axle end,
d. Align the bores of the knuckle, axle end, shims,
knuckle, thrust bearing and the bushing seal are
seals and thrust bearing. If these parts are not
aligned.
aligned, installing the king pin will damage
parts. f. Ensure that the draw key slots in the king pin are
5. Install the king pin as follows (Figure 33): aligned with the holes in the axle end.
a. Apply the specified grease to the bottom half of NOTE: Do not drive the draw keys into the knuckle
the king pin. until after the end play is checked and adjusted.
b. Install the king pin in the top of the knuckle.
Ensure that “TOP” (stamped on the king pin) is 6. Install the top draw key in front of the axle end. Install
facing you. the bottom draw key behind the axle end. Ensure
that the key goes through the slot in the pin. Lightly
tap the draw keys into the axle center (Figure 34).

FIGURE 33 FIGURE 34

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7. Measure the knuckle end play as shown in Steering

THREADED
Knuckle End Play. Note that without the king pin KING PIN CAP
caps installed, the tip of the indicator must contact 100-120 FT-LB
another part of the knuckle. The king pin is mounted 135-160 Nm
to the axle and and will not show any deflection.
Adjust shim pack as necessary.

CAUTION
Ensure that the draw keys are installed
completely and the locknuts are torqued. If
the draw keys are not correctly installed, the
king pin and axle end will be damaged. FIGURE 36

8. Install the locknuts on the threaded draw keys and 10. Connect the tie rod arm to the knuckle. (See Tie
torque them to 30 to 45 lb-ft (41-61 Nm) (Figure 35). Rod Arm Installation.)
11. Install hub and wheel bearings onto the spindle.
Locknut (See Section 15).
30-- 45 lb-ft 12. Adjust the wheel bearings. (See Adjustments:
41-- 61 Nm Wheel Bearings.)
13. Install the hubcap and gasket on the knuckle.
Torque the capscrews to 20 to 30 lb-ft (28 to 40 Nm).
Torque the screws on plastic hubcaps to 15 to 18
lb-ft (21 to 24 Nm).
14. Add oil to the hub to the proper level. (See
Lubrication in this section.)
15. Install the brake chamber and brake assembly.
(Section 4.)
FIGURE 35 16. Install the tire and wheel assembly (Section 15).
9. Apply thread sealant around the first thread of the 17. Lower the vehicle to the ground. Check the brake
king pin caps. Install the caps and torque to 100 to operation.
120 ft-lb (135 to 160 Nm) (Figure 36). 18. Check and adjust the toe-in. See Section 2.

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Tie Rod Arm Installation Tie Rod and Tie Rod End Installation
1. With the key in the slot, insert the tie rod arm into the
knuckle.
NOTE: The tie rod has right-hand threads on one end
NOTE: Do not mix arm key and slot types. The square and left hand threads on the other. Ensure that the
key is positioned flush to the shoulder of the arm ends are installed correctly.
taper. The woodruff key is positioned in the slot
provided.
1. If they have been removed, install the tie rod ends
on the tie rod. Install the tie rod ends to the positions
marked before their removal. Thread the tie rod
CAUTION ends equally on each side of the tie rod to the overall
required length.
Tighten the tie rod arm nuts to the specified 2. Install the clamps on the tie rod. Tighten the clamp
torque. Failure to use the proper torque will nuts to 40 to 60 lb-ft (55 to 81 Nm).
damage the tie rod arm, Pitman arm or
3. Clean and dry the tie rod taper and tie rod arm taper
knuckle.
hole.
4. Install the tie rod ends into the tie rod arms.
2. Install the tie rod arm nut: For 1.125”-12 thread,
5. Torque the tie rod end nuts.
torque to 550 to 740 lb-ft (745 to 1003 Nm).
3. Install the cotter pins. If the holes are not aligned, 6. Install the cotter pins. If the holes are not aligned,
tighten the nut to the next hole. Do not loosen nuts tighten the nut to the next hole. Do not loosen nuts
to install the cotter pin. to install cotter pins.
4. Check and, if necessary, adjust the toe-in. 7. Check and, if necessary, adjust the toe-in.

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ADJUSTMENTS 10. Bend the lock washer off the flats of the jam nut
and remove the jam nut, jam nut washer and
Wheel Bearings pierced lock ring (Figure 38).

Support the coach with safety stands. Do not

work under a vehicle supported only by jacks.

1. Ensure that the vehicle is on a level surface.

2. Block the coach.
3. Lift the axle for the wheels to be serviced. Install
safety stands. Do not work under a vehicle
supported only by jacks. FIGURE 38
4. Drain all oil from the hubcap.
5. Remove the wheel and tire assembly from the hub. NOTE: When removing or installing adjusting nuts,
If the brake drum remains, ensure that is is securely use the correct wrench socket to avoid damaging the
fastened. nuts.
6. Remove the hubcap.
7. Attach a dial indicator with the magnetic base at the
bottom of the hub.
8. Adjust the dial indicator so that the pointer is against
CAUTION
the center of the spindle (Figure 37).
Do not strike the adjusting nut with a metal
hammer, chisel or drift to loosen the
adjusting. This will damage the nut.

11. Use a torque wrench to tighten the adjusting nut to

100 lb-ft (136 Nm) while rotating the hub in both
directions.
12. Loosen the nut completely and then tighten it to 20
lb-ft (27 Nm) while rotating the hub.
13. Adjust the wheel bearing as follows (Figure 38):
a. Back off the adjusting nut 1/3 turn.
b. Install the pierced lock ring, lock washer and
FIGURE 37 jam nut.
c. Torque the jam nut to 200 to 300 lb-ft (271 to 407
Nm).
d. Measure the wheel end play. If it is not between
NOTE: Do not push or pull on the top and bottom of 0.001---0.005 inch (0.025---0.127 mm), repeat
the hub or the reading will be false. steps a to c. If the end play is too large, only back
off the adjusting nut 1/4 turn.
9. Measure the end play by pushing and pulling on e. When the proper play is achieved, lock the jam
both sides of the hub while looking at the dial nut in place by bending the edge of the jam nut
indicator. The end play is the total travel observed. If lock washer over one flat of the jam nut.
the end play is between 0.001 and 0.005 inches f. Measure the end play again. If the total travel is
(0.025 --- 0.127 mm), go to step 15. If not, continue not within specifications, repeat the wheel
with the following steps to adjust the wheel bearing. bearing adjustment.

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14. Install the gasket and cap on the hub. Install the e. Torque the jam nut on the stop bolt to 50 to 65
capscrews and torque to 20 to 30 lb-ft (27 to 41 Nm). lb-ft (68 to 88 Nm).
Torque the screws on the plastic hubcaps to 15 to f. Turn the wheels to the left until the widest part of
18 lb-ft (20 to 24 Nm). the inside sidewall on the left front tire clears the
15. Install the wheel. left hand lower shock mount by one inch (25
16. Lower the vehicle and check brake operation. mm).
17. Refill the oil lube hub reservoir. (See Lubrication in g. Run the left hand knuckle’s stop bolt out until it
this section.) contacts the boss on the axle beam.
h. Torque the jam nut on the stop bolt to 50 to 65
Steering Stop Adjustment
lb-ft (68 to 88 Nm).
The steering stop adjustment controls the vehicle’s
maximum turn angle.
1. Set the parking brake.
2. Set the axle stops as follows: CAUTION
a. Loosen the jam nut on the axle’s stop bolts.
b. Turn in the stop bolts. Do not increase the vehicle’s maximum
specified turn angle. If the angle is
c. Turn the wheels to the right until there is one inch increased, the steering arm, tie rod and tie
(25 mm) of clearance between the inside front rod ends will be damaged.
edge of the left hand front tire and the drag link.
The hydraulic steering pressure should
d. Turn the right hand knuckle’s stop bolt out until it
relieve (drop off) at the end of the steering
contacts the boss on the axle beam (Figure 39). stroke. If the pressure does not relieve, the
axle components will be damaged.

Pressure Relief Adjustment

The pressure relief adjustment in the power steering
system stops or reduces the force applied to the steering
arm when the wheel approaches full turn position. The
power steering gear pressure relief valves set
BOSS themselves to the steering stops the first time the coach
is steered from stop to stop.
JAM NUT STOP BOLT Check the pressure relief if the steering arm is
damaged or the power steering gear is serviced. (See
FIGURE 39 Section 11D: Steering Gear TAS-85 Series.)

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TROUBLESHOOTING
Condition Cause Correction
Tires wear out quickly or 1. Incorrect tire pressure 1. Put specified pressure in tires
have uneven tire wear 2. Out-of-balance tires 2. Balance or replace the tires
3. Incorrect tag axle alignment 3. Align the axle tandems
4. Incorrect toe-in setting 4. Adjust the toe-in to the proper setting
5. Incorrect steering arm geometry 5. Service the steering system as needed
6. Excessive wheel end play 6. Adjust the wheel bearings
Vehicle is hard to steer 1. Low power steering system pressure 1. Repair the power steering system
2. Steering gear incorrectly assembled 2. Assemble the steering gear correctly
3. Steering linkage needs lubrication 3. Lubricate the steering linkage
4. King pins are binding 4. Replace the king pins
5. Incorrect steering arm geometry 5. Service the steering system as needed
6. Caster out of adjustment 6. Adjust the caster as needed
7. Tie rod ends stiff 7. Replace the tie rod ends
8. Worn thrust bearing 8. Replace the thrust bearing
Tie rod ends are worn 1. The tie rod ends need lubrication 1. Lubricate the tie rod ends. Follow the
2. Severe operating conditions lubrication schedule
3. Damaged boot on the tie rod end 2. Operate the vehicle correctly
4. Add-on power steering system not 3. Replace the tie rod end
installed correctly 4. Install the power steering cylinders
correctly
Bent or broken tie rod, 1. Too much pressure in the power 1. Adjust the power steering system to
ball stud, steering arm steering system the specified pressure
or tie rod arm 2. Power steering system relief 2. Adjust the power steering system to
pressure setting out of adjustment the specified pressure
3. Vehicle not operated correctly 3. Make sure the vehicle is operated
correctly
4. Add-on power steering system not 4. Install the power steering system
installed correctly correctly
Worn or broken steering 1. Drag link fasteners tightened past the 1. Tighten the drag link fasteners to the
ball stud specified torque specified torque
2. Lack of lubrication or incorrect 2. Lubricate the linkage to specification
lubricant 3. Adjust the stops to the specified
3. Wheel stops or relief pressure dimension
settings out of adjustment
Worn king pins or 1. Worn or missing seals and gaskets 1. Replace the seals and gaskets
bushings 2. Incorrect lubricant 2. Lubricate with the proper lubricant
3. Axle not lubricated at the scheduled 3. Lubricate the axle at the specified
frequency frequency
4. Incorrect lubricating procedures 4. Use correct lubrication procedures
5. Lubrication schedule does not match 5. Change the lubrication schedule to
operating conditions match the operating conditions
Vibration or shimmy in 1. Caster out of adjustment 1. Adjust the caster
axle during operation 2. Wheels and/or tires out of balance 2. Balance or replace the wheels or tires
3. Worn shock absorbers 3. Replace the shock absorbers
4. Worn radius rod bushings 4. Replace bushings

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 Date March 2003 Page 1-23

TORQUE CHART

3
6 1

2
4
1

Item Description Axle Size Lb-Ft Nm

1 Tie rod arm nut Front, Tag 1.125” - 12 550 - 740 745 - 1003
2 Tie rod end nut Front, Tag 0.875” - 14 160 - 300 217 - 406
3 Threaded king pin cap Front, Tag 2.00” 100 - 120 135 - 160
4 Steering arm nut Front 1.250” - 12 775 - 1450 1051 - 1935
Stop screw lock nut Front 0.500” - 20 50 - 65 68 - 88
5 Tie rod clamp lock nut Front, Tag 0.625” - 11 40 - 60 55 - 82
6 Draw key nut Front, Tag 0.4375” - 20 30 - 45 41 - 61
Tie rod lock plate clamp Tag 100 136

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SERVICE TOOLS

SOME TOOLS LISTED IN THIS SECTION ARE NONSTANDARD. THEY ARE

AVAILABLE FOR PURCHASE THROUGH MCI SERVICE PARTS OR, WHERE
PRACTICAL, MAY BE MANUFACTURED BY THE OPERATOR. IN THESE
CASES, DRAWINGS ARE AVAILABLE UPON REQUEST.

2.5”
8.00” MIN. (205 mm)
(63 mm)

1.780” ± 0.001 1.912” ± 0.001

(45.21 ± 0.02 mm) (45.56 ± 0.02 mm)

20-- 5 Tool - King Pin Bushing Removal & Installation

1.780” ± 0.001” 1.7955” ± 0.0005” 1.790” ± 0.001”

(45.21 ± 0.02 mm) (45.606 ± 0.012 mm) (45.46 ± 0.02 mm)

10.25” 2.5” 12.25”

(260.4 mm) (63 mm) (312 mm)
MINIMUM

20-- 312 Tool - King Pin “Easy Steer” Bushing Reamer

SPECIAL TOOL
Kent-Moore King Pin Remover Part No.: J36136
NOTE: Kent-Moore tools are available from MCI Service Parts.

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SPECIFICATIONS

ALIGNMENT DATA (LOADED)*

Camber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (Acceptable Range) --0.19 to +0.68 Degrees
Caster . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.0 Degrees (Positive)
Toe-In (Adjustable) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.03 in. ± 0.03 inches
Track . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84.9” (2156 mm)

* Note: Based on empty coach front axle weight of 10,000 lbs.

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 Date March 2003

SECTION 2
REAR AXLE
A -- Drive Axle
B -- Tag Axle
C -- Alignment Procedure

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SECTION 2A
DRIVE AXLE
CONTENTS OF THIS SECTION
SUBJECT PAGE
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2A-2
Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2A-2
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2A-2
Lubrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2A-2
Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2A-3
Axle Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2A-3
Differential Carrier Failure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2A-3
Drive Axle Removal and Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2A-3
Carrier Repair --- Removal and Disassembly . . . . . . . . . . . . . . . . . . . . . 2A-3
Fasteners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2A-13
Axle Welding Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2A-14
Ring Gear and Drive Pinion Set --- Adjustment and Assembly . . . . . . 2A-15
Pinion Cage Shim Pack Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2A-20
Differential Gear Set Adjustment and Installation . . . . . . . . . . . . . . . . . . 2A-26
Torque Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2A-36
Service Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2A-37
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2A-39

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GENERAL DESCRIPTION Change axle gear oil every:

S 100,000 miles (160,000 km) if using
The drive axle is a full floating type with pressed steel petroleum-based oil.
housing and oil-lubricated wheel bearings. A magnetic
drain plug is installed in the bottom of the housing. or
Available drive axle ratios are 4.30:1 and 4.56:1. S 250,000 miles (400,000 km) if using synthetic oil.
The single reduction carrier has hypoid drive pinion Drive axle wheel bearings are lubricated by the axle’s
and ring gear. The differential and gear assembly is gear oil.
mounted on tapered roller bearings and lubricated by
the differential oil.
The straddle-mounted pinion has two tapered roller
bearings in front of the pinion teeth that take the axial
loads, and a third bearing behind the pinion teeth to Follow safe shop practice. Always wear eye
carry the radial load. protection during maintenance and service
An identification tag is on the axle housing or the procedures.
differential carrier. Use the model number and the ratio
number marked on the tag to order replacement parts.
Drive Axle Oil Change
COMPONENTS The drive axle uses splash lubrication to distribute the
oil to axle components. A short time is required for oil to
Axle Housing reach all areas of the axle.
The hot formed rectangular axle housing is designed 1. Remove the fill and drain plugs (Figure 1).
with full corner sections for strength and rigidity. The
2. Allow the oil to drain completely.
other axle components assemble to this part.
3. Clean the magnetic drain plug and install. Torque to
Differential Carrier 25 - 35 lb-ft (34 - 47 Nm) minimum.
The single reduction carrier is front mounted into the 4. Fill the axle with the specified lubricant to the bottom
axle housing. The carrier has a hypoid drive pinion and edge of the fill hole.
ring gear set, and bevel gears in the differential 5. Reinstall the fill plug. Torque to 35 - 47 lb-ft (47 - 63
assembly. The drain plug is magnetic to catch metallic Nm) minimum.
particles.
6. Lubricate the universal joints.
Wheel Bearings 7. Drive the coach, unloaded, for two miles (3 km) at
The axle hubs have oil-lubricated wheel bearings. under 25 mph (40 kph) to thoroughly lubricate the
assembly.

MAINTENANCE

LUBRICATION
NOTE: Also see Section 10: Lubrication.

NOTE: Lubrication intervals are given for intercity

coaches. For higher-use coaches, gear oil must be
checked and changed more frequently.

Lubrication Intervals
DRAIN FILL
Check gear oil level every 25,000 miles (40,000 km) or
at the fleet maintenance interval, whichever comes first.
Inspect the oil for unusual physical characteristics such FIGURE 1
as dirty appearance, gritty texture or frothy consistency.

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INSPECTION 4. Disconnect the sway bar links. See Section 12.

Every 50,000 miles (80,000 km) or 6 months, 5. Disconnect the brake chamber air lines.
whichever comes first, inspect as follows:
6. Disconnect the propeller shaft. See Section 14.
Fasteners
7. Disconnect both height control valve links from
1. Replace worn or damaged fasteners.
brackets, and pull down on each height control
2. Ensure that all fasteners are torqued to valve arm to exhaust air from the air springs.
specification. (See Torque Chart.)
8. Remove both ends of all four radius rods. See
Wear and Damage Section 12.
1. Inspect the axle and axle parts for wear or damage.
9. Remove shock absorbers.
2. Look for bent or damaged parts.
10. Disconnect air springs from the suspension
3. Inspect the tires for wear patterns that may indicate
supports.
suspension damage or misalignment.
4. Replace all worn or damaged parts. 11. Lower the axle and carefully remove it from the
coach body.
AXLE REPAIR
Certain weld repairs may be made to the axle Drive Axle Installation
housing. Do not bend or straighten the axle housing.
Damaged drive axle housings should be replaced. Reverse the steps of the removal procedure.

NOTE: Refer to the welding caution in the

introductory pages of this manual before starting any CARRIER REPAIR
welding operation. The single reduction differential carrier (Figure 2) is
front mounted into the axle housing. The carrier ensures
Weld repairs are only allowed on existing axle housing normal differential action between the wheels.
welds of the following types:
1. Cover welds.
Carrier Assembly Removal
2. Housing seam welds between the suspension
attaching brackets. 1. After the axle has been removed from the coach,
The differential carrier and axle shafts must be support it securely under the axle shaft housings.
removed before welding the axle housing. Support the axle at a height sufficient to allow a
roller jack to pass under the axle center.
DIFFERENTIAL CARRIER FAILURE 2. Remove the plug from the bottom of the axle
If the differential is noisy, it needs to be repaired. housing and drain lubricant from the assembly.
DRIVE AXLE 3. Remove the stud nuts and washers from the flanges
of both axle shafts.
Drive Axle Removal
1. Block front wheels of the coach to prevent rolling. 4. Loosen the tapered dowels in the flanges of both
axle shafts as follows:
2. Switch the battery disconnect OFF and vent the air
system.
3. Raise the rear end of the coach with jacks until the
bottom of the body is approximately 18” (450 mm)
from the ground. Block the body in this position.
(See Section 3 --- Coach Jacking Points.)
Follow safe shop practice. Wear safety
glasses. Do not hit the round driving lugs on
the head of the axle shafts. Lugs can break and
CAUTION cause injury.

Do not allow the rear axle assembly to hang on a. Hold a 1!@2-inch-diameter brass drift or brass
the air springs. Damage to the air springs may hammer against the center of the axle shaft,
result. inside the round driving lugs (Figure 3).

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1
2 3
6 7 4
5 34
33

30 31
32 29
28
8 9

10

11 13
12 14
15 16 27
26
23 25
17 24
22
19

18
22 23
20 21 24
51 50
52
53
SINGLE REDUCTION DIFFERENTIAL CARRIER 49
48
45
44
46
45 46
48
35

36
37

38
45
46
47
46
43 44 45
42

39 41
40

FIGURE 2

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b. Hit the end of the drift with a five to six pound 7. Remove all but the top two carrier-to-housing
hammer and the axle shaft and tapered dowels capscrews or stud nuts and washers.
will loosen.
8. Loosen the top two carrier-to-housing fasteners but
leave them attached to hold the carrier in the
housing.
9. Loosen the differential carrier in the axle housing.
Use a leather mallet to tap the mounting flange of
the carrier at several points.
10. After the carrier is loosened, remove the top two
fasteners. Carefully remove the carrier from the axle
housing using the hydraulic roller jack.

CAUTION
FIGURE 3 Be careful not to damage the carrier or
housing flange. Damage to these surfaces will
cause oil leaks.
CAUTION
Do not use a chisel or wedge to loosen the
axle shafts and dowels. The chisel or wedge 11. Lift the differential carrier by the input yoke and put
can damage the hub, axle shafts and oil seals. the assembly in a repair stand (Figure 5). (See
Service Tools.) Do not lift the carrier assembly by
hand; use a lifting tool.
5. Remove the tapered dowels and both axle shafts
from the axle.
6. Place a hydraulic roller jack under the differential
carrier to support the assembly (Figure 4).

FIGURE 5
FIGURE 4

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Differential and Ring Gear Removal 2. Mark one carrier leg and bearing cap for the
purpose of matching the parts when reassembling
NOTE: Before starting work on the differential carrier,
the carrier. A center punch and hammer can be
inspect the hypoid gear set for damage. If there is no used to mark the parts (Figure 8).
damage, reuse the gear set. Use a dial indicator to
measure the backlash of the gear set (Figure 6) and
write it down. This measurement will be needed when
the gear set is reinstalled.

FIGURE 8

FIGURE 6 3. Remove the bearing adjusting rings cotter keys

(Figure 9).
1. Remove the thrust screw and jamnut from the
differential carrier (Figure 7).

FIGURE 9
FIGURE 7

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4. Remove the bearing cap capscrews and washers

(Figure 10).

FIGURE 12

Differential and Ring Gear Disassembly

FIGURE 10 NOTE: The differential normally does not require
servicing unless a problem is suspected.

5. Remove the bearing caps and bearing adjusting 1. If the match-marks on the case halves of the
rings from the carrier (Figure 11). differential assembly are not visible, mark each
case half with a center punch and hammer. The
marks ensure that the plain half and flange half are
correctly assembled (Figure 13).

FIGURE 11

FIGURE 13
6. Lift the main differential and ring gear assembly
from the carrier. Put the assembly on a work bench 2. Remove the bolts, nuts and washers that hold the
(Figure 12). case halves together.

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Follow safe shop practice. Wear safety

glasses. Do not hit steel parts with a steel
hammer. Parts can break and cause injury.

3. Separate the case halves. If necessary, use a brass,

plastic or leather mallet to loosen the parts.
4. Remove the differential spider, four pinion gears,
two side gears and six thrust washers from inside
the case halves (Figure 14).

FIGURE 15

7. If the differential bearings need replacement,

remove the bearing cones from the case halves.
Use a bearing puller or press (Figure16).

FIGURE 14
5. If the ring gear needs to be replaced, remove the
bolts, nuts and washers that hold the gear to the
flange case half.
6. Separate the case half and ring gear using a press.
Support the assembly under the ring gear with
metal or wood blocks and press the case half
through the gear (Figure 15). FIGURE 16

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Drive Pinion and Bearing Cage Removal 4. Remove the capscrews and washers that hold the
1. Using a yoke bar on the input yoke to hold the drive bearing cage in the carrier (Figure 19).
pinion in position, remove the nut and washer from
the drive pinion (Figure 17).

FIGURE 19
FIGURE 17
5. Remove the drive pinion, bearing cage and shims
2. Remove the yoke bar. from the carrier. If the bearing cage is tight in the
3. Remove the yoke from the drive pinion. If the yoke is carrier, hit the bearing cage at several points around
tight, use a puller for removal (Figure 18). the flange areas with a leather, plastic or rubber
mallet (Figure 20).

Follow safe shop practice. Wear safety

glasses. Do not hit steel parts with a steel
hammer. Parts can break and cause injury.

YOKE PULLER

FIGURE 18

CAUTION
Do not use a hammer or mallet to loosen the
yoke. A hammer or mallet can damage the
parts and cause runout or alignment problems.
FIGURE 20

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CAUTION
Do not use a pry bar to remove the bearing
cage from the carrier. A pry bar can damage
the bearing cage, shims and carrier.

Wear gloves when handling shims. Shims

have sharp edges and can cause injury.

6. If the shims are in good condition, keep the shims FIGURE 22

for reuse when the carrier is reassembled.
7. If shims are to be discarded, measure the thickness NOTE: The inner bearing cone and bearing spacer
of the pack. Record the dimension to calculate the will remain on the pinion shaft.
depth of the drive pinion in the carrier when the gear
set is installed. 2. If a press is not available, use a leather, plastic or
Drive Pinion and Bearing Cage Disassembly rubber mallet to drive the pinion through the
1. Put the drive pinion and bearing cage in a press bearing cage.
(Figure 21). 3. If the pinion seal is mounted directly in the outer
bore of the bearing cage, remove the seal at this
time. Use a screwdriver or small pry bar for removal.
After the seal is removed, lift the outer bearing cone
from the cage (Figure 23).

FIGURE 21
The pinion shaft must be toward the top of the
assembly. Support the bearing cage under the flange
area with metal or wood blocks. Press the drive pinion
FIGURE 23
through the bearing cage (Figure 22).

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CAUTION
Take care when using a screwdriver or pry bar
to remove the seal. Do not damage the bore
wall. Damage to the bore can cause oil leaks.

4. If the pinion bearings need to be replaced, remove

the inner and outer bearing cups from the inside of
the cage. Use a press and sleeve, bearing puller or
a small drift and hammer. When a press is used,
support the bearing cage under the flange area with
metal or wood blocks (Figure 24).
FIGURE 25
6. If the spigot bearing needs to be replaced, put the
drive pinion in a vise. Install a soft metal cover over
each vise jaw to protect the drive pinion.
7. Remove the snap ring from the end of drive pinion
with snap ring pliers that expand (Figure 26).

FIGURE 24

5. If the pinion bearings need to be replaced, remove

the inner bearing cone from the drive pinion with a FIGURE 26
press or bearing puller. The puller MUST fit under
the inner race of the cone to remove the cone 8. Remove the spigot bearing from the drive pinion
without damage (Figure 25). with a bearing puller (Figure 27).

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Cleaning Axle Assemblies

1. A complete axle assembly can be steam cleaned on
the outside to remove dirt. Close all openings such
as breathers or vents in air chambers before steam
cleaning the axle assembly.

Drying Cleaned Parts

1. Parts must be dried immediately after cleaning.
2. Dry the parts using soft, clean paper or cloth rags.
3. Except for bearings, parts can be dried with
compressed air.

FIGURE 27
CAUTION
Bearings can be damaged by drying with
compressed air.

NOTE: Some spigot bearings are two-piece

assemblies. Remove the inner race from the pinion
with a bearing puller. Remove the outer race/roller Corrosion Prevention
assembly from carrier with a drift or a press.
1. Apply gear oil to clean, dry, undamaged parts that
will be reassembled.
2. To store parts, apply a corrosion inhibitor and wrap
CLEANING PARTS them in corrosion inhibiting paper.
Clean all part before inspection and reassembly.
Parts Inspection
Cleaning Ground and Polished Parts Inspect all parts carefully and completely before the
1. Use a cleaning solvent to clean ground or polished axle or carrier is reassembled. Check parts for wear and
parts or surfaces. Kerosene or diesel fuel oil can be damage, repair or replace as required.
used. Do not use gasoline. Follow the solvent 1. Inspect the cup, cone, rollers and cage of all
manufacturer’s instructions for safe use to prevent tapered roller bearings in the assembly. Replace if
injury. any of the following are found:
2. Use a tool with a flat blade if required to remove a. The center of large diameter end of rollers worn
gasket material from parts. Be careful not to level with or below the outer surface;
damage the ground surfaces. b. The radius at large diameter end of rollers worn
3. Do not clean ground or polished parts in a hot to a sharp edge;
solution tank, water, steam or alkaline solutions. c. A visible roller groove in the cup or cone inner
race surfaces. The groove may be seen at the
Cleaning Rough Parts small or large diameter end of both parts;
1. Clean rough parts in the same way as ground and d. Cracks or breaks in the cup, cone inner race or
polished parts. roller surfaces;
2. Rough parts can also be cleaned in hot solution e. Bright wear marks on the outer surface of the
tanks with a weak alkaline solution. roller cage;
3. Parts must remain in hot solution tanks until f. Damage on rollers and on surfaces of the cup
completely cleaned and heated. Follow the and cone inner race surfaces that touch the
manufacturer’s instructions for safe use to prevent rollers;
injury. 2. Inspect hypoid pinions and gears for wear or
4. Parts must be rinsed with water until the alkaline damage. Gears that are worn or damaged must be
solution is removed. replaced.

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CAUTION CAUTION
Hypoid drive pinions and ring gears are Always replace a differential gear nest as a unit.
machined in matched sets. Both the drive gear
and pinion must be replaced at the same time.

4. Inspect axle shafts for wear and cracks at the

3. If the differential was disassembled, inspect the flange, shaft and splines. Replace axle shaft if
following parts (Figures 28 and 29) for wear: required.
a. Both surfaces of all thrust washers;
b. The four trunnion ends of the spider; REPAIRING AND REPLACING FASTENERS
c. Teeth and splines of both differential side gears; All threads in the assembly must be undamaged and
d. Teeth and bore of all differential pinions; clean so that accurate adjustments and correct torque
values can be applied.
e. Inside of case halves.
Ensure that all fasteners and threaded holes are in
good condition:
1. Replace fasteners if the corners of the head are
worn or distorted.
2. Clean and repair fastener threads and holes with a
die or tap of the correct size or a fine file.
3. Replace all damaged washers.
4. When installing new Trio-Loc fasteners, do not
apply adhesives or sealants to the new fastener or
to the hole.
5. When the old fasteners are being reused:
FIGURE 28 a. Clean the oil and dirt from threaded holes. There
is no special cleaning required and it is not
necessary to remove the old Trio-Loc adhesive
from threads.
b. Apply five drops of Rockwell Liquid Adhesive or
Loctite 277 to threaded holes only. Make sure
the adhesive is on the threads.

CAUTION
Do not apply adhesive to the fastener threads.
Air pressure in the hole will push the adhesive
out as the fastener is installed.

INSTALLING FASTENERS
When installing fasteners, torque to the required
FIGURE 29 value for that size fastener (See Torque Chart). Always
use a torque wrench.

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FASTENER REMOVAL
If fasteners are difficult to remove, the strength of the
thread adhesive can be decreased by heating the
fastener for three to five seconds. Repeat as necessary.
Use cleaning solvent with care. Follow the
manufacturer’s instructions to avoid injury.

CAUTION 4. Grind the damaged weld to the base metal.

5. Warm the complete axle housing to a temperature
Do not exceed 350_F (175_C) maximum. of 80_F (27_C) or higher.
Heating must be done slowly to prevent 6. Heat the damaged area to 300_F (150_C) before
thermal stresses in the other components. welding.
7. Use E---7018 or ER---70S---3 welding rod.

REPAIRING PARTS
Remove nicks, mars and burrs from parts having CAUTION
machined or ground surfaces. Use a fine file, India
stone, emery cloth or crocus cloth for this purpose. Ensure that welding rods are dry. Electrodes
not stored in the correct sealed containers
REPAIRING AXLE HOUSING must be heated at 700_F (370_C) for one hour
Certain welded repairs may be made to the axle before welding. Wet electrodes must be dried
housing. Replace a bent or damaged axle housing. at 180_F (82_C) for two hours and then heated
at 700_F (370_C) for one hour before welding.
AXLE WELDING PROCEDURE
8. Fill in the weld gap as follows:

CAUTION
CAUTION
Welding can be used when the crack or
damaged area is within the old weld material.
Ensure that there are no bearings between the
Replace the axle housing if the crack extends
weld area and the ground cable as arcing will
into the metal next to the old weld. A housing
damage the bearing.
that has damage in the seam weld or cover
weld because of overload conditions can be
repaired.
a. The opening in cover welds must be filled level
with the old weld.
b. The opening in seam welds must be ground out
to 70% of the wall thickness. The wall thickness
can be measured at the carrier opening of the
housing.
Failure to follow correct welding procedures c. Clean the new weld area. Carefully remove all
or welding at locations other than the three the rough weld material.
areas allowed will make the heat-treated com- 9. Install the differential carrier and axle shafts.
ponent weak. A weak component will cause 10. Apply a !@8-inch-diameter bead of silicone gasket
poor or unsafe axle operation and early fail-
material.
ure. The following procedure must be used.
NOTE: The following silicone gasket products can be
1. Drain the lubricant from the axle assembly. used: Three bond RTV No. TB 1216, Loctite Ultra Grey
2. Remove the axle shafts and differential carrier from RTV No. 5699.
the axle housing. (See Drive Axle Removal.)
3. Clean the damaged area inside and outside the NOTE: Too much gasket material can block
housing. Cleaning solvent can be used. lubrication passages.

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11. Assemble the components immediately to permit 4. Pinion Cone Variation Number
the silicone gasket material to compress evenly
between the parts. Torque fasteners to NOTE: The pinion cone variation number is not used
specification. (See Torque Chart.) when checking for a matched gear set. The number is
12. Wait 20 minutes before filling the assembly with used when adjusting the depth of the pinion in the
lubricant. carrier. See the procedure for adjusting the shim pack
thickness under the pinion cage in reassembly
CHECKING FOR MATCHED RING GEAR AND procedure later in this section.
DRIVE PINION SET
Before a new gear set is installed in the carrier, check a. Examples of pinion cone variation numbers:
the gear set for correct marks to make sure the gears are PC+3, PC-5, +2, -1, +0.01 mm or -0.02 mm
a matched set (Figure 30). (Figure 31).

FIGURE 30

NOTE: The location of the marks as shown in Figure

30 correspond to the following item numbers.

1. Part Number FIGURE 31

a. Examples of gear set part numbers: Ring gear,
36786; drive pinion, 36787. b. Located on the end of the pinion gear head or
outer diameter of the ring gear.
b. Drive pinion: end at threads.
c. Ring gear: front face or outer diameter. Yoke to Interference Fit Splines Assembly
2. Tooth Combination Number
a. Example of a tooth combination number: 9-41.

NOTE: A 9-41 gear set has a 9-tooth drive pinion and CAUTION
a 41-tooth ring gear.
Ensure that seal lips are clean and free of
b. Drive pinion: end at threads. particles that will cause a leak between the
c. Ring gear: front face or outer diameter. yoke and the seal.
3. Gear Set Match Number
Meritor drive pinion and ring gears are available only
as matched sets. Both gears of a set have a match 1. Apply gear oil on the yoke seal.
number. 2. Check all surfaces of the yoke hub for damage.
a. Example of a gear set match number: M29. 3. Lightly lubricate the yoke journal with gear oil and
partially install the POSE seal onto the yoke 1/4 to
NOTE: A gear set match number has any 1/2 inch (Figure 32).
combination of a number or letter and number.
NOTE: Do not install the POSE seal completely
b. Drive pinion: end of gear end. against the yoke shoulder. This seal will position itself
c. Ring gear: front face or outer diameter. as the yoke is installed.

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FIGURE 32 FIGURE 33
2. Support the bearing cage with metal or wood
blocks.
4. Relubricate the yoke with gear oil. 3. Press the bearing cup into the bore of bearing cage
5. Slide the yoke over the pilot shaft. Align the yoke until the cup is flat against the bottom of the bore.
splines with the shaft splines. Use a sleeve of the correct size to install the bearing
cup (Figure 33).
4. Put the drive pinion in a press, gear head to the
bottom (Figure 34).
CAUTION
Do not use a hammer or mallet to install the
yoke to the input pinion shaft. Using a hammer
or mallet can damage the yoke or flange.

6. Install the input yoke flange onto the drive pinion

shaft. The yoke or flange must fully seat against the
outer differential bearing before the nut is torqued
to specification.
7. Install the drive pinion nut on the input pinion shaft
and against the yoke collar.
8. Torque the nut against the yoke collar to
specification. (See Torque Chart.) FIGURE 34
5. Press the inner bearing cone on the shaft of the
Drive Pinion, Bearings and Bearing Cage drive pinion until the cone is flat against the gear
Assembly head. Use a sleeve of the correct size against the
1. Place the bearing cage in a press (Figure 33). bearing inner race.

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Spigot Bearing Assembly Pinion Bearing Preload Adjustment

1. Put the drive pinion in a press, gear head up (Figure
SPECIFICATIONS
35).
2. Press the spigot bearing on the end of drive pinion New Bearings Used Bearings
until the bearing is flat against the gear head. Use a 5 - 45 lb-in 10 - 30 lb-in
sleeve of the correct size against the bearing inner
(0.57 - 5.0 Nm) (1.2 - 3.3 Nm)
race (Figure 35).
Adjust the pinion bearing preload using one of the
following two procedures.
Press Method
NOTE: If a press is not available, or the press does
not have a pressure gauge, use the flange method to
adjust preload.

1. Put the drive pinion and cage assembly in a press,

gear head toward the bottom.
2. Install a sleeve of the correct size against the inner
race of the outer bearing (Figure 37).

FIGURE 35

3. Install the snap ring into the groove in the end of the
drive pinion with snap ring pliers (Figure 36).

FIGURE 37
3. Apply and hold 54,000 lbs (24,500 kg) pressure to
the pinion bearings. As pressure is applied, rotate
the bearing cage several times so that bearings
make normal contact.
4. While pressure is held against the assembly, wind a
cord around the bearing cage several times.
5. Attach a spring scale to the end of the cord.
6. Pull the scale and cord on a horizontal line. As the
FIGURE 36 bearing cage rotates, read the value indicated on
scale. Make a note of reading (Figure 37).

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7. Measure the diameter of bearing cage where the

cord was wound. Measure in inches (Figure 38).

FIGURE 39

FIGURE 38
CAUTION
8. Divide the diameter in half to get the radius. Make a Do not install tight fit yokes on shafts using a
note of radius dimension. hammer or mallet. A hammer or mallet will
damage the yoke.
9. Calculate the bearing preload torque as follows:
Pounds pulled X Radius (inches) = pound-inches
preload torque. 2. Temporarily install the drive pinion and cage
Example: assembly in the carrier. Do not install shims under
the bearing cage (Figure 40).
Spring scale reading = 7.5 pounds.
Bearing cage radius = 3.31 inches.
7.5 pounds X 3.31 inches = 24.8 lb-in preload.
10. If the preload (torque) of pinion bearings is not
within specifications:
a. To increase preload, install a thinner bearing
spacer.
To decrease preload, install a thicker bearing
spacer.
b. Repeat steps 1 through 9.

Yoke or Flange Method

1. Install the input yoke nut and washer on the drive
pinion. The yoke must be against the outer bearing.
FIGURE 40
NOTE: If the fit between the yoke splines and drive
pinion splines is tight, use a press to install the yoke 3. Install the bearing cage to carrier capscrews.
(Figure 39). If a press is not available, use the Washers are not required at this time. Tighten the
three-piece pilot tool for installation. capscrews hand tight.

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4. Fasten a yoke or flange bar to the input yoke. The NOTE: The preload (torque) of pinion bearings can
bar will hold the drive pinion in position when the nut be increased or decreased slightly by tightening or
is tightened (Figure 41). loosening the pinion nut within specifications.
5. Torque the nut on the drive pinion to 800 - 1100 lb-ft 8. If the preload (torque) of pinion bearings is not
(1090 - 1490 Nm) (Figure 41). within specifications:
a. Remove the pinion and cage from the carrier.
b. To increase preload, install a thinner bearing
spacer.
To decrease preload, install a thicker bearing
spacer.
c. Repeat steps 1 through 7.
After adjusting preload of pinion bearings, remove the
drive pinion and bearing cage from carrier. Follow steps
1 through 4 of the procedure for removing pinion and
cage from carrier.
9. Install a new triple lip seal as follows:
a. Apply bearing grease to the seal lips and cavities
between lips (Figure 43). Ensure that the seal
lips are clean.

FIGURE 41

6. Remove the yoke or flange bar.

7. Attach a torque wrench on the drive pinion nut.
Rotate the drive pinion and read the value indicated
on the torque wrench (Figure 42).

FIGURE 43
b. Apply gear oil to seal bore in bearing cage
(Figure 43).
c. Put the drive pinion and cage assembly in a
press, seal bore toward the top.
d. Press the seal into cover until seal is flat against
the bottom of bore. Use a sleeve or seal driver
that fits against the metal retainer of seal the
diameter of the sleeve or driver. The diameter of
FIGURE 42 the sleeve or seal driver must be larger than the
flange (Figure 44).

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0.015” - 0.030”
(0.38 - 0.76 mm)

FIGURE 44 FIGURE 46

NOTE: If a press is not available, use a brass or PINION CAGE SHIM PACK ADJUSTMENT
leather mallet and the sleeve or driver to install the
NOTE: Use this procedure if a new drive pinion and
seal (Figure 45).
ring gear set is installed, or if the depth of the drive
pinion has to be adjusted (Figure 47).

Follow safe shop practice. Wear eye protection.

Do not hit steel parts with a steel hammer. Parts
or tools can break and cause personal injury.

FIGURE 47

1. Measure the thickness of the old shim pack with a

micrometer (Figure 48). Record the measurement.

NOTE: The pinion cone number can be either

1,000ths of an inch or 100ths of a millimeter. PC+3,
FIGURE 45 PC-3, +3 or -3 equal 0.003 inch. PC+0.03, PC-0.03,
+0.03 or -0.03 equal 0.03 mm. To change millimeters
10. After the triple-lip seal is installed, the gap between to inches, multiply millimeters by 0.03937. To change
the flange and the bearing cage must be 0.015” - inches to millimeters multiply by 25.4.
0.030” (0.38 - 0.76 mm) (Figure 46). Check the gap
with a feeler gauge at several points around the 2. If the old pinion cone number is a plus (+), subtract
seal. The difference between the largest and the number from the old shim pack thickness.
smallest gap measurement must not exceed 0.010” 3. If the old pinion cone number is a minus (---), add the
(0.25 mm). number to the old shim pack thickness.

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NOTE: The value calculated is the thickness of the Examples: Inches mm

standard shim pack, without a variation.
1. Old Shim Pack Thickness +.030 .76
Old PC Number, PC+2 --- .002 ---.05
Standard Shim Pack Thickness .028 .71
4. Look at the pinion cone (“PC”) variation number on
New PC Number, PC+5 +.005 +.13
the new drive pinion that will be installed. Record
New Shim Pack Thickness .033 .84
the number for later use.
2. Old Shim Pack Thickness .030 .76
Old PC Number, PC-2 +.002 +.05
Standard Shim Pack Thickness .032 .81
New PC Number, PC+5 +.005 +.13
New Shim Pack Thickness .037 .94
3. Old Shim Pack Thickness .030 .76
Old PC Number, PC+2 ---.002 ---.05
Standard Shim Pack Thickness .028 .71
New PC Number, PC-5 ---.005 ---.13
New Shim Pack Thickness .023 .58
4. Old Shim Pack Thickness .030 .76
Old PC Number, PC-2 +.002 +.05
Standard Shim Pack Thickness .032 .81
New PC Number, PC-5 ---.005 ---.13
New Shim Pack Thickness .027 .68
Conversion: 1 inch = 24.50 mm; 1 mm = 0.03937 inches

FIGURE 48
CAUTION
5. Look at the pinion cone (“PC”) variation number on Drive pinions and ring gears must be replaced
the old drive pinion that is being replaced. See Gear as matched sets.
Set Information for examples and locations of the
number. Record the number for later use.
8. Install the drive pinion, bearing cage and new shim
6. If the new pinion cone number is positive (+), add pack into the carrier.
the number to the standard shim pack thickness
that was calculated. Drive Pinion, Bearing Cage and Shim Pack
Assembly
7. If the new pinion cone number is negative (---),
subtract the number from the standard shim pack NOTE: If a new drive pinion and ring gear is installed,
thickness that was calculated. or if the depth of the drive pinion has to be adjusted,
calculate the thickness of the shim pack. See Pinion
Cage Pack Adjustment.
NOTE: The value calculated is the thickness of the
new shim pack. See the example in the following 1. Install the correct shim pack between the bearing
chart. cage and carrier (Figure 49).

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4. Align the oil slots in the cover and gasket with the oil
slots in the bearing cage.
5. Install the bearing cage to carrier capscrews and
washers. Tighten capscrews to correct torque
value. See Torque Chart. (Figure 51).

FIGURE 49

2. Align the oil slots in the shims with the oil slots in the
bearing cage and carrier. Using guide studs will
help align the shims (Figure 49).

NOTE: Use a minimum of three shims in a pack. If the FIGURE 51

pack is made from different thickness shims, install
the thinnest shims on both sides of the pack for 6. Install the input yoke nut and washer on the drive
maximum sealing. pinion. The yoke must be against the outer bearing.

3. Install the drive pinion and bearing cage into the

carrier. If necessary, use a rubber, plastic or leather
mallet to tap the assembly into position (Figure 50). CAUTION
Do not install tight fit yokes on shafts using a
hammer or mallet. A hammer or mallet will
damage the yoke.
Follow safe shop practice. Wear eye protection.
Do not hit steel parts with a steel hammer. Parts
or tools can break and cause personal injury. 7. Torque the pinion nut to 800 - 110 lb-ft (1090 - 1490
Nm) (Figure 52).

YOKE
BAR SHOWN

FIGURE 50 FIGURE 52

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8. Install the drive pinion, bearing cage and new shim

pack into the carrier. See the procedure earlier in
this section.

Differential and Ring Gear Assembly

CAUTION
Do not press a cold ring gear on the flange
case half. A cold ring gear will damage the
case half because of the tight fit. Metal
particles between the parts can cause gear
runout that exceeds the 0.008” (0.20 mm) FIGURE 53
Meritor specification. 6. Torque fasteners, see Torque Chart.
7. After the bolts are installed, check for gaps between
the back surface of the ring gear and the case
flange. Use a 0.003 inch (0.076 mm) feeler gauge
1. Expand the ring gear by heating the gear in a tank of and check at four points around the assembly
water to a temperature of 160_ to 180_F (71_ to (Figure 54).
82_C) for 10 to 15 minutes.

Wear protective clothing and gloves when

handling the heated ring gear.

2. Lift the ring gear from the tank of water using a lifting
tool.
3. Install the ring gear on the flange case half
immediately after the gear is heated. If the ring gear
does not fit easily on the case half, heat the gear
again. Repeat step 1.
4. Align fastener holes of the ring gear and flange case FIGURE 54
half. Rotate the ring gear as needed. 8. If the gap is less than 0.003 inch (0.076 mm),
5. Install the bolts, nuts and washers that hold the ring continue with step 9. If the gauge fits more than
gear to the flange case half. Install the bolts from the one-half the distance between the outer diameter of
gear side of the assembly. The bolt heads must be the flange and the pilot diameter of the gear:
against the ring gear (Figure 53). a. Remove the ring gear.

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b. Check the flange case half and ring gear for the 13. Install the spider (cross), differential pinions and
cause of the gap. thrust washers into the flange case half (Figure 57).
c. Repair or replace parts.
d. Assemble the ring gear and flange case half
following steps 1 through 8. CAUTION
9. Install the bearing cones on both case halves. Use a
press and sleeve of the correct size (Figure 55). The side gears in some carrier models have
hubs of different lengths. Install the correct
length side gear into the flange case half.

FIGURE 55

10. Apply gear oil on the inside surfaces of both case FIGURE 57
halves, the spider, the thrust washers, the side
gears and differential pinions.
14. Install the second side gear and thrust washer
11. Put the flange case half on a bench, ring gear teeth over the spider and differential pinions (Figure 58).
toward top.
12. Install one thrust washer and side gear into the
flange case half (Figure 56).

FIGURE 58

15. Put the plain half of the differential case over the
flange half and gears. Rotate the plain half as
FIGURE 56 needed to align the match marks (Figures 58 and
59).

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a. Install soft metal covers over vise jaws to protect

the ring gear (Figure 61).

FIGURE 59

16. Install Trio-Loc fasteners into the case halves. See

Fastener Repair and Replacement and the FIGURE 61
following:
a. Install four capscrews and washers or bolts, nuts
and washers into the case halves. The distance
between the fasteners must be equal. Tighten
the fasteners to the correct torque value in a
pattern opposite each other (Figure 60). See
Torque Chart.

15

FIGURE 62
b. Put the differential and ring gear assembly in the
vise.
c. Install the tool into the differential until the splines
of the tool and one side gear are engaged
(Figure 61).
d. Attach a torque wrench to the nut of the tool and
FIGURE 60
rotate the differential gears. As the differential
b. Install the other fasteners into the case halves. gears rotate, read the value indicated on the
Torque the fasteners, see the Torque Chart. torque wrench (Figure 62).
17. The rotating resistance of the differential gears e. If the torque value exceeds the specification,
cannot exceed 50 lb-ft (68 Nm) torque applied to disassemble the differential gears from the case
one side gear. halves and check the case halves, spider, gears
and thrust washers for the cause of the high
NOTE: Make a tool for checking the rotating torque value. Repair or replace parts as
resistance of the differential gears. The tool can be necessary.
made from an axle shaft that matches the spline size f. After the parts are assembled, retest the rolling
of the differential side gear (Figure 61). resistance torque.

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DIFFERENTIAL GEAR SET INSTALLATION 4. Install the bearing cups over the bearing cones that
1. Clean and dry the bearing cups and bores of the are assembled on the case halves (Figure 64).
carrier legs and bearing caps.
2. Apply gear oil on the inner diameter of the bearing
cups and on both bearing cones that are
assembled on the case halves.
3. Apply Meritor adhesive in the bearing bores of the
carrier legs and bearing caps as follows:

NOTE: Meritor adhesive hardens in approximately

two hours. The following two steps must be
completed within two hours of the adhesive’s
application. If two hours have passed, clean the parts
and reapply adhesive.

a. Clean oil and dirt from outer diameters of

bearing cups and bearing bores in the carrier
and bearing caps. There is no special cleaning
FIGURE 64
required.
b. Apply gear oil to the bearing cones and the inner 5. Lift the differential and ring gear assembly and
diameters of the bearing cups of the main install into the carrier. The bearing cups must be flat
differential. Do not get oil on the outer diameter against the bore between the carrier legs (Figure
of the bearing cup and do not permit oil to drip 64).
on the bearing bores. 6. Install both of the bearing adjusting rings into
c. Apply a single continuous bead of the adhesive position between the carrier legs. Turn each
to the bearing bores in the carrier and bearing adjusting ring hand tight against the bearing cup
caps. Apply the adhesive around the smooth, (Figure 65).
ground surfaces only. Do not put adhesive on
threaded areas (Figure 63).

FIGURE 65
7. Install the bearing caps over the bearings and
adjusting rings in the correct locations as marked
FIGURE 63
before removal (Figure 66).

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NOTE: Do not install the cotter keys, pins or lock

plates that hold the bearing adjusting rings in
position. Continue by adjusting the preload of
differential bearings, adjust backlash of the hypoid
gear and check tooth contact patterns.

Differential Bearings Preload Adjustment

Specification: Differential bearing preload torque ---
15 - 35 in-lbs.
1. Attach a dial indicator on the mounting flange of the
carrier.
2. Adjust the dial indicator so that the plunger or
pointer is against the back surface of the ring gear
FIGURE 66 (Figure 67).

Follow safe shop practice. Wear eye

protection. Do not hit steel parts with a
steel hammer. Steel parts and tools can
break causing serious injury.

8. Tap each bearing cap into position with a light

leather, plastic or rubber mallet. The caps must fit
easily against the bearings, adjusting rings and
carrier. Do not force the bearing caps into position.

FIGURE 67
CAUTION
If bearing caps are not installed in correct 3. Loosen the bearing adjusting ring that is opposite
locations, the bores and threads in caps will the ring gear so that a small amount of end play
not match the carrier. Problems assembling shows on the dial indicator (Figure 68 and 69).
the caps on the carrier and damage to parts
can occur. Do not force the bearing caps into
position.

CAUTION
9. If bearing caps do not fit correctly into position,
check the alignment of match marks between caps When turning the adjusting rings, always use a
tool that engages two or more opposite
and carrier. Remove the caps and repeat steps 6
notches in the ring. A “T” bar wrench can be
through 8. used for this purpose. If the tool does not
10. Install the capscrews and washers that fasten correctly fit into the notches, damage to the
bearing caps to the carrier. Tighten the capscrews lugs will occur (Figure 68).
by hand, then torque the capscrews to the correct
torque value. See Torque Chart.

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FIGURE 68 FIGURE 70

5. Tighten the same bearing adjusting ring until no end

play shows on the dial indicator.
6. Tighten both bearing adjusting rings one more
notch.
4. Move the differential and ring gear to the left and
right with pry bars while reading the dial indicator. 7. Continue by checking runout of the ring gear.
Use one of the following methods, a or b. Ring Gear Runout
a. Use two pry bars that fit between the bearing 1. Attach a dial indicator on the mounting flange of the
adjusting rings and ends of the differential case. carrier (Figure 71).
The pry bars must not touch the differential
bearings (Figure 69).

FIGURE 71

2. Position the dial indicator so that the pointer is

against the back of the ring gear (Figure 71).
3. Rotate the differential and ring gear while reading
FIGURE 69 the dial indicator. The total runout must not exceed
0.008 inch (0.20 mm).
4. If ring gear runout exceeds specifications:
b. Use two pry bars between the differential case or a. Disassemble the differential and ring gear.
ring gear and the carrier at locations other than b. Check the differential parts including the carrier
described in step a. The pry bars must not touch for the cause of the runout.
the differential bearings (Figure 70). c. Repair or replace parts.

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d. Install the differential and ring gear into the

carrier.
e. Repeat preload adjustment of differential
bearings.
Ring Gear Backlash Adjustment
Measure the outer diameter of ring gear for
approximate pitch diameter (Figure 72).

FIGURE 73
2. Adjust the dial indicator so that the plunger or
pointer is against the tooth surface (Figure 73).
3. Adjust the dial of the indicator to zero.
4. Hold the drive pinion in position.
5. While reading the dial indicator, rotate the
differential and ring gear a small amount in both
FIGURE 72
directions, against teeth of the drive pinion. If the
Specifications: Used gear backlash range --- 0.008 to backlash reading is within specification, continue
0.018 inch (0.20 to 0.45 mm); new gear backlash --- by checking tooth contact patterns. If the backlash
0.012 inch (0.30 mm). reading is not within specifications, adjust backlash
If the old gear set is installed, adjust the backlash to as needed. Continue by following steps 6 and 7.
the setting measured before the carrier was NOTE: Backlash is increased by moving the ring gear
disassembled. away from the drive pinion (Figure 74).
If a new gear set is installed, adjust the backlash to the
specification for new gear sets.
TIGHTEN ADJUSTING RING THIS SIDE
While checking the tooth contact patterns, adjust the
backlash to specified limits, if necessary, to change the
location of the pattern.
1. Attach a dial indicator on the mounting flange of the
carrier (Figure 73).

LOOSEN ADJUSTING RING THIS SIDE

FIGURE 74
NOTE: Backlash is decreased by moving the ring
gear toward the drive pinion (Figure 75).

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LOOSEN ADJUSTING RING THIS SIDE

TIGHTEN ADJUSTING RING THIS SIDE

FIGURE 75 DRIVE SIDE

(CONVEX)

6. Loosen one bearing adjusting ring one notch, then

FIGURE 77
tighten the opposite ring the same amount (see
Figures 74 and 75).

NOTE: When adjusting backlash, move the ring gear Tooth Contact Patterns Of Conventional Hypoid
only. Do not move the drive pinion. Gear Sets
1. Adjust the backlash of a new gear set to 0.012 inch
(0.30 mm). Adjust the backlash of an old gear set to
7. Repeat steps 2 through 6 until the backlash is within
the setting that was measured before the carrier
specifications.
was disassembled. See Ring Gear Backlash
Adjustment.
Gear Set Tooth Contact
2. Apply a marking compound, such as oiled red lead,
The carrier has a hypoid gear set. In the following to approximately 12 gear teeth of the ring gear.
procedures, movement of the contact pattern in the Rotate the ring gear so that the 12 gear teeth are
length of the tooth is indicated as toward the “heel” or next to the drive pinion (Figure 78).
“toe” of the ring gear (Figure 76).

FIGURE 78
FIGURE 76
3. Rotate ring gear forward and backward so that the
12 gear teeth go past the drive pinion six times to
Always check tooth contact patterns on the drive side get the contact patterns. Repeat if needed to get a
of the gear teeth (Figure 77). clearer pattern.

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4. Look at the contact patterns on the ring gear teeth. For new gear sets, the location of good hand-rolled
Compare the patterns to Figures 79, 80 and 81. tooth contact patterns will be toward the toe of the gear
tooth and in the center between the top and bottom of
the tooth (see Figure 79).
When the carrier is being operated, a good pattern
will extend approximately the full length of the gear tooth.
The top of the pattern will be near the top of the gear
tooth (see Figure 82).

GOOD HAND-ROLLED
PATTERN

FIGURE 79

GOOD OPERATING PATTERN

FIGURE 82

The location of a good hand-rolled contact pattern for

an old gear set must match the wear pattern in the ring
gear. A hand-rolled pattern will be smaller in area than
the wear pattern.
If the contact patterns require adjustment, continue
by following step 5 to move the contact patterns
HIGH PATTERN
between the top and bottom of the gear teeth. If the
contact patterns are in the center of the gear teeth,
continue by following step 6.
FIGURE 80 5. Change the thickness of the shim pack under
bearing cage to move the contact patterns between
the top and bottom of the gear teeth. Use the
following procedure.

NOTE: A high contact pattern indicates that the drive

pinion was not installed deep enough into the carrier.
A low contact pattern indicates that the drive pinion
was installed too deep in the carrier.

a. Remove the drive pinion and bearing cage from

the carrier. (See Drive Pinion and Bearing
Cage Removal).
b. To correct a high contact pattern, decrease the
thickness of the shim pack under the bearing
LOW PATTERN cage (Figure 83).
c. To correct a low contact pattern, increase the
FIGURE 81 thickness of shim pack under the bearing cage
(Figure 83).

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MOVE PATTERN TOWARD TOE

LOOSEN ADJUSTING RING THIS SIDE

TIGHTEN ADJUSTING RING THIS SIDE

DECREASE INCREASE
SHIM PACK SHIM PACK MOVE PATTERN TOWARD HEEL

TIGHTEN ADJUSTING RING THIS SIDE

HIGH CONTACT PATTERN LOW CONTACT PATTERN

CORRECTION CORRECTION
LOOSEN ADJUSTING RING THIS SIDE
FIGURE 83
d. Install the drive pinion, bearing cage and shims
into the carrier. See the procedure on previous
pages. FIGURE 84
e. Repeat steps 2 through 5 until the contact c. Repeat steps 2 through 4 and 6 until the contact
patterns are in the center between the top and patterns are at the correct location in the length
bottom of the gear teeth. of the gear teeth.
6. Adjust backlash of the ring gear within specification 7. Install the cotter keys between lugs of the adjusting
range to move the contact patterns to the correct ring and through the boss of the bearing cap. Bend
location in the length of the gear teeth. See the the two ends of the cotter key around the boss
previous procedure. (Figure 85).
a. Decrease backlash to move the contact patterns
toward the toe of the ring gear teeth (Figure 84).
b. Increase backlash to move the contact patterns
toward the heel of the ring gear teeth (Figure 84).

FIGURE 85

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Thrust Screw Installation and Adjustment

Specification: Thrust screw to ring gear clearance
0.025 to 0.045 inch (0.64 to 1.14 mm) or 1/2 turn of the
thrust screw.
1. Install the jamnut on the thrust screw, one half the
distance between both ends.
2. Install the thrust screw into the carrier until the screw
stops against the ring gear (Figure 86).

FIGURE 88

Differential Carrier Installation

Use cleaning solvent with care. Follow the

manufacturer’s instructions to avoid injury.
FIGURE 86
1. Clean the inside of axle housing and the mounting
surface. Use a cleaning solvent and rags to remove
3. Back off the thrust screw !@2 turn (180 degrees) dirt. Blow dry the cleaned areas with air. Also see
(Figure 87). the procedure on cleaning axle assembly earlier in
this section.
2. Inspect the axle housing for damage. Repair or
replace the axle housing. See the procedure earlier
in this section.
3. Check for loose studs in the mounting surface of the
housing where the carrier fastens. Remove and
clean the studs that are loose.
4. Apply liquid adhesive to the threaded holes and
install the studs into axle housing. See the
procedure outlined earlier. Tighten studs to current
torque value. See Torque Chart.
5. Install the carrier into the axle housing. Use a
hydraulic roller jack or a lifting tool.

FIGURE 87
Ensure proper shop ventilation. Small amounts
of acid vapor are released as silicone gasket
4. While holding the thrust screw in position, tighten material cures. Follow the manufacturer’s
the jamnut to the correct torque value against the instructions.
carrier (Figure 88). See Torque Chart.

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6. Apply a !@8-inch-diameter continuous bead of the

silicone gasket material around one surface. Also
apply the gasket material around the edge of all
fastener holes in that surface (Figure 89).

CAUTION
Apply a 1/8-inch-diameter bead of silicone FIGURE 90
gasket material. Too much gasket material can
block lubrication galleries.
10. Repeat step 9 until the fasteners are properly
torqued. See Torque Chart.
11. Install the other fasteners and washers that hold
the carrier in the axle housing. Tighten fasteners to
the correct torque value. See Torque Chart.

NOTE: Wait 20 minutes before filling the assembly

with lubricant.

12. Install the axle shafts and gaskets into the axle
housing and carrier. The gasket and flange of the
axle shafts must fit flat against the wheel hub
(Figure 91).

FIGURE 89

NOTE: The following silicone gasket products can be

used: Three bond RTV No. TB 1216, Loctite Ultra Grey
RTV No. 5699. FIGURE 91

13. Install the capscrews and washers that hold the

axle shaft to the wheel hub. Tighten capscrews to
7. Carefully push the carrier into position.
the correct torque value. See Torque Chart.
8. Install nuts and washers or capscrews and washers 14. If the wheel hubs have studs, install the tapered
in the four corner locations around the carrier and dowels at each stud and into the flange of the axle
axle housing (Figure 90). shaft. Use a punch or drift and hammer if needed.
9. Tighten the four fasteners two or three turns each, in 15. Install the nuts and washers on the studs. Tighten
an opposing pattern. nuts to the correct torque value. See Torque Chart.

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FIGURE 92

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TORQUE CHART

FASTENER THREAD SIZE TORQUE VALUE TORQUE VALUE

lb-ft N⋅m
2 Nut, Axle Shaft Stud Plain Nut 0.625 - 18 150 - 230 203 - 311
Lock Nut 0.625 - 18 130 - 190 177 - 257
3 Breather 0.375 - 18 20 - 27 27 - 36
4 Plug, Oil Filler (Housing) 0.750 - 14 35 - 47 48 - 63
5 Plug, Heat Indicator 0.50 - 14 25 - 34 34 - 46
6 Plug, Oil Drain 0.750 - 14 25 - 34 34 - 46
7 Capscrew, Differential Case 0.38 - 16 35 - 50 48 - 68
0.44 - 14 60 - 75 81 - 102
0.50 - 13 85 - 115 115 - 156
0.56 - 12 130 - 165 176 - 224
0.62 - 11 180 - 230 244 - 312
M12 x 1.75 85 - 96 116 - 130
M16 x 2 203 - 251 275 - 340
8 Nut, Differential Case Bolt 0.50 - 13 75 - 100 102 - 136
0.50 - 20 85 - 115 115 - 156
0.62 - 11 150 - 190 203 - 258
0.62 - 18 180 - 230 244 - 312
M12 x 1.75 74 - 96 100 - 130
9 Nut, Ring Gear Bolt 0.50 - 13 75 - 100 102 - 136
0.50 - 20 85 - 115 115 - 156
0.62 - 11 150 - 190 203 - 258
0.62 - 18 180 - 230 244 - 312
M12 x 1.25 66 - 81 90 - 110
M12 x 1.75 77 - 85 104 - 115
M16 x 1.5 192 - 214 260 - 290
10 Capscrew, Bearing Cap 0.56 - 12 110 - 145 149 - 197
0.62 - 11 150 - 190 203 - 258
0.75 - 10 270 - 350 366 - 475
0.88 - 14 360 - 470 488 - 637
0.88 - 9 425 - 550 576 - 746
M16 x 2 181 - 221 245 - 300
M20 x 2.5 347 - 431 470 - 585
M22 x 2.5 479 - 597 650 - 810
12 Capscrew, Carrier to Housing 0.625 - 11 150 - 230 203 - 311
0.625 - 18 150 - 230 203 - 311
13 Jam Nut, Thrust Screw 0.75 - 16 150 - 190 203 - 258
0.88 - 14 150 - 300 203 - 407
1.12 - 16 150 - 190 203 - 258
M22 x 1.5 148 - 210 200 - 285
M30 x 1.5 236 - 295 320 - 400
14 Nut, Drive Pinion M45 x 1.5 996 - 1232 1350 - 1670
15 Capscrew, Bearing Cage 0.38 - 16 30 - 50 41 - 68
0.44 - 14 50 - 75 68 - 102
0.50 - 13 75 - 115 102 - 156
0.56 - 12 110 - 165 149 - 224
0.62 - 11 150 - 230 203 - 312
M12 x 1.75 74 - 96 100 - 130

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SERVICE TOOLS
SOME OF THE TOOLS USED FOR THE MAINTENANCE PROCEDURES OUTLINED
IN THIS SECTION ARE NONSTANDARD. THEY ARE, HOWEVER, AVAILABLE FOR
PURCHASE FROM MCI SERVICE PARTS. WHERE PRACTICAL, THEY MAY BE
FABRICATED AT THE SERVICE FACILITY.

20-- 143 SHAFT

20-- 144 COLLAR

20-- 145 NUT

20-- 142 TOOL KIT -- YOKE INSTALLATION 6256

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NOTE: Carrier stand, part no. J-3409-D,

is available from Kent-Moore, Heavy
Duty Division.

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SPECIFICATIONS
DRIVE AXLE ASSEMBLY
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Meritor
Wheel Track (Center of Dual Wheels) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76.6” (1945 mm)
Gear Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hypoid
Axle Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pressed Steel Housing
Drive Axle Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.30:1
Drive Axle Lube Capacity (approximate) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Qts. (20 liters)

CLEARANCE
Differential Bearing End Play . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.000” (0.00 mm)
Differential Gear Run-Out Max. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.008” (0.20 mm)
Hypoid Gear Backlash (New Gear Sets) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.012” (0.30 mm)
Hypoid Gear Backlash Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.008” --- 0.018” (0.20 --- 0.45 mm)

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SECTION 2B

TAG AXLE
Maintenance information for the tag axle varies little from the front axle. This
section has been combined with Section 1, Front Axle. Please refer to Section 1 for
information on the tag axle.

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SECTION 2C

ALIGNMENT PROCEDURE
(FOR HUNTER SERIES 111 BUS & TRUCK ALIGNMENT SYSTEMS)

CONTENTS OF THIS SECTION

SUBJECT PAGE
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2C-3
Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2C-3
Pre-Alignment Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2C-3
Inspection of Aligning Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2C-3
Vehicle Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2C-3
Alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2C-4
Alignment Specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2C-4
Adjustment and Compensation of Wheel Sensors . . . . . . . . . . . . . . . . 2C-5
Drive Axle Alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2C-6
Front Axle Alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2C-6
Tag Axle Alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2C-7
V-Link Centering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2C-8

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Wheel Adapter Spindle

Wheel Adapter

Turn Plate

FIGURE 1. TYPICAL SET-UP

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GENERAL DESCRIPTION and attach it to the idler and front axle steering arm.
Make sure there is sufficient engagement of the ball
This section contains the alignment procedure using joint threads exceeding the specified minimum.
the Hunter Series 111 Truck and Bus Alignment Exposed thread max. 1.62 inches (41.15 mm),
Systems. torque ball joint nuts to 150 ft-lbs., and clamp nuts
to 60 ft-lbs.
PROCEDURE B. INSPECTION OF ALIGNING EQUIPMENT
A. PRE-ALIGNMENT PROCEDURES 1. Check the date of the last calibration on the
1. Use centering shims to adjust the upper alignment equipment. It should be no older than
suspension links to ensure all axles are centered one month.
with respect to the body as outlined in Appendix A 2. Turn the aligning equipment on and warm it up.
below. 3. Check all wheel sensors and wheel adapters for
2. Index the Pitman arm to the mark on the bottom of damage and for loose components (Figure 1).
the steering gear sector shaft, turn nut on, and 4. Inspect all toe lines. Make sure they are not frayed
torque to 405 ft-lbs. Using a punch and a hammer, and/or have poor elasticity. Replace them if
deform the collar of the sector shaft nut into the necessary.
groove provided in the shaft.
5. Verify that all four sensors are fully mounted on
3. At the middle of the steering gear range, align the wheel adapter spindles.
mark on the input shaft of the steering gear so it
6. Inspect turn plates for binding or restricted travel
points over the center of the body of the steering
(Figure 1).
gear.
4. Ensuring that the steering gear remains in a C. VEHICLE PREPARATION
straight-ahead position, attach the telescoping 1. Move vehicle into alignment audit area and relax
steering shaft to the input shaft while the steering suspension by slowly moving vehicle forward and
wheel is in the straight-ahead position. Ensure the back approximately 10 feet in a straight line three
universal joint split is oriented towards the curbside (3) times.
of the vehicle. 2. Position vehicle with front and tag axle wheels
5. Adjust the length of the drag link to approximately centered on turn plates.
49 inches between the center of the ball joints, and 3. Put the transmission in neutral and apply the
attach it to the longer arm of the Pitman arm and to parking brake.
the longer arm of the steering idler on the front axle. 4. Chock the drive axle in fore and aft directions.
Make sure there is sufficient engagement of the ball
5. Record tire pressures and correct if required.
joint threads exceeding the specified minimum.
Exposed thread max. 41.5 mm (1.62 inches), 6. Check and adjust the air suspension to ensure
torque ball joint nuts to 150 ft-lbs., and clamp nuts coach is at ride height.
to 60 ft-lbs. 7. Record vehicle’s mileage.
6. Adjust the length of the intermediate drag link to 8. Check kingpin and bearing for excessive play (not
35.82 inches between the center of the ball joints required for new coaches).

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ALIGNMENT SPECIFICATION
All listed parameters must be measured and recorded.
Left Total Right Nominal Notes
Font Axle Min. Max. Min. Max. Min. Max.
Camber - 0.187 0.687 - 0.187 0.687 0.25
(degrees)
Caster 1.50 3.50 1.50 3.50 3.00 Coach at
(degrees) ride height
Individual 0.015 0.046 0.015 0.046 Unloaded
Toe (in.) Max. Diff.
0.1
Total Toe 0.031 0.093 0.062 Loaded
(in.) 0.031
Set Back - 0.060 0.060
(degrees)
Cross caster max. 0.5 degree front and tag axles
Drive Axle
Thrust - 0.060 0.060
Angle
(degrees)
Tag Axle
Camber - 0.187 0.687 - 0.187 0.687 0.25
(degrees)
Caster 2.00 3.50 2.00 3.50 3.00 Coach at
(degrees) ride height
Individual 0.015 0.046 0.015 0.046 Unloaded
Toe (in.) max. Diff.
0.1
Total Toe 0.031 0.093 0.062 Loaded
(in.) 0.031

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D. ALIGNMENT (ALL DATA EXCLUSIVELY REFER TO HUNTER SERIES 111 EQUIPMENT)

ADJUSTMENT AND COMPENSATION OF WHEEL centering indicated by noticeable movement in
SENSORS (HUNTER SERIES III EQUIPMENT) the wheel sensor.
Select ”total 4 wheel” alignment type and ”truck/bus d. At the time of the front sensor mounting, rotate
type 2” of the vehicle. wheels clockwise to get wheel adapters 180
1. Reset aligner. Enter vehicle specifications and tire degrees from upright with green LED lighted.
diameter. e. Slide the sensor on the wheel clamp rods to align
a. Press R twice. the sensor lock knob with the center of the wheel
b. Press K4 - Begin Alignment. hub. Approximate centering is adequate for the
rear sensors. This is applicable to older
c. Press K4 - Select vehicle manufacturer, ”Enter
systems, only new wheel sensors have a
Manufacturer”.
self-centering mounting system.
d. Press K4 - Select vehicle model/axle, ”Enter
Model”. 4. Lift the front axle.
e. Press K3 - Enter toe reference diameter, ”Enter 5. Install the front wheel sensors as outlined under
Number”. step 3 above.
f. Press K4 - Continue. 6. Mount the rear wheel sensors onto the drive axle as
outlined under step 3 above.
g. Press K4 - Select vehicle type, ”Enter”.
7. Compensate each wheel sensor for wheel run out,
h. Press K4 - Select front axle configuration,
one at a time. During compensation of one wheel,
”Enter”.
do not allow the other wheel to be moved or rotated.
i. Press K4 - Select rear axle configuration, Enter to Remember to rotate the wheels in the same
’1 drive axle with trailing axle’, ”Enter”. direction each time - clockwise.
j. Press K4 - Select TOTAL alignment procedure, a. With the adapter upside down, rotate the wheel
”Enter”. until the light comes on, then tighten the sensor
2. Alignment Machine lock knob.
a. Press shift three times. b. Rotate the wheel until the sensor spirit bubble is
b. Press K2 - enter coach customer. level.
c. Enter down to vehicle make. c. Activate the compensation switch, and wait for
d. Enter down to license (use CA or CB and unit #). the flashing red light.
e. Enter down to technician (enter clock #). d. Release the sensor lock knob.
f. Press K4 to continue. e. Rotate the wheel approximately 180 degrees
3. Installation procedure for the wheel sensors. until the green light is constantly on, then tighten
the sensor lock knob.
a. Rotate the wheels to get tire valve stem in a
position between 1 and 5 o’clock. Install the f. Rotate the wheel until the sensor spirit bubble is
wheel sensors with the knob at 12 o’clock level.
position and install the safety cables. Be certain g. Activate the compensation switch, and wait for
that the wheel mounting is secure and seated the constant red light. Do not loosen the sensor
firmly on the rim lip or O.D. of the aluminum lock knob.
wheels. 8. Lower the front axle tires onto the turn plates with
b. Mount the rear wheel sensors with the wheel the wheel clamps right side up.
clamp assemblies right side up. Be certain that 9. Raise the drive axle and release the park brake if
the wheel mounting is secure and seated firmly necessary.
on the steel rim lip or on the O.D. of the aluminum
wheels. 10. Compensate each rear sensor as per step 7 above.
c. Center the sensor assembly by sliding the 11. With the wheel clamp right side up, lower the drive
sensor casting on the wheel clamp rods to align axle and apply the park brake.
the sensor lock knob with the center of the wheel 12. Re-level all four sensors, without loosening the
hub. This is required on older equipment only. sensor lock knobs, by using moderate hand
Hunter K111 and P111 have a self-centering pressure, and rotating the sensor on its shaft until
wheel sensor mounting system. Always rotate the spirit bubble is centered. Loosen the sensor
the wheel clockwise to check for incorrect lock knobs only if necessary to rotate it by hand.

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DRIVE AXLE ALIGNMENT FRONT AXLE ALIGNMENT

1. During the alignment process, no measurements 1. Access the STEER AHEAD screen.
should be taken until the sensors are leveled and
2. Steer the front wheels to center the STEER AHEAD
locked.
cursor - equalize the toe values. Check the steering
2. Install the longitudinal toe lines between the front gear to ensure that the indexing mark for straight
and rear sensors and tension them tight enough to ahead is in the same position as it was when
eliminate excessive toe line sagging. Ensure installed. If the steering gear is not positioned in the
tensioning springs are partially extended at all straight-ahead position, correct its position and
times. lock it in place. Loosen the clamps on the
3. Measurement of the FRAME OFFSET ANGLE is intermediate drag link and turn the drag link tube to
required to be entered into the alignment split the toe-in on the front wheels again. Torque the
equipment to reference the angle of the vehicle clamps.
frame with respect to the sensor centerline. The 3. Check the front sensor spirit levels and re-center the
sensor centerline is the bisector of the angle formed spirit level bubbles as required.
by the left and right longitudinal toe lines
determined by the position of wheel sensors. This 4. Measure front axle setback and record it. The front
line is not the same as a line joining the midpoints of axle setback is the angle between the centerline
the two axles. and a perpendicular to the front axle.

To obtain the Frame Offset Angle, measure the 5. Record and document the vehicle’s initial alignment
lateral distance, using a tape measure, from the measurements.
alignment strings to a selected hard point on the 6. Access the CASTER STEER screen.
body at the front and drive axles, followed by a
7. Apply and hold the service brake.
longitudinal measurement between these points on
one side. At the front and at the rear, select 8. Turn the front wheels to achieve the turn angle
reference points on the body as close to the wheel required by the computer for locking in to check the
sensors as practical. For each axle, the reference caster on the front wheels. The front axle wheel
points on each side of the vehicle should be caster angles are measured with respect to the
identically located with respect to the vehicle drive axle thrust line.
centerline. Add the obtained values to the FRAME 9. Release the service brake.
OFFSET MEASUREMENTS screen.
10. Shim the radius rods to bring the computer
4. Access the STEER AHEAD screen. readings within tolerance. Shim the radius rods at
5. Split the front axle individual toe by steering the front the axle end to increase the caster and shim at the
wheels to center the STEER AHEAD cursor. body side to decrease the caster. For torque values
Equalize the LH and RH toe values. This ensures see Section 12. Steer to measure the caster, steer
that the front axle wheels are pointing in the same axle inclination (SAI), and included angle according
direction as the drive axle. Do not be concerned to the cursors. Do not over steer cursors.
with the value of TOTAL TOE.
11. Verify that the camber is within specifications listed
The FRONT AXLE INDIVIDUAL TOE is measured in the Alignment Specifications table.
with respect to the DRIVE AXLE THRUST LINE. The
12. Set the front axle toe-in to axle specifications listed
drive axle thrust line is the bisector of the total rear
in the Alignment Specification table by loosening tie
toe angle and determines the vehicle’s
rod clamps on the front axle, and then turning the tie
straight-ahead direction.
rod to adjust toe-in. For torque values refer to
6. Check the front sensor spirit levels and re-center Sections 1, 2 and 12.
spirit level bubbles as required.
13. Split the toe after adjustments are made and check
7. Check the initial thrust angle of the drive axle, and the steering gear to ensure that the indexing mark
shim the radius rods on the axle end to adjust as per for straight ahead is in the same position as it was
specification. (For torque values see Section 12.) when installed. If the steering gear is not positioned
Jack up the drive axle during the thrust angle in the straight-ahead position, correct its position
adjustment to relieve any stresses in the and lock it in place. Loosen the clamps on the
suspension. intermediate drag link and turn the drag link tube to
The drive axle thrust angle is the angle between split the toe on the front wheels again. Torque the
drive axle thrust line and the sensor centerline. clamps (see A.6).

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14. Set the steering gear stops by turning past the Note: The computer reverses all readings therefore
power steering assisted turns of the steering gear the operator doesn’t have to reverse any of the
until the axle stops are contacted. Make sure the readings.
wheels can be turned 51˚, measured on the inner
wheels, in both directions. 2. Lift the tag axle.
15. Record and document the vehicle’s alignment 3. Lower the wheel sensors to allow the lateral
angles after total toe has been corrected. transducers attached at the end of extension arms
of the wheel sensors to measure across the vehicle,
16. Adjust the main drag link length. Ensure the wheels then compensate each sensor as per step D.7.
are in a straight-ahead position by equalizing the
4. Lower the tag axle tires onto the turn plates with the
toe. Drag link length is determined by positioning
wheel clamps right side up.
the Pitman arm according to the steering gear
indexing - see marks on the steering gear. This may 5. Raise the drive axle and release the park brake if
only be done after centering and aligning the front necessary.
axle (see A.5). 6. Compensate each rear sensor as per step D.7.
17. Hit the K4 button on the computer to save the 7. With the wheel clamp right side up, lower the drive
existing settings (do not reset the computer or turn axle and apply the park brake.
the bus around). 8. Re-level all four sensors, without loosening the
sensor lock knobs, by using moderate hand
TAG AXLE ALIGNMENT pressure, and rotating the sensor on its shaft until
1. To start the alignment of the tag axle move the the spirit bubble is centered. Loosen the four bolts
sensors to the following locations, and mount them that attach the middle plate to the tie rod.
as per D.3. All sensors must face rear. 9. Verify that the camber is within specifications listed.
a. Sensor from the right front axle wheel to the left 10. Ensure the tag axle wheels are in a straight-ahead
tag axle wheel. position by equalizing the individual toe measured
b. Sensor from the left front axle wheel to the right with respect to the drive axle thrust line. Equalize
tag axle wheel. the individual toe values by shimming the radius
rods on the axle end first (or on both ends, if
c. Sensor from the right drive axle wheel to the left required) to adjust as per specification. For torque
drive axle wheel. values, see Section 12. Jack up the tag axle during
d. Sensor from the left drive axle wheel to the right this adjustment to relieve any stresses in the
drive axle wheel. suspension.

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V---LINK CENTERING b. Insert the amount of shim previously calculated

1. Set the coach in high ride mode, apply the park between the body and the V-link bar pin (Figure
brake and shut the engine off. 2).
2. Turn the main battery disconnect switch to OFF. c. Re-tighten the fasteners and torque to 340 ft. lbs.
3. Block all wheels. d. Re-bend the lock strap around the flats of the
fastener head as shown in Figure 2.
4. Place stands underneath the rear legs of the front
and the rear bogie. 13. Jack up the axle to a height which allows the V-link
apex to engage in the suspension support structure
5. Depressurize the air suspension system by pulling
mount and position the V-link in the mount.
the drain valve on all four auxiliary suspension
reservoirs. 14. Install the fasteners connecting the V-link apex to
the suspension support structure and torque to
Note: The following steps 6 through 14 have to be 420 ft. lbs.
performed on all axles affected, beginning with the
front axle. NOTE: After performing the above procedure, it is
necessary to realign the vehicle at a capable
6. Jack up the axle to a height where the V-link is alignment shop.
horizontal to the ground.
7. Remove and retain the fasteners connecting the
V-link to the suspension support structure.
8. Remove the V-link from the suspension support Coach Body

structure and allow it to hang freely while lowering V-Link Bar Pin

the axle back to the ground.

9. Using a tape measure, determine the horizontal
distance between the bogie beam and the tip of the
V-link apex bushing bar pin on one side, using an
accurate straight edge where required. Record this
Install shim in this position
value as “Dimension X” (see Figure 2).
10. Measure the opposite side of the V-link apex
bushing bar pin and record this value as Lock Strap

“Dimension Y” (see Figure 2).

11. Do the following calculation to determine the
required thickness of the shim: (X --- Y) / 2 = Z . The FIGURE 2. Typical Installation Location
value “Z” defines the thickness of the shim required of V-Link Shim
at the arm end of the V-link corresponding to the
side with the shorter dimension measured.

Example: Curb side of axle - “Dimension X” between X Y

bogie and V-link bar pin is 18.875 in.

Road side of axle - “Dimension Y” between bogie and Inside Face of Bogie
V-link bar pin is 18.625 in. Beam

Calculation: (18.875 in. --- 18.625 in.) / 2 = 0.125 in.

Calculation indicates that a 0.125 in. shim is required
at the road side V-link arm end.
V-Link Bar Pin V-Link Apex

12. If required, install the shim(s)at the affected V-link

arm end as follows: Curbside Roadside
a. On the side requiring shimming only, carefully
unbend the fastener lock strap and loosen the
fasteners attaching the V-link arm end to the FIGURE 3. Measuring Points
coach body. Do not remove the fasteners.

MOTOR COACH INDUSTRIES

Printed in Canada.
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 Date March 2003

SECTION 3
BODY
A -- Structure and Exterior Components
B -- Interior Components
C -- Doors
D -- Windows
E -- Lifting
F -- Towing

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 3A-1

SECTION 3A

STRUCTURE & EXTERIOR COMPONENTS

CONTENTS OF THIS SECTION

SUBJECT PAGE
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A-2
Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A-2
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A-3
Exterior Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A-3
New Finishes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A-3
Routine Washing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A-3
Vinyl Graphics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A-4
Lucite SAR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A-4
Corrosion Prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A-4
Exterior Body Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A-5
Understructure Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A-5
Understructure Corrosion Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A-6
Structural Welding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A-6
Panel Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A-6
Fiberglass Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A-6
Surface Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A-7
Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A-7
Aluminum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A-7
Fiberglass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A-7
Painting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A-8
Prime Painting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A-8
Finish Painting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A-9
Decal Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A-9
Exterior Mirrors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A-9
Drip Moldings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A-11
Fenders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A-11
Mud Flaps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A-11
Bumpers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A-11
Service Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A-12
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A-14

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 3A-2

GENERAL DESCRIPTION Exterior Panels

Figure 2 shows the sidewall construction.
The frame is made of stainless steel tubing, sheet and
plate. Suspension-bearing members are high-strength,
low alloy, low corrosion steel. Exterior panels are
aluminum or fiberglass-reinforced plastic. Drip moldings
are paintable aluminum.
Fixed fiberglass panels are attached with adhesives
and stainless steel rivets. Removable fiberglass panels
are attached with corrosion-resistant fasteners. There
are no exposed panel fasteners. Suspension and bogie
structures are coated with epoxy paint. Dissimilar metals
are separated by mastic or Mylar tape.

COMPONENTS
Frame
FIGURE 2
Two welded steel structures form the substructure at
the front and drive axles and provide the base for the air The front roof cap is a one-piece fiberglass panel,
suspension. Fiberglass or aluminum bulkheads extending from the B-post to the top of the front bumper.
separate the baggage compartments, fuel tank, It has recessed housings for lights.
batteries and heating and air conditioning equipment. The rear roof cap is a fiberglass panel, extending from
Steel ferry skids are welded to the substructure at the the rear passenger windows to the top of the rear
front and rear of the coach. bumper. It has recessed housings for lights and the
lavatory and cross-seat windows. The rear roof cap has
Center Tunnel provisions for installing a back-up camera.
The center tunnel runs under the aisle. It contains The main roof panel is a single sheet, high-tensile
tubing and wiring harnesses, and has heating and air primed aluminum panel. It is installed with stainless steel
conditioning ducts on both sides (Figure 1). rivets and urethane structural adhesive.
The one-piece panel below the side windows is
fiberglass bonded within stainless steel channels.
CAUTION The panels below the floor line are made of
fiberglass-reinforced plastic.
Do not drill holes in the aisle floor. The har- Exterior Coatings
nesses and tubing run close to the floorboard,
Aluminum is factory-coated with a baked-on epoxy
and could be damaged. This area is 15 inches
(38 cm) wide for the length of the coach. finish. After fabrication, a final coat of DuPont Imron
epoxy polyurethane enamel paint is applied and oven
baked.
NOTE: The base exterior finish color is gloss white.
The roof and other areas not specified on the paint
chart remain gloss white.
Front tire and rear engine compartment panels are
painted gloss grey with DuPont Centari acrylic enamel.
Front and rear bogie assemblies are finished in gloss
black. Trim around glass is semi-gloss black.
Drip Moldings
High-tensile aluminum drip moldings extend along
CENTER TUNNEL both sides of the coach above the window line.
Rub Rails
Painted, injection molded plastic rub rails extend
FIGURE 1 along the length of the baggage doors.

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 3A-3

Fenders Routine Washing

The fenders are removable, one-piece, molded Wash and rinse water must be free of solids.
resilient polymer. Recirculating systems must function satisfactorily with
Lucite windows.
Mud Flaps
The splash guards are rubber with inserted polyester Detergents
rubber. Use a solvent-based dissolving detergent with the
prewash spray and a highly-lubricating detergent with
Bumpers the brushes. Follow the detergent manufacturers’
The three-piece bumpers are made of energy- recommendations. The water and detergent mixture
absorbing, paintable, injection molded plastic. should be 90_-110_F.
Paintable molded corner bumperettes are mounted If the detergent does not contain sequestering
with rubber washers at the rear of the vehicle. agents, soften water to four grains hardness or less.
A recessed area in the front bumper houses two fog Follow the manufacturer’s recommendations.
lamps and provision for two licence plates. The release Use a high-pressure water spray prewash to remove
lever for the bumper is in the left front service grit before brushing. Detergent may be used with the
compartment. prewash.
Exterior Mirrors Install a small extra spray arm to cover the window
The mirror heads attach by setscrews to the pivoting area only. Put this arm 5 - 7 feet (1.5 - 2.1 m) from the
support arms. The support arms mount to the bracket prewash spray so that its effect is not diluted.
with capscrews. The brackets mount to the LH/RH Brushes
A-posts with screws. The mirrors have replaceable Tampico-fibered brushes are recommended. Do not
convex and flat glass sections. use brush filaments that have a high wax content.
Polypropylene is satisfactory and may be flagged for
MAINTENANCE optimum performance.

EXTERIOR CLEANING 1
Wash the coach exterior regularly. Do not use alkaline 25---40 Ft.
(7.6---12.2M)
cleaners on aluminum, iron or steel. Do not use abrasive
cleaners, polish or steel wool; they remove the Detergent High Brush Final
Prewash Pressure Rinse
protective coatings and can scratch and discolor the Water
Lubricating
finish. Do not wax. Prewash
Spray

New Finishes 2
A new finish cures for 30 to 60 days, depending on
5---7’ 25---40 Ft.
temperature. Hand wash only. (7.6---12.2M)

High Brush Final

CAUTION Pressure
Water
Detergent
Prewash Lubricating
Spray
Rinse

Prewash

Do NOT use high-pressure washers during 3

the curing period. Damage to the paint sur-
face can result. 25---40 Ft.
(7.6---12.2M)

High Pressure Brush Final

1. During the curing period, wash by hand only. Clean Detergent Lubricating Rinse
Prewash Spray
frequently using clean water rinses. If the coach
exterior is extremely dirty, use a mild, neutral PH,
non-abrasive detergent and clean water. WASHING EQUIPMENT SCHEMATIC 2638
2. DO NOT use high-pressure washers until the paint
has cured and hardened. FIGURE 3

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 3A-4

We recommend a round filament. Filament suppliers Household cleaners that have been tested and found
sell round filament on request. effective in cleaning Lucite SAR include Easy-Off,
Brush pressure and the amount of filament that Windex, Glass Plus, Top Job, Mr. Clean and Fantastik.
contacts the coach are the two factors most damaging Industrial cleaners effective on acrylic windows are
to Lucite SAR windows and painted surfaces. The Neleco Subway Soil Solvent (Neleco Products, Inc.) and
pressure should be as low as possible, and no more C-1102 Alkaline Cleaner (DuBois Chemicals).
than six inches of filament may overlap the coach side as To remove paint, ink marks and graffiti that is resistant
the brush turns. to household cleaners, use a soft cloth saturated with
The coach should travel through the prewash, wash isopropanol or an aliphatic hydrocarbon solvent. Do not
and rinse at 1 - 2 mph (1.6 - 3.2 kph). Never stop the use abrasive cleaners. Do not use razor blades or other
coach while it is in contact with the brushes. sharp instruments that might gouge the surface.
Two commercially-available antistatic cleaners that
Rinse Cycle effectively clean Lucite SAR windows and reduce static
The final rinse should be a high pressure, high volume build-up are Like-Magic Type N1-5 and Trend Antistat
rinse with a minimum delivery of 125 gpm (473 Cleaner. Follow the manufacturers’ instructions when
L/minute). using antistatic cleaners.
Vinyl Graphic
After graphics have been applied, wait one week CORROSION PREVENTION
before washing. This ensures the adhesives bond. Road splash causes moisture, dirt and road salt to
accumulate in crevices and on flanges, causing
After the first week, wash, ensuring the following:
corrosion. The coach’s operating environment
1. Use only mild cleaning solutions. Do not use determines its risk for corrosion. Corrosion can be
solvents or abrasive cleaners. controlled by preventative maintenance.
2. If using high-pressure equipment, do not exceed 1. Wash the coach frequently, as determined by
1200 psi. operating conditions.
3. Do not exceed 120_F (50_C) water temperature. 2. Wash daily when the coach is exposed to road salt.
4. Maintain a minimum distance of 12” (30 cm) from 3. Regularly inspect for corrosion. Inspect high-risk
the nozzle to the decal surface. areas more frequently.
5. Keep nozzle perpendicular to the decal surface. 4. Before and after the winter, thoroughly inspect the
6. Do not scrub. body and understructure for corrosion.
7. Test cleaning agents and methods prior to use to
determine their suitability. CAUTION
8. Neither highly acidic (less than pH 3), nor highly
alkaline (greater than pH 11).
Failure to properly maintain the coach’s body
9. Free of strong aromatic solvents chlorinated surfaces and structural components affects
solvents and ketone. the coach warranty.
Cleaning Lucite SAR
Use conventional techniques to clean Lucite SAR. Inspection
However, take care to use a clean, soft (unsized) cloth.
Wet the window surface with the cleaning solution NOTE: For detailed cleaning, painting, removal and
before wiping. When oily surface contamination is installation information, see the specific procedures
present, the cleaning solution may not wet the surface in this section.
thoroughly until it is rubbed with the cloth.
1. Wash the coach body, undercarriage and cavities to
NOTE: Minimize filament contact with Lucite SAR remove all dirt and salt.
during brush wash to guard against scratches. 2. Inspect the exterior body and undercarriage for
Provide a soft roller or wheel guide on the brush arm signs of corrosion or bare metal. Pay particular
to prevent brush over-pressure. attention to the following areas:

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 3A-5

Exterior Body Inspection

1. Remove the bumpers. Clean, remove corrosion
and paint as required.
2. Open all baggage and service doors. Remove dirt
and inspect sealant between sidewall panels and
lower body panels for decay or cracks. Apply
Sikaflex as required.
3. Inspect the entrance door and moldings. Clean,
remove corrosion and paint as required.
4. Remove the fenders (Figure 4). Clean, remove
corrosion, paint as required.

FIGURE 5

2. Baggage floor: Inspect all fasteners and seams. As

required, fill seams, remove corrosion, prime, paint
and undercoat.
3. Rear bogie area (Figure 6): Clean and inspect
flanges, seams, bulkheads, the bogie, air lines and
components, electrical harnesses, connectors and
fasteners. Remove corrosion, repair, prime, paint,
undercoat as required. Replace corroded
components, lines, connectors and fasteners.

FIGURE 4

5. Inspect all panels, seams and fasteners. Clean,

remove corrosion and paint as required.
6. Inspect window frames and moldings. Clean and
paint as required.
7. Inspect the drip moldings, roof caps and panel
seams. Check for loose rivets, replace as required.

Understructure Inspection
1. Front bogie area (Figure 5): Clean and inspect
flanges, seams, bulkheads, the bogie, air lines and
components, electrical harnesses, connectors and
fasteners. Remove corrosion and repair, prime,
paint, undercoat as required. Replace corroded
components, lines, connectors and fasteners. FIGURE 6

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 3A-6

Understructure Corrosion Repair 2. Remove and sand the panel in the marked areas to
Any damaged paint, undercoating or corrosion must roughen the mounting surfaces. Apply Dolphinite
be repaired immediately as follows: sealer to the channel mounting surface and the
1. Remove dirt, grease and oil in accordance with sanded area of the fiberglass panel. Position and
Surface Preparation. clamp the panels in place with any necessary
shims. Inspect the panel for proper fit.
2. Remove corrosion and loose coating with a wire
3. Drill holes through the panel from the underside of
brush or by sandblasting.
the channel. Existing holes in the roof bow channel
may be used as a template.
CAUTION NOTE: Drill only 4 or 5 holes at one time. Do not drill all
the holes and then rivet. Before riveting, ensure
Bulkheads, brackets and other structural correct alignment.
members may be sandblasted. Do not
sandblast exterior side paneling. Do not FIBERGLASS REPAIR
sandblast excessively. Fiberglass repairs generally consist of reinforcing
cracked or broken areas. Large holes, torn sections and
separated joints require a laid-up cloth and resin repair.
Allow the repair to harden and then finish. Repair small
WARNING depressions, scratches or pits with body putty.

Follow safe shop practices. Wear hearing WARNING

protection, a face shield, gloves, protective
clothing and respiration equipment.
Use rubber gloves and wear a mask when
working with resins. Some people
experience a skin reaction to resins. If this
3. After removing all corrosion, review the extent of the happens, wipe the skin with denatured
damage, repair, prime, paint as required. alcohol or clean thinner. Protective hand
creams are available; their use is
STRUCTURAL WELDING recommended.

NOTE: Refer to the welding caution in the Use a respirator and wear goggles when
grinding or sanding.
Introduction section of this manual before starting
any welding operation. All welding must conform to Some resin dust is combustible. Use a low
D1.1 of the AWS Structural Steel Welding speed, air-driven disc sander with a water
Specification. attachment or a dry sander with a vacuum
bag attachment.
The exterior shell framework components, including
truss frames, are manufactured from T304 stainless The following tools and materials may be required:
steel. Major suspension bearing members are made of 1. hacksaw blade,
high strength, low alloy steel. 2. assorted files,
3. emery paper or cloth (No. 150 grit or finer),
PANEL REPLACEMENT
4. scissors or tin snips,
Panel replacement generally requires removal of
5. wax paper or cellophane sheets,
rivets, screws or capscrews.
6. small 3-inch (76 mm) grooved roller,
When replacing the roof panel or front lower cap, fit
the new panel to the old panel and mark the rivet 7. paint brush,
locations on the underside. 8. putty knife,
1. If the roof bow channels are bent or damaged, alter 9. acetone and
or replace them to match the contours of the 10. one or more heat lamps.
fiberglass panel. Some areas may require shims. The ambient temperature should be 70_ to 75_F (21_
Mark the location and thickness for each shim. to 24_C) when making fiberglass repairs.

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Printed in Canada.
 Date March 2003 Page 3A-7

SURFACE PREPARATION 3. Apply 224S Conversion Coating: In a plastic

container and without dilution, use an abrasive pad
The following surface preparations cover bare and
and apply to the treated metal surface. Leave the
painted metal and fiberglass.
coating on the surface for 2 to 5 minutes. Work only
Carbon and Corten Steel as much area as you can coat and rinse before the
1. Surface Preparation: Wash with 3812S Enamel solution dries. Reapply the coating if the surface
Reducer and wipe the surface dry with a clean dries before rinsing.
cloth. 4. Rinse: Flush the surface with cold water or mop it
2. Apply 5717S Metal Conditioner: In a plastic with a damp sponge or cloth rinsed occasionally in
container, mix 5717S metal conditioner with two clean water. Wipe the surface dry with clean cloths
parts water. Apply to the surface with a cloth or or allow it to air dry.
sponge; if corrosion is present, use an abrasive 5. Apply 825S Corlar Epoxy Primer.
pad. Wipe the surface dry with clean cloths.
3. Apply 224S Conversion Coating: In a plastic Aluminum
container and without dilution, use an abrasive pad 1. Surface Preparation: Wash with 3812S enamel
and apply the coating to the treated metal surface. reducer and wipe the surface dry with clean cloths.
Leave it on the surface for 2 to 5 minutes. Work only 2. Apply 225S Aluminum Cleaner: In a plastic
as much area as you can coat and rinse before the container, mix 225S aluminum cleaner with two
solution dries. Reapply the coating if the surface parts water. Apply to the surface with a cloth or
dries before rinsing. sponge; if corrosion is present, use an abrasive
4. Rinse: Flush the surface with cold water or mop it pad. Wipe the surface dry with clean cloths.
with a damp sponge or cloth rinsed occasionally in 3. Apply 226S Conversion Coating: In a plastic
clean water. Wipe the surface dry with clean cloths container and without dilution, use an abrasive pad
or allow to air dry. and apply the coating to the treated metal surface.
5. Apply 825S Corlar Epoxy Primer. Leave it on the surface for 2 to 5 minutes. Work only
as much area as you can coat and rinse before the
NOTE: Allow heavy components to come to room solution dries. Reapply the coating if the surface
temperature before painting. Condensation inhibits dries before rinsing.
paint adhesion. 4. Rinse: Flush the surface with cold water or mop it
with a damp sponge or cloth rinsed occasionally in
Stainless Steel clean water. Wipe dry with clean cloths or air dry.
1. Surface Preparation: Wash with 3812S enamel 5. Apply 824S/825S Epoxy Primer.
reducer. Wipe dry with clean cloths. Fine particle
sandblast or sand well. Fiberglass
2. Apply 5717S Metal Conditioner: In a plastic 1. Surface Preparation: Wash the surface with 3819S
container, mix 5717S metal conditioner with two PrepSol. While it is still wet, wipe dry with a clean
parts water. Apply to the surface with a cloth or cloth.
sponge; if corrosion is present, use an abrasive 2. Sand the surface thoroughly, clean it and apply
pad. Wipe the surface dry with clean cloths. 824S/825S Corlar Epoxy Primer.

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 3A-8

PAINT COMPONENTS Prime Painting (Bare Surface)

Coaches are painted with Dupont Imron paint. This 825S Corlar Epoxy Primer (red) is recommended for
paint is two-part (pigmented base and activator) epoxy prime coating bare steel, stainless steel and aluminum
high-gloss polyurethane enamel. Companion products surfaces. 824S Corlar Primer (gray) is recommended for
include an optional dry time accelerator, an additive to bare fiberglass and aluminum.
eliminate fisheyes and reducer. ACTIVATION - to two parts 824S/825S primer add one
ACTIVATOR - Imron must be activated with 192S part 826S activator.
Activator. Ratio: 1 part 192S activator to three parts INDUCTION PERIOD - allow activated primer to stand
Imron. Mix thoroughly. one hour at 70_F (21_C) and above; two hours when
temperature is below 70_F (21_C). This allows the
ADDITIVES - 189S Dry-Time Accelerator - to be used for
chemical reaction to take place.
faster tape-free time. Ratio: up to four ounces of 189S to
one gallon of mixed Imron. POT LIFE - three days at 70_F (21_C).
FISH EYE ELIMINATOR - when necessary, use 259S to REDUCTION - reduce activated primer 33% by volume
eliminate fish eyes. Use up to two ounces per gallon. (ratio 3:1) with 3602S lacquer thinner, or to a viscosity of
21 to 24 seconds in a Dupont M-50 viscosity cup or
REDUCERS - 8485S is used to reduce Imron to a equivalent.
viscosity of 18 to 22 seconds in a Dupont M-50 viscosity
APPLICATION - using 45 - 55 psi at the gun, spray one
cup. 8100S is used as an Imron retarder.
full wet coat to give a dry film thickness of 0.7 - 1.0 mils.
NOTE: Clean all equipment with 3602S Lacquer DRYING TIME - 2 to 6 hours, depending on temperature
Thinner or 8485S Reducer immediately after use. and thickness. Overnight drying may be necessary
when two or three coats have been applied or when
temperatures are low.
AIR PRESSURE - 50 psi at the gun for solid colors; 65
psi at the gun for metallic colors. Prime Painting (Previously-Coated Surface)
1. Wash painted surfaces with soap and water to
remove dirt and water-soluble contaminants.

WARNING 2. Wipe the painted surfaces with 3919S Prep-Sol to

remove wax, grease and other contaminants. While
the solvent is wet, wipe the surface dry.
Use care when storing, handling, mixing and 3. Repair flaws in the painted surface by grinding off
applying paints and chemicals. Topcoat, paint in the damaged areas and filling with body
primer, solvent, accelerators, activators and filler, as required. Featheredge ground-off areas by
cleaners are highly volatile and toxic. machine or hand sanding. Treat bare metal areas
Observe all manufacturers’ instructions and with the appropriate conditions and conversion
the following: coatings.
1. No smoking in the paint room or adjacent 4. Apply 824S, 825S, 100S or 110S.
areas. 825S Corlar Epoxy Primer (red) is recommended for
2. Use only NIOSH-approved respirators. priming or spot priming previously-painted steel,
3. Adequate ventilation must be maintained. stainless steel or aluminum. 824S Corlar Epoxy Primer
(gray) is recommended for priming or spot priming
4. Wash hands before eating. previously painted fiberglass or aluminum.
5. Wear rubber gloves, rubber apron and ACTIVATION - to two parts 824S/825S primer add one
face shield during all phases of paint and part 826S activator.
chemical handling.
INDUCTION PERIOD - allow activated primer to stand
6. If available, use operator-supplied air one hour at 70_F (21_C) and above; two hours when
(Independent Breathing Apparatus). temperature is below 70_F (21_C). This allows the
chemical reaction to take place.
POT LIFE - three days at 70_F (21_C).
PAINT APPLICATION REDUCTION - for spot repairs, reduce the activated
primer 20% by volume (ratio 5:1) with 3602S lacquer
NOTE: Follow the manufacturer’s instructions. thinner.

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APPLICATION - using 45 - 55 psi at the gun, spray until 2. After sanding, wipe the surface with DuPont T-3812
satisfactory filling is achieved (2 to 4 coats). solvent. This solvent does not affect the rubber or
DRYING TIME - 4 to 8 hours. Overnight drying may be interfere with paint adhesion.
necessary. 3. Apply DuPont Imron paint directly to the prepared
100S Gray/110S Red Oxide Multi-Purpose Acrylic surface. Use the activation and reduction
Lacquer Primer may be used as an alternate priming recommended in Paint Components.
system for making spot repairs on small bare metal
areas. Treat metals as described above. DECAL APPLICATION
REDUCTION - 80 - 125% by volume (ratio 1:1) to a Observe the following drying times to prevent
viscosity of 23 to 24 seconds on a Dupont M-50 viscosity blistering when applying decals over Imron paint:
cup or equivalent with 3661S lacquer thinner in the the Overnight drying following:
mid-temperature ranges and 3602S lacquer thinner S 30 minutes drying at 180_F (82_C),
during warm weather. S 60 minutes drying at 140_F (60_C), or
APPLICATION - using 35 - 45 psi at the gun, spray three S 120 minutes drying at 110_F (43_C).
or more coats as needed. Allow each coat to completely
flash. EXTERIOR MIRRORS
DRYING TIME - allow paint to dry thoroughly before Exterior mirrors have three major components: the
sanding (30 to 60 minutes). mounting bracket, mirror arm and mirror head. (Figure
7) The mirror head has a flat mirror and a convex mirror.
Finish Painting (Metal Surface) Both mirrors are adjustable from the driver’s
On non-metallic solid colors, spray a medium first compartment. Mirrors are heated by a thermostat
coat. Allow it to become tacky and spray a full second controlled heating element in the glass. the heater
coat. activates at temperatures below 45_F (7_C). Mirror
For metallic colors, spray three light-to-medium controls are shown in Figure 7.
coats. After hiding has been achieved, reduce activated
Imron 15% with 8485S Imron reducer. Apply one or two Major Adjustments
mist coats to improve flow out and reduce mottling. The mirror arm and head position is manually
Two-tone paint schemes can be done in 6 to 10 hours, adjustable:
if temperatures are at 77_F (25_C) with no more than 1. Loosen the mounting bolts and set screws.
50% humidity. Using 189S accelerator reduces the time 2. Adjust the mirror position.
to 2 to 4 hours at 70_ - 75_F (21_ - 24_C).
3. Tighten the mounting bolts and set screws. Torque
Finish Painting (Rubber Surface) mounting bolts to 25 lb-ft (34 Nm).
Exterior rubber parts may be painted or repainted
using the procedures listed below. Glass Replacement
Mirror glass is held in place by Velcro. To replace:
1. If the item is new, prepare the surface by sanding
with #320 paper. If the item was previously painted, 1. Switch battery disconnect OFF.
remove old paint by sanding only; DO NOT use 2. Gently pry the damaged glass off the backing plate.
paint removing solvents. They will cause rubber 3. Unplug the heater wire connectors. This may
deterioration and impair paint adhesion. require backing plate removal.
NOTE: Never use alcohol or solvents containing 4. Plug in the new mirror glass heater wire connectors.
alcohol on rubber. Alcohol attacks rubber and causes 5. Position the glass on the backing plate and apply
poor paint adhesion. even pressure to properly fasten the Velcro.

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FLAT
MIRROR

WIRE LEAD
MIRROR FOR HEATED MIRROR
HEAD

CONVEX
MIRROR
BALL STEM

BALL CUP
HALF
CENTERLINE
MIRROR ARM OF ARM

MOUNTING
BRACKET
SET SCREW

POSITION BALL CUP

HALVES SO THE JOINT
BETWEEN THEM LIES ON
THE CENTERLINE OF THE
MOUNTING ARM. ENSURE THAT THE
BOLT SET SCREWS ARE NOT ON
THE JOINT BETWEEN THE
CUP HALVES.

MIRROR
REMOTE
CONTROL

MIRROR
HEAT
SWITCH

FIGURE 7

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DRIP MOLDINGS MUD FLAPS

The drip moldings are retained by screws and Standard single black rubber mud flaps are installed
two-sided tape. Drip moldings may be removed for at front and rear locations. A single mud flap may also be
replacement or to gain access to the roof panel. installed between the drive and trailing axles.

Drip Molding Removal Mud Flap Removal

1. Turn the battery disconnect switch OFF.
1. Turn the battery disconnect switch to OFF.
2. Remove mounting hardware retaining the rubber
2. Remove all fasteners holding the end caps and
flaps and metal strip.
molding in place.
3. Remove the flap.
3. Gently remove the molding from the roof panels.
4. Clean the tape from the drip moldings. BUMPERS
Front Bumper Removal
Drip Molding Installation
1. Turn the battery disconnect switch OFF.
1. Apply two-sided tape to the backs of the drip
molding sections. 2. Release the bumper latch and allow it to swing open
and lock. Position blocks to support the bumper
2. Apply sealant at fastener locations. when it is unfastened.
3. Install the moldings. 3. Release spring tension, and remove the spring
retaining pins. Remove the latch assembly.
NOTE: Use P/N 19-1-1356 screws if the holes are
4. Remove the two hinge pins.
stripped.
Front Bumper Installation
1. Install in the reverse order of Removal. Adjust
FENDERS spring tension and shim the bumper as necessary.
Fenders can be removed for replacement. The single
Rear Bumper Removal
front and dual rear fenders are installed as basic. The
1. Turn the battery disconnect switch OFF.
rear fenders have a side turn lamp assembly installed.
2. Remove the top cover panel. Position blocks to
Fender Removal support the bumper when it is unfastened.
1. Turn the battery disconnect switch OFF. 3. Unfasten the two spigots.
2. Disconnect the turn lamp from the fender assembly. Rear Bumper Installation
3. Remove the fasteners from inside the wheel well’s 1. Install in the reverse order of Removal. Shim as
retaining strips. necessary.

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SERVICE TOOLS
SOME OF THE TOOLS USED FOR THE MAINTENANCE PROCEDURES IN THIS
SECTION ARE NONSTANDARD. THEY ARE AVAILABLE FOR PURCHASE
FROM MOTOR COACH INDUSTRIES SERVICE PARTS. WHERE PRACTICAL,
THEY MAY BE FABRICATED AT THE SERVICE FACILITY.

HAND RIVET GUN (AVDEL NO. 165) Bucking or Squeezing

20 --- 171: (C/W tip for 1/4-inch Monobolt Rivets)

2711

POWER RIVETER (GH743) 20---160 20 --- 7: Buck Riveting Tool Kit --- for brazier head,
universal head, round head and flat head rivets of
aluminum, steel or copper.
Consists of:
1. Rivet Bucking Foot
2. 5/32” Brazier Head
3. CP---4444 ”A” Pneumatic Hammer Pistol Grip
4. 7/32” Brazier Head
5. Bucking Dolly Tool Holder

2698

20 --- 10: Panel Clamping Kit --- Consists of:

1. Wedge Lock Clamp 1/4-inch used to hold
panels in place.
2. Wedge Lock Pliers for applying Clamp.
(also available, lighter duty No. GH703 not shown) The following tools are required when replacing
20 --- 170: Nosepiece --- 1/4” Monobolt Rivet Stainless Steel Semi-Tubular Rivets.
20 --- 161: Pulling Head --- 3/16” Cherry ”N” & Cherry CP---4444A Pneumatic Hammer Pistol Grip.
”Q” Rivets

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20 --- 129: CP---4444A Rivet Gun Cupped Squeezer

Set
1/ inch Long (6.35 mm)
4-
20 --- 130: CP---4444A Rivet Gun Cupped Squeezer Set
3/ inch Long (9.52 mm)
8-
2699

20 --- 125: CP---4444A Rivet Gun Drive Set

3 1/2 inches Long (88.9 mm)
20 --- 126: CP---444A Rivet Gun Tool Drive Set
5 1/2 inches Long (139.7 mm)

2703

03-27-1050: Lacing Tool, 9/16-inch Eye

DUAL-COMPONENT DISPENSE TOOL

2700

20---127: CP---444A Rivet Gun Flaring Squeezer Set

1/ inch Long (6.35 mm)
4-
20 --- 128:CP---4444A Rivet Gun Flaring Squeezer Set
3/ inch Long (9.52 mm)
8-

2701

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SPECIFICATIONS
EXTERIOR MIRROR ASSEMBLY
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ramco
FRONT BUMPER ASSEMBLY
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Regal
REAR BUMPER ASSEMBLY
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Regal

FILLER METALS

APPLICATION DIAMETER A.W.S

SS to SS or Corten, Light Gauge #/32 Inch (2.4 mm) No. 308
SS to SS or Corten, Heavy Gauge !/8 - %/32 Inch (3.2 - 4.0 mm) No. 308
Corten to Corten, Light Gauge #/32 - !/8 Inch (2.4 - 3.2 mm) No. 6011
Corten to Corten, Heavy Gauge #/32 - %/32 Inch (2.4 - 4.0 mm) No. 7018
Air Beam Reservoirs, Heavy Plate Sections %/32 Inch (4.0 mm) No. 7018

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SECTION 3B

INTERIOR COMPONENTS
CONTENTS OF THIS SECTION

SUBJECT PAGE
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3B-2
Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3B-2
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3B-2
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3B-3
Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3B-3
Driver’s Seat and Seat Belt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3B-3
Destination Sign . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3B-3
Floor Covering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3B-3
Lubrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3B-3
Parcel Rack Hinges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3B-3
Cleaning Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3B-3
Upholstery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3B-3
Floor Covering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3B-4
Cleaning Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3B-4
Service Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3B-4
Floor Covering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3B-4
Driver’s Seat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3B-5
Destination Sign . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3B-5
Service Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3B-8
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3B-8

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GENERAL DESCRIPTION stainless steel track welded to the floor frame. Floor
tracks are flush to the top of the floor covering.
COMPONENTS Drivers’ Seats
Any of four driver’s seat models may be installed:
Parcel Racks National Seating 93-B with swivel, National Seating 93-B
Overhead parcel racks are located on both sides of without swivel, Isringhausen 6800, and USSC 9100ALX.
the coach above the passenger seats. Doors are hinged The National Seating models are mechanical seats. The
and have a latch at the bottom center. Isringhausen and USSC models are air-ride seats.
Passenger service modules are mounted on the Armrests and seat belts are provided on all models.
underside of the parcel racks. There is one module for
each double passenger seat. Modules contains reading
Destination Sign (Optional)
lights with switches, call switches and passenger The removeable destination sign is located in the
controlled air outlets. window above the windshield. The upper and lower idler
rollers are nylon. The destination sign is driven by an
Fluorescent lighting is provided at the window side electric motor and activated by a rocker switch on the
and aisle side of the parcel racks. In-station lights are back of the sign. (Figure 1).
available. They can be switched between the aisle side
only or the aisle and window side combined. The fixtures
are 24-volt, fed from coach power or from a 110-volt
converter.

Interior Panels
The ceiling at the extreme front and the rear window
area is fiberglass-reinforced plastic. The main ceiling
area is Xorel FR over ABS. The sidewall panels below the
windows have a fabric cover.
SWITCH
Floor
The floor is 1/2”-thick (13 mm) good-one-side fir VIEWER
plywood. The floor is attached to the underframe with
urethane adhesive and rivets. The floor covering is FIGURE 1
heavy-duty rubber or, optionally, non-slip vinyl.
OPERATION
The driver’s floor and front entrance area are at the
same level. The passenger area is 6” higher, achieved by Driver’s Seat
an 8-foot-long (2.4 m) welded ramp that runs between The driver’s seat can be adjusted forward and back,
the first two rows of passenger seats. the seat cushion can be tilted up or down, and the seat
can be raised or lowered. Seat controls are located at the
Passenger Seats front-left on National Seating Model 93B seats. Seat
Passenger seats are lightweight with foam-padded controls are located at the front-right on Isringhausen
backs and cushions. Armrests are provided at the wall 6800 and USSC 9100ALX seats. For more information
and aisle sides. The seats are fastened with tee-bolts in a see the Operator’s Manual.

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MAINTENANCE CLEANING METHODS

INSPECTION Upholstery Dry Cleaning

Covers that are removed for cleaning should be dry
Driver’s Seat and Seat Belt Inspection cleaned to avoid shrinkage. Other than spot cleaning,
Inspect monthly: dry cleaning covers while they are in place is not
1. Ensure that the driver’s seat adjusts and that all recommended.
adjustments lock into place.
2. Inspect the seat belt. Replace if cut or frayed.
3. Ensure that the belt is clean. If necessary, wipe with WARNING
mild soap and warm water. Do not use solvents,
bleach or dye.
Solvent fumes can be harmful. Open
4. Inspect retractors for wear or damage. windows and doors.
5. Ensure smooth operation. If reel is sluggish, fully
extend the belt and spray the reel lightly with
aerosol lubricant. Replace retractors that jam. Upholstery Shampoo
6. Ensure that seat belt mounting is tight. Use either a commercial foam upholstery cleaner or
make a foam cleaner by mixing mild detergent with
water, and working it into a thick foam.
WARNING 1. Gently beat upholstery to raise dirt.
2. Vacuum upholstery.
Replace seat belts that are frayed, cut or 3. Remove stains.
damaged, or were in use during accident.
4. Working in small areas, apply foam using a brush,
sponge or clean cloth. Avoid soaking. Rub.
Destination Sign Inspection 5. Sponge suds from the fabric with a clean, damp
1. Ensure that mechanism moves freely. sponge or cloth. Rinse the sponge or cloth often
2. Inspect for loose wires, clips, hanging tape. Repair with clean water.
or remove as necessary.
6. Allow upholstery to dry. Moisture may be blown off
3. Inspect the inside of the sign compartment. with compressed air, but first blow out and test the
Remove dirt and foreign objects. Clean the inside of line to ensure that it does not contain oil.
the compartment.
NOTE: The destination sign has nylon gears; no
Upholstery Stain Removal
lubrication is necessary. Prompt attention will remove most stains on fabric
upholstery, but improper treatment can increase
damage. If in doubt, seek expert advise. Do not use
Floor Covering Inspection soap, washing powder, ammonia, soda or bleach.
Inspect the flooring at least once a year: These products may damage the dye or fabric. Two stain
1. Inspect the floor covering for damage. removal methods are:
2. Ensure that welds and seals are intact. Method 1: Open windows and doors to ventilate.
3. Ensure that flooring is watertight. Apply nonflammable dry cleaning solvent with a clean,
white, absorbent cloth. Treat small areas, working from
LUBRICATION the other edge toward the center of the stain. Blot
Parcel Rack Hinges frequently with a dry, clean cloth.
Regularly lubricate parcel rack door hinges with a Method 2: Sponge the stain with detergent and
light application of aerosol lubricant, light engine oil or lukewarm water solution. Do not soak. Rub with a damp
Vaseline. cloth, rinsing the cloth frequently.

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Floor Cleaning CLEANING SCHEDULE

1. Sweep or vacuum. Establish a regular cleaning schedule based on
2. Dilute approved cleaning agent with hot water coach use. The following schedule is suggested:
according to the manufacturer’s directions.
3. Spread cleaning solution across floor.
Daily
1. Gently beat upholstery, then brush or vacuum.
4. Allow cleaning agent to act for a few minutes.
2. Sweep or vacuum floor.
5. Wash the floor. Vinyl floors require broom or
machine scrubbing. 3. Wash floor as necessary.
6. Absorb the dirty water with a mop or wet vacuum. 4. Wipe vinyl and plastic surfaces as needed.
7. Thoroughly rinse the floor with clear water.
Weekly
8. Vacuum or mop excess water and leave to dry. 1. Gently beat upholstery, vacuum, then wipe with a
clean, damp cloth.
CAUTION 2. Sweep and wash floor.
3. Wipe vinyl and plastic surfaces.
Only use approved cleaning agents, dilutions 4. Inspect for stains and treat.
and procedures. Failure to care for flooring
may damage its appearance, cause loss of slip Quarterly
resistance or void the warranty. 1. Vacuum upholstery, remove stains, then shampoo.
2. Sweep and scrub floors. Remove stains.
Vinyl Covers and Trim
SERVICE PROCEDURES
Use mild household detergents such as No. 409
Cleaner with warm water and apply with a sponge or soft Vinyl Floor Covering Repair (Hole under 1/2”)
cloth. A soft bristle brush may be used after the 1. Mask around the outer edge of the hole.
detergent has been applied to the surface. Use a
2. Fill flush with approved caulking of a matching color.
non-abrasive cleaner such as Bon Ami for embedded
dirt. Before the surface dries, wipe with a clean, dry cloth 3. Remove the excess caulking with a putty knife.
to remove residue. 4. Allow to set for 2 minutes. Remove masking tape.
5. Prohibit traffic for two hours.

CAUTION Vinyl Floor Covering Repair (Small Patch)

1. With a sharp utility knife and straight-edge, cut out
Do not use harsh solvent cleaners such as the damaged flooring.
Lestoil or Fantastic, or abrasives. These 2. Clean the plywood floor. Ensure that there is no old
cleaners cause cracking, crazing and adhesive.
deterioration of the vinyl and thread.
3. Cut a patch of new flooring to fit the opening.
4. Mask the edges of the opening and patch.
Badly stained vinyl surfaces can be rejuvenated with
Color Hit, a flexible color coating made by Advance 5. Following the manufacturer’s instructions and
Color Corporation, Los Angeles, California. safety guidelines, glue the patch in place with
contact cement.
Modesty Panels and Driver’s Shield 6. When the adhesive is set, fill the seam around the
Clean modesty panels with mild detergent and water. patch with approved caulking. Fill flush.
Tar, gum, etc., may be removed with a solvent such as
7. Remove excess caulking with a putty knife.
kerosene. Volatile solvents, such as acetone, are not
recommended. After using a solvent, clean the area with 8. Allow to set for 2 minutes. Remove masking tape.
mild detergent and water. 9. Prohibit traffic for two hours.

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Vinyl Floor Covering Repair (Large Patch) Destination Sign Removal

1. With a sharp utility knife and straight-edge, cut out 1. Unplug the sign harness from the socket on the
the damaged flooring. left-hand windshield post (Figure 2).
2. Thoroughly clean the plywood floor by wire 2. Turn the Dzus fastener on the right-hand side of the
brushing or sanding. sign box to release the box from the bracket on the
3. Remove sanding dust and other foreign matter. The center windshield post.
floor must be clean before applying adhesive. 3. Lift the right-hand end of the sign assembly up and
4. Cut a patch of new flooring to fit the opening. out to free the hooks on the right-hand end of the
5. Following the manufacturer’s instructions and box from the bracket on the center windshield post.
safety guidelines, apply approved adhesive. 4. Pull the box to the right to free the pins on the
6. Following the manufacturer’s cure and open left-hand end of the box from the bracket on the
requirements, install the new flooring. left-hand windshield post.
7. Ensure thorough adhesion by rolling or weighting 5. Place the sign assembly face down on a firm
the new flooring. padded surface to avoid scratching or damaging
8. Fill the seam with approved caulking, as above, or the sign window.
hot weld the seam as approved by the flooring
manufacturer.
Driver’s Seat Replacement MOUNTING
1. For easier access, remove the driver’s grab rail by HOOK
SIGN MOUNTING BRACKET ON
removing the two screws on the back and at the CENTER WINDSHIELD POST
front of the modesty panel.
2. Tilt the steering wheel up and out of the way by
pulling the lever on the left of the steering column
toward the steering wheel. DZUS
FASTENER
3. For air ride seats: Disconnect the airline from the air MOUNTING PIN
fitting on the bottom of the seat.
4. Remove the four capscrews that attach the base of
the seat to the floor.
5. Lift the seat up and out. 4---PRONG PLUG ON
6. Install the new seat in the reverse of removal. Torque SIGN HARNESS
the capscrews to 45 --- 55 lb-ft.
SIGN MOUNTING ELECTRICAL SOCKET
Sign Curtain Repair BRACKET ON L.H. ON L.H. WINDSHIELD
If a sign curtain is torn, repair it with 3M polyester tape WINDSHIELD POST POST
or equivalent. Put tape on both sides of the curtain.
To add curtain inserts, butt splice or overlap inserts
and apply a strip of 3/4-inch-wide (19 mm) polyester FIGURE 2
tape over the front and rear seam.

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CURTAIN ROLLER

SIGN BOX

THREADED ROD
INNER JAM NUT
CURTAIN
CAP NUT

ILDER ROLLER TUBE

CURTAIN ROLLER
RETAINER
ROLLER END FLANGE
CAP NUT 2835

FIGURE 3

Destination Sign Disassembly

See Figure 3. PULL OUT
1. Remove the four screws on the sides of the back
cover, and lift off the cover.
GRASP HERE
2. Remove the fluorescent light tube from the sign.
3. Manually unwind either curtain roller until there are a
few inches of slack in the curtain. This allows the
other roller to be removed by popping the end of the
roller out of the roller retaining slot.
4. Lift the end of the roller and the curtain clear of
obstructions in the sign box, and then, taking care
not to crease or tear the curtain, pull the other end
of the roller free from the spindle.
5. Wind the remaining curtain from the freed roller onto 2832
the roller in the sign box. Wind until the end of the
curtain and the fastening are exposed. FIGURE 4
6. Pull one of the flanged ends off the end of the roller 8. Hold the roller steady and grasp both edges of the
so that the end of the strip holding the curtain in the curtain just above the roller groove and carefully
roller groove is accessible. pull the curtain and retaining strip out of the roller
7. Remove the tape securing the curtain ends to the groove (Figure 4). When the curtain and retaining
ends of the roller. strip are freed from the roller, remove the strip.

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9. Roll all of the curtain that was on the freed roller and 9. Pull out an additional length of curtain so that the
all that is in the sign box onto the roller that is still in free end can be fastened to the curtain roller that is
the sign housing. outside the sign box.
10. Remove the roller and curtain from the sign 10. Place the curtain retaining strip in the crease at the
housing using the roller removal procedure above. end of the curtain.
11. Insert the edge of the creased curtain and the end
Note: Make a note or mark from which roller retaining of the retaining strip at the end of the groove in the
slot and spindle the roller and curtain are removed so curtain roller.
they can be reinstalled correctly.

Idler Roller Tube Replacement

If replacing the idler roller tubes, continue: PULL IN
1. Remove the capnuts from the ends of the threaded
rods passing through the idler rollers. Loosen the GRASP HERE
jamnuts (inside the housing) on the threaded rod.
2. Turn the left end of each threaded rod until the
jamnut on the right end can be removed, then turn
the rod in the opposite direction until the left jamnut
can be removed.
3. Slide the rod out of the idler roller tube and out of the
housing.
4. Remove and discard the idler roller tubes.

Destination Sign Assembly

2833
1. If replacing idler roller tubes, position one of the new
tubes in the sign housing. Slide a threaded rod FIGURE 5
through the hole in either end of the housing and
through the idler roller tube.
12. Slide the curtain and retaining strip into the groove
2. Place one of the jamnuts on the inside of the
(Figure 5).
housing and screw the rod into it and out through
the hole in the end of the housing. Continue turning 13. Secure the ends of the curtain at the ends of the
the rod until enough of it has passed through the roller with short pieces of strapping tape.
housing to allow putting a jamnut on the inside of 14. Roll the curtain onto the empty roller until the
the other end. Reverse direction of the rod’s desired reading is displayed in the sign window.
rotation and screw it back through the jamnuts until
15. Replace the fluorescent light tube.
equal lengths of rod are protruding from each end
of the box. 16. Install the back cover.
3. Tighten the jamnuts and put the cap nuts on the
outside ends of the rod. Repeat the process to Destination Sign Installation
install the other idler roller and threaded rod. 1. Insert the two pins on the left-hand of the sign into
the bracket on the left windshield post. Push the
4. If a new curtain is being installed, replace the curtain
right-hand end of the sign forward until the hooks
on the curtain roller.
on the right-hand end bracket enter the holes in the
5. Install the curtain roller and curtain on. Install the center windshield post mounting bracket.
roller in the same slot from which it was removed.
2. Lower the sign slightly to allow the hooks to engage
6. Pull out the curtain and feed it over, behind and the bracket.
under the nearest idler roller.
3. Insert and turn the Dzus fastener until it engages the
7. Pull the curtain until it passes across the window to retaining spring in the bracket.
the other idler roller.
4. Plug the sign harness into the socket on the
8. Feed the curtain under, behind and over the roller. left-hand windshield post.

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 3B-8

SERVICE TOOLS
SOME TOOLS USED FOR THE MAINTENANCE PROCEDURES OUTLINED IN
THIS SECTION ARE NONSTANDARD. THEY ARE AVAILABLE FROM MOTOR
COACH INDUSTRIES SERVICE PARTS OR, WHERE PRACTICAL, MAY BE
FABRICATED AT THE SERVICE FACILITY.

4153

20 -- 361: Extractor -- Insert Lamp

SPECIFICATIONS
Driver’s Seat
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . National Seating (basic)
Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93-B
Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mechanical
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Isringhausen (optional)
Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6800
Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Air-Ride
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . USSC (optional)
Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9100ALX
Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Air-Ride
Passenger Seats
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . National Seating (basic)
Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4210-S
Mechanical Destination Sign
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Transign
Electronic Destination Sign
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pocatec
Floor Covering
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . RCA Rubber
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Taraflex
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Altro
Upholstery
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . John Holdsworth & Co. Ltd.
Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Holdsworth Vigor

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 3C-1

SECTION 3C

DOORS
CONTENTS OF THIS SECTION

SUBJECT PAGE
Entrance Door
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3C-3
Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3C-3
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3C-3
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3C-4
Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3C-4
Lubrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3C-5
Lock Control Solenoid Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3C-5
Manual Air Dump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3C-5
Door Locking Cylinders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3C-6
Door Actuating Cylinders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3C-7
Quick Exhaust Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3C-8
Door Seal Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3C-9
Baggage and Service Compartment Doors
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3C-10
Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3C-10
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3C-10
Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3C-10
Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3C-11
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3C-11
Emergency Escape Hatches
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3C-12
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3C-12
Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3C-12
Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3C-12
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3C-12
Service Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3C-13
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3C-13

MOTOR COACH INDUSTRIES

Printed in Canada.
Date March 2003 Page 3C-2

DOOR LOCKING
CYLINDER

LATCH ASSY

ENTRANCE DOOR
CYLINDER

CONTROL MODULE
HOOK-UP

ENTRANCE DOOR
DAMPER

FIGURE 1

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 3C-3

ENTRANCE DOOR
GENERAL DESCRIPTION Air Locking Cylinders
Two locking air cylinders hold the door closed during
The coach has an air-operated, electrically controlled coach operation. An override valve provides for
sedan-style entrance door that is hinged at the bottom emergency door opening. The air locks are
front and at the dash level. There is a double-glazed automatically actuated via a solenoid valve on the
glass window in the upper section of the door and an control module that is energized by a proximity sensor
acrylic window in the lower section. Door actuation located on the lower latch housing.
switches are located on the driver’s switch panel and on
the exterior, adjacent to the door. Door Switches
The door is operated from inside the coach by a
The door is operated by a control assembly and an air
momentary-on switch on the switch panel. Operating
cylinder assembly (Figure 1) accessed through
the door from outside the coach is done with the
fiberglass panels in the passenger modesty panel. The
momentary-on switch adjacent to the door. The switch
air cylinder and damper are accessed through the spare
must be held in the desired position until the door has
tire compartment at the front of the coach.
completed its movement.
Two locking air cylinders hold the door closed during
coach operation. An override valve provides for
emergency door opening. The cylinders are accessed
through a hole in the transom panel above the door (the
emergency exit decal panel must be removed first).

COMPONENTS
Door Assembly
The door is constructed of molded fiberglass. It has a
stainless steel upper and lower hinge pin that pivots
inside a spherical bearing.
The grab rail is molded polyurethane over steel tube.
The door has a lockable handle with dead bolt.
FIGURE 2
Door Control
OPERATION
The door control consists of a control panel, door
latches, and an air cylinder with a shock absorber to Opening
guard against sudden opening or closing. An air Actuating “open” on either interior or exterior
distribution block connects the cylinder to the control switches energizes the valve panel’s control and
valves in the control panel. latching relays. The door air locking solenoid valve is
interrupted when the latching relay is energized. This
Control Module exhausts the air from the spring-loaded locking
The control valve panel assembly regulates the air cylinders and releases the door air locks (the upper latch
flow to and from the cylinder, and to the latches. The first, and then the lower latch). The control relay supplies
control panel is behind an access panel in the current to the cylinder 4-way air control solenoid valve.
passenger modesty panel. The panel is fitted with 4-way This pressurizes the rod side and exhausts the piston
air control solenoid valves, and a pressure regulator on side of the air cylinder portion, causing the cylinder to
the air circuit. (Figure 2). extend. As the air cylinder rod extends or retracts, it
moves the pivot lever to which it and the upper door
Door Cylinder hinge are attached, moving the door open.
The two-part cylinder is air operated. The When the door is open and the door switch is
double-acting air cylinder portion opens and closes the released, the control relay is de-energized. Locking
door. A shock absorber guards against sudden opening pressures are controlled by the pressure protection
or closing. valves.

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 3C-4

Closing Vertical Alignment

Actuating “close” de-energizes the latching relay. The To access the lower hinge, remove the right front
4-way valve pressurizes the piston side port of the air bumper. To access the upper hinge, remove the lower
cylinder portion, and exhausts the rod end, causing the dash panel and adjacent panel. Adjust door height by
cylinder to retract. turning the hex nuts (Figure 3):
When the door switch is actuated at complete 1. Dump the air in the control system.
entrance door closure, a signal goes to Relay Module 5 2. Turn the battery disconnect switch OFF.
through the main harness to the the latching solenoid
3. Loosen the jamnut on top of each hinge pin.
valve, which is energized via the latching relay and
micro-switch ground to deliver air to locking cylinders 4. Rotate the nut on the bottom of the pin upward or
that lock the door. downward as required.
5. After adjusting, tighten the upper jam nut.
Switches
If either door switch is released during opening or NOTE: Adjusting the door height should not be
closing, the lock solenoid valve is energized and applies necessary under normal conditions.
air to the flow valve, locking the door in that location.

MAINTENANCE Longitudinal Adjustment

To move the door forward or back, reposition the
ADJUSTMENT upper and lower hinges.
All components of the door control system have to
1. Dump the air in the control system.
operate correctly and in sequence. Before adjusting the
door control assembly, first check the door-to-jam 2. Turn the battery disconnect switch OFF.
alignment. 3. Remove the fabric panels from the inside of the
The door must move in and out of the opening without door.
binding or distortion. Ensure that the door is not binding 4. Loosen the bolts connecting the door to the hinge.
on front or rear posts, at the top header or at the bottom 5. Slide the door back or forward on the hinge.
step well. Adjust the alignment as required. 6. Tighten the slots and replace the panels.

FIGURE 3

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 3C-5

Fine Adjustments LOCK CONTROL SOLENOID VALVE

Reposition the dovetail wedges (Figure 4) for fine
Removal
adjustments to the door latching fit. The wedges on the
1. Turn the battery switch OFF.
door adjust up and down, and those on the frame adjust
lateral position. 2. Remove the panel from the passenger modestly
panel to gain access to the control module.
3. Remove the two screws holding the valve to the
manifold.
4. Remove the valve.
Installation
1. Reverse the order of Removal.

MANUAL AIR DUMP

If the electrical circuit fails, a hand-operated air valve
allows air to be exhausted from the door operating
cylinders (Figure 5). The air dump valve is under the
dash to the right of the steering column.

FIGURE 4

Control Adjustments
Normally, the door will open in 5.6 seconds, and close
in 5.0 seconds. If the door takes too long, check the
pressure setting on the regulator valve.

AIR DUMP VALVE

LUBRICATION
The only lubrication required is the universal joint on
the air cylinder. FIGURE 5

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 3C-6

DOOR LOCKING CYLINDERS

Lubricate the entrance door locking air cylinders
through the air hose connector at approximately 50,000
mile (80,000 km) intervals. Lubricate them with
specification S-6 (Heavy-Duty Engine Oil - 10W).
CYLINDER
Removal
The entrance door header locking cylinder is behind
the transom panel above the door (Figure 6).
1. Turn the battery switch OFF.
LOCK ASSEMBLY
2. Open the entrance door fully and release air from
the system by opening the overrule valve.

NOTE: If the valve is equipped with a monitor, remove

it.

3. Remove the emergency exit decal panel above the

door.
4. Disconnect the air tubing.
5. Remove the mounting bracket and cylinder
assembly from door header.
6. Remove the hex nut and disassemble the cylinder
from the mount bracket.

Installation

NOTE: When overhauling air cylinders, replace all

seals, felts, cups and o-rings. Coat new parts with oil
before assembly.

1. Install by reversing the removal procedure.

2. Check the air cylinder for leakage.
3. Adjust the cylinder and claw reach or the cylinder
latch-to-door striker plate adjustment. FIGURE 6

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 3C-7

DOOR ACTUATING CYLINDER 7. Remove the shoulder bolt attaching the rod end to
An air cylinder actuates the door. A shock absorber the pivot lever and bracket.
buffers the piston as air pressure is applied (Figure 7). 8. Remove the cylinder from the pocket.
NOTE: When repairing the cylinder, remove old
Removal
o-rings and seals. Do not damage grooves or
1. Turn the battery switch OFF. surfaces with sharp tools. Thoroughly clean all parts,
2. Open the door fully and release air by opening the and when installing seals apply a thin film of o-ring
overrule valve. grease.
3. Open the spare tire door.
4. Remove the right bumperette and the front right Installation
panel. 1. Reverse the removal procedure, and check the
5. Disconnect all air tubing. cylinder for air leaks.

6. Remove the pin attaching the cylinder to the rear NOTE: Cylinder ports with elbow fittings must be
mounting bracket. pointing outward (to the left).

12 1 23 4 5 6 7 8 9 10 11

1. FITTING 5. WEAR RING 9. FITTING

2. O-RING 6. O-RING 10. U-CUP
3. CUSHION CUP 7. PISTON 11. WIPER
4. U-CUP 8. PISTON ROD 12. PIVOT HOLE

FIGURE 7

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 3C-8

QUICK EXHAUST VALVE NOTE: If the quick exhaust valve does not function
properly or leaks excessively, replace or repair it.
The quick exhaust valve, located behind the lower
latching cylinder, should have an Operational and The quick exhaust valve should be removed,
Leakage Test done every 50,000 miles (80,000 km), or disassembled, cleaned and inspected every 100,000
1,500 operating hours (Figure 8). miles (160,000 km) or 3,000 operating hours. Replace
worn or damaged parts.
SUPPLY
Removal
1. Turn the battery switch OFF.
2. Block the coach.
3. Remove the main latch assemblies.
DELIVERY
4. Disconnect the air lines.
DELIVERY
5. Remove the valve from the T behind the cylinder.
Disassembly
1. Remove the flange screws or nuts and separate the
SEALING RING EXHAUST
DIAPHRAGM two body halves.
2. Remove the sealing O-ring and diaphragm from
between the body halves.
QUICK-RELEASE VALVE
3. Clean all parts in cleaning solvent, and check the
interior valve body halves for corrosion, pitting or
FIGURE 8
nicks. Replace as required.
NOTE: Always replace the diaphragm and sealing
ring.
Operating and Leakage Test
1. Make and hold a full brake application of Assembly
approximately 80 psi (552 kPa). 1. Center the diaphragm in the upper body half, and
position the o-ring on the lower body half.
2. Remove the panel at the door latch by lifting the
tabs. 2. Reassemble the body halves.
3. Install the cover fasteners and torque the fasteners
3. Coat the exhaust port with soap solution. Leakage
evenly to 60 in-lbs (6.78 NSm).
of a one-inch bubble in three seconds is permitted.
4. Coat the valve body and cover. No leakage is Installation
permitted. 1. Reverse the removal procedure.

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Printed in Canada.
 Date March 2003 Page 3C-9

DOOR SEAL REPLACEMENT 2. Remove the seal and discard it.

3. Install the new seal using a rubber mallet or other
The door outer seal is a single piece (Figure 9).
gentle pressure to seat the seal. There should be
1. Open the entrance door completely, exposing the about 1/2” (1 cm) clearance between the bottom of
door frame. the seal and the floor of the stairwell.

A
A

A---A

FIGURE 9

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 3C-10

BAGGAGE AND SERVICE COMPARTMENT DOORS

GENERAL DESCRIPTION COMPONENTS
Baggage and service compartment doors are Engine Service Doors
secured by hinged doors or access covers.
The rear engine compartment is accessed through a
The coach has keyed-alike locks on baggage and service door at the rear of the vehicle and a service door
service doors. The electrical baggage door locking on the right rear side of the vehicle below the belt line.
systems automatically lock with release of the parking
brake. Rear Curbside Service Door
This door is front four-bar link stainless steel hinged.
The door latch is activated by a paddle handle with an
integral FOMOCO keyed-alike lock held by two latches
operated by a central actuator. This door provides
access to the air conditioning compressor, lavatory
dump valve, right rear taillights and rear engine
compartment door release.

LOCKING SYSTEM
The locks operate electrically. To unlock the baggage
doors, the parking brake must be applied.

MAINTENANCE

NOTE: If a baggage door locks too tightly or too

loosely, adjust the upper or lower catches on the
inside edges of the baggage compartment.

INSPECTION
1. Inspect the pulley cables for fraying. Replace as
necessary.
2. Check the pulleys for wear and cracks. Replace as
FIGURE 10. Baggage Door Hinge and Cable necessary.

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 3C-11

REMOVAL 5. Remove the screws that secure the hinge panel to

the coach body and remove the door, stabilizer tube
Baggage Door
and hinge panel as an assembly.
NOTE: Baggage door removal should be performed
by two people.
Cable Spring Assembly Removal
1. Turn the battery switch OFF. 1. Remove the cable end/spring plug from the spring
2. Fully open the baggage door and support it to by rotating the plug.
prevent it from falling when cables are removed.
2. Remove the four capscrews that mount the spring
3. Using the baggage door cable pulling tool (20-46),
pull the cable back to allow removal of the clevis retainer to the upper compartment ceiling channel.
pins that attach the pulley cables to the stabilizer 3. Rotate the spring to remove it from the spring
tube (Figure 11). retainer.

WARNING Hinged Service Doors

1. Turn battery switch OFF.
The baggage door mechanism’s cable 2. Open the door and support it to prevent it from
assembly is under tension. To prevent falling when hinges are removed.
injury, exercise extreme caution during
removal and installation. 3. Remove all prop rods or spring clip assemblies from
the door.
4. Remove the stabilizer tube from the mounting 4. Remove all hinge fasteners and remove door from
brackets. the coach.

WARNING NOTE: To remove the battery door’s small disconnect

switch door, remove the inner fiberglass panel to
access the fasteners.
Support the baggage door at this stage to
prevent it from falling during final removal
procedures.

INSTALLATION

NOTE: Replacement baggage and service

compartment doors are provided without locking
systems.

Baggage Door
1. Install the springs and cables by reversing the
removal procedure.
2. Position and support the baggage door in the
fully-open position, and reverse the removal
procedure.

Hinged Service Doors

1. Position and support the door in the fully-open
position, and reinstall the prop rod, spring clips and
FIGURE 11 hinge fasteners.

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 3C-12

EMERGENCY ESCAPE HATCHES

GENERAL DESCRIPTION MAINTENANCE
Two escape hatches are located in the roof. The
hatches are used for emergency exit (Figure 12). ADJUSTMENT
Open the emergency hatch and examine the surface
of the rubber seal surrounding the hatch opening. If the
contact impression is a continuous, unbroken line, the
1 seal is good and requires no adjustment.
When adjusting the escape hatch for proper locking
or sealing, always check that the handle and locking rod
mechanism is adjusted for maximum contact with
locking lugs and/or catches.
1. Unfasten the catches on both sides of the hatch
opening and move the catches up, down, front or
back as required to adjust the hatch cover.
NOTE: If additional forward or rearward adjustment
is required, it may be necessary to remove the
catches and elongate the slotted holes.

2 2. Chalk the edge of the hatch.

3. Close and check the seal to determine if the hatch is
centered; readjust it if necessary.

REMOVAL
1. Turn battery switch OFF.
2. Unfasten the hinge mountings and remove the
access cover.
3. Remove the seal material from the mount ring
trough, and drill out the mounting rivets to remove
the mounting ring.

INSTALLATION
3 1. Reverse the removal procedure.
2. Adjust the closure as required.

FIGURE 12

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 3C-13

SERVICE TOOLS
SOME TOOLS USED FOR THE MAINTENANCE PROCEDURES IN THIS
SECTION ARE NONSTANDARD. THEY ARE AVAILABLE FOR PURCHASE
FROM MOTOR COACH INDUSTRIES SERVICE PARTS. WHERE PRACTICAL,
THEY MAY BE FABRICATED AT THE SERVICE FACILITY.

2705

P/N 20-46 Baggage Door Cable Puller

SPECIFICATIONS
DOOR CONTROL ASSEMBLY
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MCI
DOOR ACTUATING CYLINDER
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Air Draulics
SEDAN DOOR LOCKING CYLINDERS
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Clippard
BAGGAGE DOOR ASSEMBLY
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MCI
ESCAPE HATCH
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MCI
PADDLE LATCHING HANDLE
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MCI
ELECTRIC SOLENOID LOCK
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . GM

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 3D-1

SECTION 3D

WINDOWS
CONTENTS OF THIS SECTION

SUBJECT PAGE
Windows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3D-2
Windshields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3D-2
Driver’s Window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3D-2
Side Windows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3D-2
Windshield Wipers/Washers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3D-3
Windshield Wipers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3D-3
Windshield Washers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3D-4
Wiper/Washer Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3D-4
Window Blinds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3D-5
Manual Roller Shades . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3D-5
Motorized Roller Shades . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3D-6
Service Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3D-6

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 3D-2

WINDOWS
WINDSHIELDS DRIVER’S WINDOW
The windshields are installed into a flange around the Remove the driver’s window by first removing all
opening and held in place with a one-piece rubber screws from the interior retaining frame. Then remove
moulding. the glass from the rubber retainer.
Proper installation is necessary to reduce or prevent NOTE: During removal and installation of the driver’s
stress. Glass from different manufacturers may vary in window, take care to ensure proper placement of all
size and shape. Check non-MCI windshields for proper window components.
size and curvature. The rubber seal allows for a
5/16-inch difference in windshield curvature.
SIDE WINDOWS
WINDSHIELD REMOVAL
Read the entire procedure before starting.
All the coach windows are emergency escape except
NOTE: Two people are required to remove the the #1 front window on each side of the coach. These
windshield; one inside to push the glass out, the other non---bonded side windows are top hinged, and open
outside to catch the glass. from the inside.
To open, lift the release bar at the lower edge,
disengaging the safety latches. Push the window out.
WARNING Emergency instructions are attached to the release
bars.
Wear protective gloves when handling glass. To remove a non-bonded window after opening,
remove the screws and retainer clips and swing the
window out far enough to disengage the frame
1. Remove the acorn caps from each wiper arm.
extrusions. Lower the window from the opening.
2. Disconnect the washer hose.
3. Pull the arm off the spindles. SIDE WINDOW GLASS REPLACEMENT
4. Remove the plastic caps. 1. Find the spot where the two ends of the retaining
rubber meet and pry one end out.
5. Remove the lacing from the seal.
2. Remove the retaining rubber around the glass from
6. Run a fiber stick between the glass and the seal all the interior side of the frame.
around the window.
7. Push out the top outer corner first. SIDE WINDOW INSPECTION
Before each run, ensure that all side windows are
WINDSHIELD INSTALLATION latched. A protrusion of 1/4” (6 mm) or more indicates
1. Liberally apply soap all around the seal. that a window is not properly latched.
2. Insert the windshield pane into the seal and work it
in with a fiber stick at the top and bottom near the
center post.
WARNING
3. Work the windshield into the seal at the center of the
outer edge, then the top and bottom outer corners. Do not open the side windows while the
coach is moving.
4. Slide the windshield into the seal along the center
post to 1/8” from full engagement. Windows close with enough force to
5. Reinstall the lacing into the seal. cause injury. Ensure that hands are clear.
6. Reinstall the wiper arms.

MOTOR COACH INDUSTRIES

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 Date March 2003 Page 3D-3

WINDSHIELD WIPERS/WASHERS
WINDSHIELD WIPERS
WARNING
There is one windshield wiper for each windshield. A
single motor with center idler and drive links powers the
wipers (Figure 1). The controls are on the turn signal DO NOT remove the motor before dis-
lever. The wiper motor is removable from the coach connecting the harness. The motor may
cycle and cause personal injury.
exterior, through the black acrylic valence below the
windshield.
8. Disconnect the wiper motor from its harness.
9. Remove the wiper motor from its mounting bracket.
WIPER MOTOR INSTALLATION
WIPER BLADE 1. Mount the motor.
2. Connect the motor to the harness.
WIPER BLADE 3. Turn the motor on and off so that it parks itself.
4. Disconnect the harness.
5. Connect the drive link, ensuring that it is parallel to
the motor output shaft.
6. Position the valence in the opening and lacing.
7. Replace plastic arm caps.
WIPER MOTOR 8. Replace the wiper arm in the park position. The
blades must be parallel to the center post and 4
DRIVE LINK inches (10 mm) away from it.
9. Replace the windshield washer hose.
10. Tighten the acorn nut on the spindle.
11. Test the wiper sweep for symmetry. The wiper
LINK blade should be 4 inches (10 mm) from the center
WIPER CRANK post at both the top and bottom tips. If not, remove
CENTER IDLER LINK the wiper arm and reposition it.

FIGURE 1 WIPER ARMS AND BLADES

1. Ensure that the motor is in the park position.
2. Ensure that the blade is assembled in the blade
saddle correctly. Tighten the screw and nut
assembly until it is snug. The blade should have
WIPER MOTOR REMOVAL free movement in the saddle; do not crush the
1. Remove the acorn nuts from each wiper arm. saddle over the blade.
2. Remove the wiper washer hose from the arm. 3. If saddle portion of arm is not attached to the arm,
ensure that the saddle is on the inboard/inner wiper
3. Pull the arm off the spindle. arm, not on the outer.
4. Remove the plastic caps. 4. Install the wiper arms and tighten the acorn nuts.
Parts should move freely in their bearings.
5. Pull out the lacing around the valence by prying out
one corner and slowly working out the rest. 5. Turn the motor on and check the wiper pattern.
Ensure that the blades do not hit the window seal.
6. Remove the valence. 6. If the sweep is off center, move main arm clockwise
7. With a screwdriver, snap the main drive link off the or counterclockwise on the diameter segment to
crank. center the sweep.

MOTOR COACH INDUSTRIES

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 Date March 2003 Page 3D-4

WINDSHIELD WASHERS The control for the wipers and washer is on the turn
signal lever.
An electric windshield washer pump is installed in the
left front service compartment (Figure 2). Activate the washer by pushing the sleeve in towards
the steering column.

WASHER RESERVOIR REMOVAL

NOTE: If there is still fluid in the reservoir, you will

need a basin to catch the remaining fluid.

1. Loosen the holding straps by lifting the two buckles.

2. Remove the holding straps.
3. Reach behind the reservoir and unplug the harness.
FIGURE 2 4. Raise the reservoir and unplug the hose.

WIPER/WASHER TROUBLESHOOTING
SYMPTOM PROBABLE CAUSE REMEDY
Motor does not operate. Low or no voltage. Check electrical connections and fusing. See
Section 7.
Linkage locked up. Check that the transmission shaft has been prop-
erly inserted. Also check the drive pin for excess
wear and proper lubrication. Check to see if the
linkage is hitting against the coach window side.
This may be due to an improperly-sized drive bar
or pin, pulling the linkage out of its proper line of
travel.
Relay failure. Replace the relay. (See Dash Harness and Module
Installation in the Parts Manual)
Motor operates, but wip- The shaft is operating but the Check if the arm driver is cracked, or has become
er arm does not move. arm does not move. disengaged through wear or some other cause.
Fails to spray. Reservoir empty. Add proper fluid.
If temperature is below 32_F Store the coach or parts in a heated area. Then
(0_C), reservoir has wrong wash- purge the system with a low-temperature solution.
er fluid—it is frozen.
Contamination in tubing or Remove the contamination with compressed air. If
nozzles. the system is severely clogged, replace the neces-
sary items.
Tubing damage. Replace the affected section.
Tubing bent (kinked) or off one Realign the tubing and/or refit it. Trim the end to
or more connections. ensure proper fit or replace the tubing.
Weak spray. Tubing failure. Replace the tubing.
Improper solution. Replace with proper type solution.
Jet stream improperly directed. Reposition the nozzles.
Pump loose prime. Faulty check valve. Replace check valve.

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 3D-5

WINDOW BLINDS
MANUAL ROLLER SHADES S If spring tension is too little, increase by winding
clockwise a few turns.
Spring (Speed) Adjustment 5. Insert the shade into the brackets. Try the shade. If
1. Pull shade down 4” --- 6” (10 - 20 cm) ensuring that movement is unsatisfactory, repeat procedure.
the shade locks into position.
2. Open the bracket and carefully remove the roller Lubrication (6 - 8 months)
shade, ensuring that the shade is not forced as this
can unlock the spring. (Figure 3)

FIGURE 5
FIGURE 3
1. Pull down shade completely.
3. Gently slide the winder key over the spring nozzle as 2. Using a small screwdriver, grab both felt bumpers
shown (Figure 4). Ensure that the spring does not located directly below the top two end stops in both
become unlocked. side channels and slide them down until they sit on
top of the roller shade bottom guides.
3. Apply several drops of silicone directly on top of
both felt bumpers to make them moist (not dripping
wet).
4. Grab the bottom bar of the shade and let the shade
move up all the way. The shade will move both felt
bumpers along until they come to rest again below
the two top end stops.
Cleaning
If excessive dust has settled on the screen fabric, it
can be wiped clean with a soft sponge or cloth and
water. Touch the fabric only very lightly, ensuring that
fabric does not stretch.
Leave shade down until dry.
FIGURE 4 To clean tougher spots or stains, the shade needs to
be removed and placed on a flat surface. Wipe the fabric
with a soft sponge or cloth, using soap or a mild
4. Adjust the spring tension if necessary: detergent. Wipe the screen dry with a soft cloth, roll it up
S If the spring is completely unwound, wind the into the same position it was in when taken out and fit it
spring clockwise approximately 24 turns. back into brackets.
S If spring tension is too much, decrease by Pull down shades into the closed position and leave
winding counterclockwise a few turns. until dry.

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 3D-6

MOTORIZED ROLLER SHADES Limit Settings

The power supply must be stable for the motors to Push the appropriate limit switch button located
function properly. behind the valance access hole (Figure 6) and drive
shade into desired position. Press the switch to set the
limit.
If the shade moves up when down is pressed, reverse
the polarity of the motor cables on the switch.
Each motor has a separate limit switch setting button,
one for lowering and one for raising of the shade.

COLOR OF LIMIT MOTOR ON LEFT MOTOR ON

BUTTON SIDE OF SHADE RIGHT SIDE OF
SHADE
BLACK BUTTON LOWERING SHADE RAISING SHADE

FIGURE 6 YELLOW BUTTON RAISING SHADE LOWERING SHADE

SERVICE TOOLS
SOME OF THE TOOLS USED FOR THE MAINTENANCE PROCEDURES IN THIS
SECTION ARE NONSTANDARD. THEY ARE AVAILABLE FOR PURCHASE
FROM MOTOR COACH INDUSTRIES SERVICE PARTS. WHERE PRACTICAL,
THEY MAY BE FABRICATED AT THE SERVICE FACILITY.

2703

20-680: Lacing Tool, 9/16-inch Eye

Passenger Window Blind Adjustment Tool

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 3E-1

SECTION 3E

LIFTING
CONTENTS OF THIS SECTION

SUBJECT PAGE
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3E-2
Lifting the Coach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3E-2
Jacking Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3E-3

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 3E-2

GENERAL DESCRIPTION
These procedures and safety precautions must be WARNING
followed.
NOTE: MCI recommends using a drive-over pit for The front axle does not have parking brakes. If
coach servicing. the drive and/or tag axles are being lifted,
block the front tires to prevent rolling.
Use only the specified jacking locations shown in this
section when lifting the coach. Lifting the coach at other
locations can result in body or frame damage. 2. Switch the battery disconnect OFF.
3. Position jacks beneath jacking points. (Figures 1
and 2)
WARNING 4. Support the axles not raised by a hoist with the
appropriate axle stands (See Jacking Points):
Do not go under the coach until it is properly
supported by safety stands. If lifting the entire Lift on the front and drive axles
coach by the axles as a minimum, while support-
ing the tag axle with addition-
LIFTING THE COACH al stands. Preferred: lift all
three axles.

CAUTION If lifting the entire Support all axles with addition-

coach by the body al stands.
If lifting a single axle Support those axles not
Do not raise the coach so that the entire supporting coach weight with
weight of the axles hangs on the shock additional stands.
absorbers or air springs.
5. Raise the coach carefully.
6. After the coach has reached the desired height,
WARNING place axle stands under the axle raised by the hoist.
DO NOT use a hoist as an axle stand.

Before lifting the coach, observe the

following safety measures:
1. Set the parking brake.
2. Put the coach in neutral.
3. Switch the main battery disconnect OFF.
4. Support any axle not raised by a hoist
with stands.
5. After raising the coach to the desired
height, support the hoisted axle with
stands. DO NOT use a hoist as a stand.

1. Put the coach in neutral and apply the park brake.

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 3E-3

JACKING POINTS axle. (Figures 3 and 4) A third pair of stands can be

used on the bogie legs ahead of the drive axle, but only
when the body is also supported at the tag axle bogie
legs. Other locations or combinations of stands may
cause frame distortion or body damage.

FIGURE 1. Drive Axle Jacking Points

FIGURE 3. Front Axle Stand Position

FIGURE 2. Front or Tag Axle Jacking Points

When the coach must be supported by the body with

stands, use the jacking points on the bogie legs located
behind the front axle and the bogie legs behind the tag FIGURE 4. Tag Axle Stand Position

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 3F-1

SECTION 3F

TOWING
CONTENTS OF THIS SECTION

SUBJECT PAGE
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3F-2
Non-Lifted Tow Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3F-2
Axle Shaft Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3F-2
Towing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3F-2
Lifted Tow Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3F-4
Attaching the Coach to the Tow Vehicle . . . . . . . . . . . . . . . . . . . . . . . . . 3F-4
Axle Shaft Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3F-4
Towing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3F-4
Air Connections for Towing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3F-5
Routing the Air Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3F-5
Connecting the Air Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3F-5

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 3F-2

GENERAL DESCRIPTION
These procedures and safety precautions must be
followed when towing a J-coach.
Apply the parking brakes when waiting for assistance
from a tow vehicle.

CAUTION
WHEN TOWING THE COACH:
S Tow from the front of the coach only.
S Use a front axle-lift or wheel-lift style tow
truck.
S Do NOT use sling lift tow trucks; they will
FIGURE 1
damage the coach.
S Drive axle shafts must be removed before
towing.
S Unload the tag axle. CAUTION
S Tow truck operators must be authorized and
experienced in towing intercity coaches.
Do not use a chisel or wedge to loosen the
S Do NOT tow a fully loaded coach. axle shafts and dowels. The chisel or wedge
S Do NOT allow passengers on the coach. can damage the hub, axle shafts and oil seals.

3. Remove the tapered dowels and both axle shafts

NON-LIFTED TOW PROCEDURE from the axle.
4. Secure the axle shafts and loose fasteners in a
AXLE SHAFT REMOVAL baggage bay. Protect the axle shaft splines with a
1. Remove the stud nuts and washers from the flanges heavy rag if possible.
of both axle shafts. 5. Cover the open axle ends to prevent oil loss or
2. Loosen the tapered dowels in the flanges of both contamination. (A round piece of plywood with the
axle shafts as follows: axle flange bolt pattern drilled through it can be
used to cover the axle end.)

TOWING
1. Verify that the park brakes are applied and the
Follow safe shop practice. Wear safety “TOW SUPPLY” is not connected.
glasses. Do not hit the round driving lugs on 2. Position the tow truck so that the truck’s tow bar
the head of the axle shafts. Lugs can break and
contacts the front bumper of the coach.
cause injury.
3. Attach the tow truck chains in the coach tow hooks
a. Hold a 1!@2-inch-diameter brass drift or brass and take up all slack.
hammer against the center of the axle shaft, 4. Attach safety chains as applicable.
inside the round driving lugs (Figure 1). 5. Release the parking brakes before towing the
b. Hit the end of the drift with a five to six pound coach. Check the service brake air pressure on the
hammer and the axle shaft and tapered dowels dash-mounted front and rear air gauges. The
will loosen. pressure must be at least 75 psi (517 kPa).

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 3F-3

6. Operate the coach engine during the tow to

CAUTION maintain brake system air pressure, or attach an
external air pressure line from the tow truck to the
“TOW SUPPLY” valve in the front left service
At least one service brake circuit requires full compartment, below the front junction box (Figure
air pressure, preferably the primary (rear 2). This will automatically release the park brakes.
service brake) circuit. This will allow the park The air pressure must be at least 75 psi 517 kPa).
brake push-pull valve to be released manu- The supplied connection points are 1/4 NPT
ally, allowing the park brakes to retract.
threaded fittings. Mufflers can be removed to install
fittings compatible to the tow vehicle. (See
Connecting the Air Lines later in this section.)

WARNING
CAUTION
Make certain that the coach is securely
attached to the tow vehicle before attaching
the supply line. Otherwise the coach may Do not tow the coach without external air
pressure applied to the tow supply valve,
move, with the potential to cause serious
unless the engine and its air compressor are
personal injury.
in operation. Without system air pressure,
the park brakes may apply automatically if
Note: If both circuits are low, and the air system is parking air pressure falls to approximately
40 psi.
intact, the entire system may be filled through the
connection labelled “TOW SUPPLY.” This will
automatically release the park brakes. If both circuits 7. Observe the normal towing precautions including,
are low and one circuit is damaged, fill the other circuit but not limited to, the ones listed below when
through the connection marked “PRIMARY FILL” or towing the coach:
“SECONDARY FILL.” The park brake must then be a. Do not allow passengers in the coach during
released manually. All fill locations are in the front LH towing.
service compartment, below the front junction box b. Do not exceed a prudent, safe towing speed. Be
(Figure 2). aware of changing conditions.
c. Avoid “tight” turning. Accelerate and decelerate
slowly, with caution.
d. After approximately two miles towing, check
and retighten the safety and tow chains as
necessary.

NOTE: If the entire system is not intact, you can

move the supply connection to the rear service
emergency fill connection (provided the rear system
is intact). Only the rear service reservoir will be filled
and maintained, so the automatic park brake release
system will not work. The park brake must be
manually released by pushing the button down after
the coach is blocked and safely attached to the tow
vehicle. The break-away function will not work with
FIGURE 2 this method of connection.

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 3F-4

LIFTED TOW PROCEDURE ATTACHING THE COACH TO THE TOW

VEHICLE

CAUTION WARNING
Only operators authorized and experienced Make certain that the coach is securely
in towing intercity coaches should tow attached to the tow vehicle before attaching
coaches. Do not use sling lift tow trucks. the supply line, or manually releasing the
parking brake. Otherwise the coach may
move, with the potential to cause serious
If a disabled coach needs to be lifted from the ground personal injury.
for towing, follow the procedure below. Read the entire
procedure before starting.

WARNING CAUTION
Do not lift fully-loaded coaches. The drive axle shafts must be removed
when the coach is being towed.

Use only heavy towing vehicles. These vehicles must 1. Verify that the park brake is applied, and that the tow
have hydraulic booms that can extend under the front of provision supply line is not connected or
the coach to attach directly to the front axle beam if lifting pressurized.
the front of the coach is necessary for towing. An
acceptable alternative to lifted towing is a flat deck or 2. Push the main battery disconnect switch to “off.”
ramp trailer that carries the entire coach. AXLE SHAFT REMOVAL
Careful attachment of towing equipment is the See Axle Shaft Removal, page 3F-2.
responsibility of the towing operator. Therefore, it is very TOWING
important to select an operator authorized and 1. Verify that the park brake is applied, and that the tow
experienced in towing intercity coaches.
provision supply line is not connected or energized.
Note: If both circuits are low, and the air system is 2. Allow the tow operator to extend and connect the
intact, the entire system may be filled through the boom device to the axle beam. The operator may
connection labelled “TOW SUPPLY.” This will want the vehicle to be placed on run-up blocks. If
automatically release the park brakes. If both circuits needed, the run-up block provided with the coach
are low and one circuit is damaged, fill the other circuit is stored in the battery compartment.
through the connection marked “PRIMARY FILL” or 3. If the vehicle cannot move under its own power,
“SECONDARY FILL,” as the case may be. The park connect chains to the tow eyes attached to the
brake must then be released manually. All fill locations frame underneath the bumper and pull the coach
are in the front LH service compartment, below the onto the blocks with the tow vehicle.
front junction box (Figure 2). 4. Attach auxiliary lamps or a light bar to the rear of the
When a vehicle is to be towed, make sure the park coach to provide running and stop lamp functions,
brake is in the Applied (up) position. This will safely keep and connect the lamp harness to the tow vehicle.
the vehicle stationary when the tow vehicle device is 5. Connect both the service and supply tow provision
being attached to the coach. Once the Supply line from lines as outlined in the Air Connection section, then
tow vehicle is attached to TOW SUPPLY and air flow energize the supply line to release the park brakes.
begins, the parking brakes will automatically release to 6. Make a service brake application from the tow
allow the coach to be towed. If this line accidentally vehicle and verify the rear service brake function on
detaches or is severed during towing, pressure loss the coach.
from this line will activate the break-away protection 7. Observe the normal precautions including, but not
function, which automatically reapplies the parking limited to, the ones listed below when towing the
brakes. coach:

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 3F-5

a. Monitor suspension ride height as outlined in the

Air Suspension Control section. Pay particular
attention to the rear of the coach, since when the
front end is raised, the rear of the coach will be
closer to the ground and may contact the
ground when negotiating large bumps, steep
driveways and sharp corners.
b. Do not allow passengers inside the coach
during towing.
c. Do not exceed a prudent, safe towing speed. Be
aware of changing conditions.
d. Avoid “tight” turning. Accelerate and decelerate FIGURE 3
slowly, with caution. 2. Route the tow vehicle hoses around the bumper
e. After towing approximately two miles, check the opening and across the spare tire compartment to
connections between the tow vehicle and the the connection points.
coach, including air and electrical connections. NOTE: Route the hoses away from the steering gear
and linkage.

NOTE: Make certain that the hoses will not be

AIR CONNECTIONS FOR TOWING pinched or damaged when closing the spare tire
The coach has provisions to allow air connections access door.
from the tow vehicle to operate the rear service brakes
and maintain air pressure in the reservoirs. CONNECTING THE AIR LINES
Two lines connect to the tow vehicle, which are similar
to to those for an air-braked trailer:
The connection points are behind the left front service 1. Use the “TOW SUPPLY” connection for the line from
compartment door, below the front junction box (Figure the tow vehicle that charges the air system. (This
2). They have 1/4 NPT threaded muffler devices that the line is sometimes called the Emergency line.) This
tow operator can remove to install the fittings the tow line allows air from the tow vehicle to fill and
vehicle requires. maintain the air pressure in the coach air system. It
assumes that the entire coach air system is intact.
2. Use the “TOW BRAKE CONNECTION” for the line
from the tow vehicle that operates the service
CAUTION brakes. This line energizes only when the tow
vehicle’s brakes are applied, and will operate the
brakes on the two rear axles to help stop the vehicle
Replace the muffler devices on the towing combination.
provision when towing is complete. This will
prevent dirt or water from entering the
When towing is complete, replace the snap-in plug,
system. DO NOT INSTALL SOLID PLUGS.
The park brake may not release properly if licence plate, and muffler devices.
this connection cannot vent to the NOTE: If the entire system is not intact, you can
atmosphere.
move the supply connection to the rear service
emergency fill connection (provided the rear system
is intact). Naturally, only the rear service reservoir will
be filled and maintained, so the automatic park brake
ROUTING THE AIR LINES release system will not work. The park brake must be
1. Route the hoses from the tow vehicle through the manually released by pushing the button down after
spare tire access door in the front bumper (Figure the coach is blocked and safely attached to the tow
3). The opening is behind the center or street side vehicle. The break-away function will not work with
licence plate. this method of connection.

MOTOR COACH INDUSTRIES

Printed in Canada.
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 Date March 2003

SECTION 4
AIR SYSTEM
& BRAKES

A -- Air Systems (Introduction)

B -- Air Compressor and Governor
C -- Air Dryer and Oil Separator
D -- Air Control Components
E -- Brakes
F -- Air Schematics

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 4A-1

SECTION 4A
AIR SYSTEMS (OVERVIEW)
CONTENTS OF THIS SECTION
SUBJECT PAGE
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4A-2
Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4A-2
Air Compressor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4A-2
Governor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4A-2
Cooling Coil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4A-2
Air Dryer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4A-2
Oil Separator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4A-2
Supply Reservoir . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4A-2
Primary and Secondary Service Brake Reservoirs . . . . . . . . . . . . 4A-2
Pressure Protection Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4A-2
Air Manifold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4A-3
Emergency and Suspension/Accessory Reservoirs . . . . . . . . . . . 4A-3
Service Brake Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4A-3
R12-DC Service Brake Relay Valve (Rear Brakes) . . . . . . . . . . . . . 4A-3
QR-1 Quick Release Valve (Front Brakes) . . . . . . . . . . . . . . . . . . . . 4A-3
Antilock Braking System (ABS) Valves . . . . . . . . . . . . . . . . . . . . . . 4A-3
Two-Way Check Valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4A-4
PP-1 Park Brake Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4A-4
RD-3 Emergency Release Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4A-4
SR-1 Spring Brake Control Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . 4A-4
R14 Park Brake Relay Valve (Rear Brakes) . . . . . . . . . . . . . . . . . . . 4A-4
Brake Chambers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4A-5
Accessory Junction Blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4A-5
Entrance Door Control Dump Valve and Control Module . . . . . . 4A-5
Low Air Pressure Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4A-5
Service Reservoir Pressure Transducers . . . . . . . . . . . . . . . . . . . . . 4A-6
Stop Lamp Switches (Service and Park Brakes) . . . . . . . . . . . . . . 4A-6
Primary and Secondary Service Brake Systems . . . . . . . . . . . . . . 4A-6
Fill Provisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4A-6
Towing Provisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4A-6

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 4A-2

AIR SYSTEMS
GENERAL DESCRIPTION Air Dryer
The air dryer is a Bendix AD-IP cartridge type. The air
Many components on the J4500 model coach are dryer removes moisture and the majority of other
powered and/or controlled by compressed air, including contaminants from the air prior to delivery to the oil
service, parking and emergency brakes, suspension separator. The air dryer is located on the curbside tag
and accessories such as the air-powered door. axle bogie leg.
Major system components are as follows:
Oil Separator
The oil separator, located on the curbside tag axle
S air compressor and governor, which provede
bogie leg, is a Bendix PuraGuard. The oil separator
compressed air within a controlled pressure range;
removes those contaminants remaining after air has
passed through the air dryer prior to delivery to the
S air dryer and oil separator, which remove supply reservoir.
contaminants from the compressed air;
Supply Reservoir
S reservoirs, which store compressed air for various The supply reservoir delivers air to the primary service
systems; brake reservoir, the secondary service brake reservoir
and to the pressure protection valve, which in turn
delivers air to the remainder of the air system. The inlet
S air brake system valves, which control service,
port of the supply reservoir is protected by a one-way
parking and emergency brake functions;
check valve. The supply reservoir is located above and
forward of the tag axle, rear of the primary service
S axle end components, which convert air pressure to reservoir.
mechanical force for raking functions;
Primary Service Brake Reservoir
S suspension valving and air springs; The primary service brake reservoir supplies air to the
primary supply port of of the service brake valve, the
supply port of the R12-DC service brake relay valve (rear
S accessory system valving and components. brakes), and to the reservoir port of the SR-1 spring
brake valve. The supply port of the primary reservoir is
COMPONENTS protected by a one-way check valve. The primary
service brake reservoir is located above the drive axle,
Air Compressor
forward of the supply reservoir.
The air compressor is a two cylinder Bendix BA-921
located on the curbside of the engine below the Secondary Service Brake Reservoir
alternators. The air compressor is direct-driven from the The secondary service brake reservoir supplies air to
engine, and provides compressed air as required while the secondary supply port of the service brake valve.
the coach engine is running. Its air source is from the The supply port of this reservoir is protected by a
engine intake. Compressed air delivery is to the cooling one-way check valve. The inlet to the check valve is teed
coil upstream from the air dryer. to the low air pressure switch in the front junction box.
The secondary service brake reservoir is centered
Governor forward of the front axle.
The governor, which is mounted at the air dryer,
monitors air pressure in the accessory air system, Pressure Protection Valve
controls air compressor loading and unloading within a The pressure protection valve will allow air to pass
preset pressure range, and controls the purging of the through it only when the pressure at its supply port
air dryer. exceeds a predetermined pressure. In the event of a
large air leak downstream from the pressure protection
Cooling Coil valve, the air compressor can therefore maintain
The cooling coil lowers the temperature of the adequate air pressure in the service brake reservoirs. Air
compressor discharge air prior to its entering the air from the pressure protection valve is delivered to the the
dryer. This helps to optimize air dryer performance. The air manifold at the rear of the coach and the
cooling coil is located on the roadside tag axle bogie leg. suspension/accessory reservoir.

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 4A-3

Air Manifold R12-DC Service Brake Relay Valve (Rear

The air manifold delivers air to the emergency release Brakes)
reservoir, the rear suspension air system and the rear The R12-DC relay valve delivers air to the rear axle
accessory junction block. antilock braking system (ABS) valves and to the balance
port of the R14 park brake relay valve at a pressure
Emergency Release Reservoir
proportional to that delivered to its control ports by the
The emergency release reservoir provides an
service brake valve. Control air pressure is normally
independent source of compressed air to facilitate
received from both the primary and secondary portions
emergency release of the spring brakes when
of the service brake valve, but in the event of a failure of
insufficient air pressure is available in the service brake
either control line, the relay valve will still receive a
system. The supply port of this reservoir is protected by
control air signal and actuate the rear axle brakes
a one-way check valve. The emergency release
normally. The R12-DC air supply is directly from the
reservoir is centered forward of the drive axle.
adjacent primary service reservoir, allowing it to deliver
Suspension/Accessory Reservoir the large volumes of air required for actuation of the rear
The suspension/accessory reservoir supplies air to axle brake chambers. The R12-DC service brake relay
the front axle kneeling module, to the front accessory valve is located on the channel assembly above and to
junction block, and to the rear air manifold via the teed the rear of the drive axle.
connection at delivery port of the pressure protection
valve. The suspension/accessory reservoir is centered QR-1 Quick Release Valve (Front Brakes)
behind the front axle. The quick release valve delivers air to the front axle
Service Brake Valve antilock braking system (ABS) valves as received from
The service brake valve is actuated by the driver’s the secondary delivery port of the service brake valve
brake pedal and supplies modulated air pressure to the and, upon brake valve release, functions to speed air
service brakes in proportion to the level of brake pedal exhaust to minimize brake release times. The QR-1
application force. The primary portion of the brake valve quick release valve is mounted on the suspension
supplies air to the primary control port of the R12-DC reservoir to the rear of the front axle.
service brake relay valve (rear brakes) and to the primary
brake stoplight switch. The secondary portion of the Antilock Braking System (ABS) Valves
brake valve supplies air to the QR-1 quick release valve The ABS valves are normally open allowing service
(front brakes), the secondary control port of the R12-DC brake application air to pass through them to their
service brake relay valve (rear brakes), the control port of associated brake chambers. In the event that impending
the SR-1 spring brake valve, and to the secondary brake wheel lock-up is sensed by the ABS electronic controls,
stoplight switch. the ABS valves are electronically controlled to reduce
and modulate the delivery air to pressures that prevent
NOTE: The primary and secondary supply ports of
wheel lockup (other than momentary lockups) while
the service brake valve are teed to supply air to the
maximizing the braking effort available at the wheel(s)
primary and secondary air pressure transducers and
affected.
to each of the supply ports of the park brake supply
two-way check valve. The rear ABS valves are located on the coach frame
above the rear axles (two per axle). The front ABS valves
The service brake valve is located in the spare tire are mounted to the suspension reservoir to the rear of
compartment below the driver’s brake pedal. the front axle (one per side).

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 4A-4

Two-Way Check Valves SR-1 Spring Brake Control Valve

Two-way check valves receive supply air from two The SR-1 spring brake control valve is located on the
sources and deliver air to the next component in the channel assembly above and to the rear of the drive axle.
system from whichever of the two sources is at higher The SR-1 spring brake control valve serves two
pressure. For example, the park brake valve two-way functions.
check receives air from the primary and secondary 1. Park Brake Control: Under normal operating
service brake supplies at the service brake valve and conditions the SR-1 spring brake control valve
delivers air to the park brake valve supply port from delivers air at a regulated air pressure to the park
whichever of those two systems is at a higher pressure at brake relay valve control port (park brakes
any given time. released) when the PP-1 park brake valve is
depressed or exhausts air from the park brake relay
Two-Way Check Valve (Park Brake Valve valve control port (park brakes applied) when the
Supply) PP-1 park brake valve is pulled.
The two-way check valve (park brake valve supply) 2. Emergency Brake Control: The SR-1 spring brake
receives air from the primary and secondary service control valve has a reservoir port that monitors the
brake supplies at the service brake valve and delivers it air pressure available in the primary service brake
to the supply port of the PP-1 park brake valve. reservoir and a control port that receives delivery air
from the secondary portion of the service brake
PP-1 Park Brake Valve valve. When the SR-1 valve senses that the primary
When the park brake valve button is depressed (park reservoir air pressure has dropped to a
brakes released position), the PP-1 park brake valve predetermined level, it will control the air pressure
delivers air to the exhaust port of the RD-3 emergency being delivered to the park brake relay valve control
release valve. When the park brake valve button is pulled port and allow modulated application of the park
(park brakes applied position), the park brake valve brakes in proportion to secondary service brake
exhausts air from the RD-3 emergency release valve. application pressures. The higher the secondary
Under normal operating conditions, this valve remains in service application pressure, the lower the air
the park brakes released or park brakes applied position pressure to the park brake relay valve, and the
as chosen by the driver. In the event that both service higher the spring brake spring force applied to the
brake air supplies drop below approximately 45 psi, the rear brakes.
park brake valve will automatically shift to the applied
position, at which point the park brakes cannot be Two-Way Check Valve (Park Brake Relay Valve)
released using this valve. This function can be tested by The two-way check valve supplies are from the
repeatedly applying and releasing the service brakes two-way check valve that supplies the PP-1 park brake
with the coach engine not running. The PP-1 park brake valve and from the emergency release reservoir. The
valve is located towards the front of the driver’s left-hand delivery port is plumbed directly to the park brake relay
console. valve. The park brake relay valve two-way check valve is
located on the R14 park brake valve supply port.
RD-3 Emergency Release Valve
The RD-3 emergency release valve receives air at its R14 Park Brake Relay Valve (Rear Brakes)
supply port from the emergency release reservoir, but is The R14 park brake relay valve delivers air to the
a normally open valve that allows air to pass freely spring ports on the rear axle spring brake chamber
between its exhaust and delivery ports and thus spring ports at a pressure proportional to that received at
between the delivery port of the PP-1 park brake valve its control port from the SR-1 spring brake control valve.
and the supply port of the SR-1 spring brake control The R14 park brake relay valve is active in both the park
valve. In the event of an automatic application of the park brake and emergency brake modes. In the event that the
brake valve due to a loss of service brake air pressure, spring brakes are in the applied state and a service
and the coach must be moved to a safe location, the brake application is made, rear service brake air from the
emergency release valve button can be pushed and service brake relay valve delivery is supplied to the park
held, delivering air pressure from the emergency release brake relay valve balance port. This causes the park
reservoir to the SR-1 spring brake control valve and brake relay valve to apply air to the spring port of the
releasing the park brakes. Sufficient air should be spring brake chambers to provide anti-compounding,
available to allow for a minimum of three releases and preventing simultaneous application of service brake
reapplications. The RD-3 emergency release valve is and parking brake forces on the brake assembly
located toward the rear of the driver’s left-hand console. components.

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 4A-5

Brake Chambers (Rear Brakes) Front Accessory Junction Block

Brake chambers on the rear axles are of the spring The front accessory junction block air supply comes
brake type and provide for service brake, park brake, from the suspension/accessory reservoir and it delivers
and emergency brake functions. For the service brake air to the entrance door control dump valve and the air
function, service brake air pressure delivered to the horn electric solenoid valve which controls sounding of
service port acts upon the service diaphragm which, the air horn. The front accessory junction block is
based on its area and the air pressure applied, provides located on the rear wall of the spare tire compartment.
force to the brake chamber pushrod, which in turn acts
upon the brake assembly lever. For the park brake Entrance Door Control Dump Valve
function, a large internal spring applies force to the park
The entrance door control dump valve, when
brake piston which in turn transmits this force to the
actuated, blocks the air supply to and exhausts air from
pushrod and on to the brake assembly lever. Park brake
the entrance door control module allowing the entrance
air pressure supplied to the spring port acts under the
door to be opened or closed manually.
park brake piston compressing the internal spring and
releasing the park brakes. For the emergency brake
function, modulated air pressure is applied under the
Entrance Door Control Module
park brake piston to modulate brake application forces. The entrance door control module is actuated by the
The rear brake chambers are located at the wheel ends entrance door switch in the driver’s area and delivers
of the drive and tag axles. sequenced air to the entrance door control and lock
cylinders to facilitate opening, closing and locking of the
entrance door.
WARNING
Rear Accessory Junction Block
Spring brake chambers contain a great deal The rear accessory junction block air supply comes
of potential energy. Use extreme caution from the suspension/accessory reservoir (teed at the
when servicing the chamber. Do not work on pressure protection valve delivery port ) and it delivers air
the chamber without first caging the spring. to the engine cooling fan circuit (in-line filter, electric
Do not try to disassemble the spring portion solenoid valve and fan clutch), the coolant bypass valve
under any circumstance. If damage to the in the engine compartment, the reservoir port of the air
chamber cage is detected or suspected, re-
compressor governor, the B500R or Autoshift
move and replace the chamber.
transmission (if so equipped) and the lavatory
Spring brake chambers cannot be disposed compartment flush circuit. The rear accessory junction
of in the normal way. Sever corrosion at a block is located on the frame cross member between the
landfill site can allow the spring to suddenly tag axle bogie legs.
escape and cause severe personal injury or
death. The spring chambers must be prop- Low Air Pressure Switch
erly disarmed using special equipment and
procedures before disposal. The low air pressure switch monitors the supply
reservoir air pressure as received at the secondary
brake reservoir and causes the “Supply Air Low”
Brake Chambers (Front Brakes) indicator on the instrument panel to light and the low air
Brake chambers on the front axle are single buzzer to sound when the supply reservoir pressure
diaphragm type. Service brake air pressure delivered to drops below approximately 75 psi. Note that when air
the service port acts upon the service diaphragm which, pressure is building in the supply reservoir after a low air
based on its area and the air pressure applied, provides situation, the light and buzzer will remain activated until
force to the brake chamber pushrod, which in turn acts air pressure reaches approximately 100 psi. The low air
upon the brake assembly lever. Front brake chambers pressure switch is located in the front electrical junction
are located at the wheel ends of the front axle. box.

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 4A-6

Service Reservoir Pressure Transducers System Air Fill Provision

The service reservoir pressure transducers monitor
The system air fill provision consists of a standard
the pressures in the primary and secondary service
quick disconnect fitting and a one-way check valve that
brake reservoirs as received at the service brake valve
allow for filling of the entire air system. Compressed air
supply ports. They drive the primary and secondary air
that is added through this fitting enters the system
pressure gauges on the driver’s instrument panel as well
upstream from the cooling coil and air dryer and is
as the low air pressure indicators on the faces of these
therefore dried and filtered before entering the
gauges. The low pressure indicators will illuminate when
remainder of the air system. The system air fill provision
air pressure drops below approximately 75 psi in their
is located at the rear of the engine compartment, on the
respective reservoirs. Because a low air condition in
right-hand side.
either service reservoir will also draw down the air
pressure in the supply reservoir, the low air indicator and
low air buzzer associated with that reservoir will also Emergency Air Fill Provisions
activate. The service reservoir pressure transducers are
located in the front electrical junction box. The emergency air fill provisions consist of standard
quick disconnect fittings, each with its own one-way
Stop Lamp Switches (Service and Park check valve, that allow for filling of the primary and
Brakes) secondary air reservoirs and the park brake system.
The service brake stop lamp switches (2) receive air Compressed air that is added through these fittings
delivered from the service brake valve primary and enters the system at the supply ports of the two-way
secondary delivery ports and, when pressurized, cause check valve (park brake valve supply) and is therefore
the stop lamps on the rear of the coach to light. The park not dried or filtered before entering the service brake
brake stop lamp switch receives air delivered from the reservoirs and park brake system. Because of the
PP-1 park brake valve delivery port and, when air is potential for contaminated air being introduced into the
exhausted (park brakes applied), causes the stop lamps coach air system when using these provisions, they
on the rear of the coach to light. The stop lamp switches should be used only in emergency situations. The
are in the front electrical junction box. emergency air fill provisions are located on the left-hand
Primary and Secondary Service Brake front side service compartment.
Systems
The service brakes consist of two separate systems:
the primary service brake system which actuates the
Towing Provisions
drive and tag axle brakes and the secondary service The towing provisions allow for a towing vehicle,
brake system which actuates the front axle brakes. The when correctly connected, to release the park brakes,
two systems are balanced to provide for minimal maintain primary service reservoir air pressure, and
stopping distances with each axle contributing in modulate the primary (rear) brakes in tandem with those
accordance with its load-carrying capacity. In the event of the towing vehicle. The connection labeled “Supply”
of a failure in the secondary (front) service brake system, will deliver air both to the exhaust port of the PP-1 park
the primary (rear) service brakes will maintain excellent brake valve to allow the park brakes to be released and
emergency stopping capacity approximately in to the primary service brake reservoir to provide the
proportion to the high percentage of the coach weight R-12DC service brake relay valve with a high volume air
which they carry. In the event of a failure in the primary source at its supply port. The second connection,
(rear) service brake system, the SR-1 spring brake labeled “Service,” will deliver air via a two-way check
control valve will modulate the rear axle spring brake valve to the primary control line of the R-12DC, allowing
chambers in accordance with secondary service brake the primary (rear) brakes to be controlled by the towing
application pressures to maintain an excellent vehicle. The towing provisions are located in the
emergency stopping capacity. left-hand front side service compartment.

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 4A-7

Connections to The Towing Vehicle

The towing provision ports are fitted with 1/4” NPT
muffler fittings that must be replaced with fittings
WARNING
provided by the towing vehicle’s operator or optionally
with the quick disconnect fittings that can be removed 1. Park the coach on a level surface, apply the
from the adjacent emergency fill provision ports. The park brake and block the wheels.
spare tire door (front bumper) should be opened to allow 2. Turn the engine off. If the engine must be
routing of the towing vehicle’s hoses between the two running, use EXTREME CAUTION to avoid
vehicles. The hoses should then be aligned with the personal injury.
opening provided in the top of the bumper just below the 3. Switch the main battery disconnect OFF.
roadside license plate, and the bumper should be 4. Vent all reservoirs.
closed. The sequence of hooking up to the coach should 5. Wear safety glasses.
follow that for hooking up to a semi-trailer, with the
6. Do not connect or disconnect pressurized
connecting of the hoses being the last operation. When
lines.
the towing vehicle’s supply (sometimes called
emergency) hose is connected to the port labeled 7. Ensure that system pressure has been de-
“Supply,” the park brakes will be released and the pleted before removing components.
primary (rear) service reservoir will be filled. When the 8. Never exceed recommended pressures.
“Service” hose is connected, the towing vehicle will be 9. Do not install, remove, disassemble or as-
able to control the primary service brakes in tandem with semble a component until you have read
its own service brakes. and understood the procedure.
The PP-1 park brake valve must be left in the “applied” 10. Use proper tools and follow precautions
or “up” position (see Breakaway Protection) throughout pertaining to their use.
the towing procedure. Any fittings that were removed to 11. Use vendor replacement parts. Replace-
accommodate towing must be reinstalled in their ment hardware must be equivalent to the
original locations when towing is complete, otherwise original.
the coach braking system integrity and/or operability
12. Components that have stripped threads or
could be severely impaired. The use of the towing
damaged parts must be replaced, not re-
provisions is possible only if the park brake and primary
paired. DO NOT machine or weld parts un-
service brake air circuits are intact.
less approved by the manufacturer.
Breakaway Protection 13. Before returning the coach to service, en-
In the event that the supply hose connection is sure that components and systems are re-
severed, air pressure will be lost at the exhaust port of stored to operating condition.
the PP-1 park brake valve and the park brakes will apply
automatically.

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 4B-1

SECTION 4B
AIR COMPRESSOR AND GOVERNOR
CONTENTS OF THIS SECTION
SUBJECT PAGE
Air Compressor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B-2
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B-2
Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B-2
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B-3
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B-4
Inspections and Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B-4
Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B-6
Disassembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B-6
Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B-7
System Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B-8
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B-10
Governor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B-13
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B-13
Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B-13
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B-13
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B-14
Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B-14
Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B-14
Removal and Disassembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B-15
Assembly and Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B-16
Torque Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B-17
Compressor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B-17
Governor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B-17
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B-18
Compressor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B-18
Governor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B-18

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 4B-2

AIR COMPRESSOR
GENERAL DESCRIPTION

The Bendix BA-921Rair compressor is a single UNLOADER COOLANT IN OR OUT

COVER (ONE OR OTHER NOT USED)
cylinder, reciprocating compressor with a rated
BOLT HED (4)
displacement of 15.8 CFM at 1250 RPM (Figure 1). The
compressor is mounted to and driven directly by the
engine front auxiliary drive. The compressor is water
GOVERNOR
cooled, and filtered air from the engine intake manifold INLET CONNECTION
PORT
flows to the compressor through a separate intake tube
or hose. DISCHARGE
PORT
The compressor provides and automatically
maintains air pressure to the air dryer through a
governor controlled loading and unloading mechanism. DISCHARGE
COOLANT IN OR OUT SAFETY VALVE
The air compressor operates continuously while the (ONE OR OTHER NOT USED)
engine runs, but actual compression is controlled by the
intake valve unloader piston arrangement. The
unloaders are actuated by governor control air. 4436 Figure 2. Cylinder Head
NOTE: The air compressor and governor work in
The governor operates in conjunction with the air
conjunction with the air dryer to keep system
compressor inlet valve unloader mechanism to
pressure maintained. The air dryer control port is
automatically provide pressurized air to the dryer and
pressurized by the governor.
the entire air system. Predetermined maximum (unload)
and minimum (load-up) set pressures are adjustable.
COMPONENTS
The governors are mounted to the air compressor on all
The compressor installation consists of three major
engine installations.
components: the cylinder head, crankcase housing and
the governor assembly.
Cylinder head
The cylinder head houses the intake, discharge, and
intake unloader valving. The cylinder head is bolted to
the compressor housing. The cylinder head provides for
reservoir, unloader and exhaust port mounting to the
governor. The coolant water inlet port is connected to the
engine block, and the coolant return is connected to the
engine cylinder head. The air intake port is connected to
the intake air tube or hose from either the filter or
manifold. The discharge port is connected to the
discharge air line (Figure 2).
Crankcase
The crankcase houses the cylinder bore, piston,
crankshaft and main bearings, and provides the flange
or base mounting surface for cylinder head. A
nameplate identifying the compressor part number and
serial number is attached to the side of the crankcase.

NOTE: The crankcase drive housings may differ

4435 Figure 1. Bendix BA-921R Air Compressor depending on the engine installation.

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 4B-3

OPERATIONAIR
Loaded AIR INLET
PORT
During the down stroke of the piston, a slight vacuum
is created between the top of the piston and the cylinder DISCHARGE
VALVE OPEN
head, causing the inlet valve to move off its seat and AIR
open. Air is drawn through the open valve into the DISCHARGE
PORT
cylinder. The discharge valve remains on its seat during UNLOADER
intake valve operation (Figure 3). PORT
VALVE
PLATE

AIR INLET DISCHARGE UNLOADER

PORT VALVE CLOSED PISTON
AIR DOWN &
DISCHARGE SEATED
PORT UNLOADER INLET VALVE
PORT CLOSED

VALVE PLATE PISTON MOVING UP

UNLOADER
INLET PISTON 5045 Figure 4. Operation - Loaded (Compression)
VALVE DOWN &
OPEN SEATED
Unloaded
When the air pressure in the supply reservoir reaches
the cut-out setting of the governor, the governor delivers
system air to the compressor unloader port. Air entering
the unloader port acts on the unloader piston causing it
to move away from its seat on the valve plate assembly.
When the unloader piston is unseated a passage is
5045 Figure 3. Operation - Loaded (Intake) opened between the cylinder bore and the air inlet cavity
As the piston begins its upward stroke, the inlet valve in the cylinder head. Air compression ceases (Figure 5).
is seated to allow air that was drawn into the cylinder to As the piston moves from bottom dead center (BDC)
be compressed. The piston continues the upward to top dead center (TDC) air in the cylinder bore flows
stroke and compressed air pushes the discharge valve past the unseated unloader piston, into the cylinder
open, as compressed air escapes into the inlet valve of head inlet cavity and out the inlet port. On the piston
the discharge line (Figure 4). down stroke (TDC to BDC) air flows in the reverse
As the piston reaches the top of its stroke and starts direction, from the inlet cavity past the unseated
down, the discharge valve spring and air pressure in the unloader piston and into the cylinder bore.
discharge line returns the discharge valve to its seat.
This prevents the compressed air in the discharge line AIR INLET DISCHARGE VALVE
from returning to the cylinder bore as the intake and PORT CLOSED
compression cycle is repeated AIR
DISCHARGE
NOTE: During loaded operations the governor PORT
exhaust port is open to the unloader port, thereby AIR FROM
exhausting air from the unloader mechanism and GOVERNOR
VALVE UNLOADER
the dryer control line. PLATE PORT

UNLOADER
PISTON UP
&
INLET UNSEATED
VALVE
CLOSED
PISTON MOVES
UP & DOWN

5048 Figure 5. Operation - Unloaded

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 4B-4

MAINTENANCE 10. Components with stripped threads or damaged

parts should be replaced rather than repaired.
Repairs requiring machining or welding should
not be attempted unless specifically approved
WARNING and stated by the coach or component
manufacturer.
11. Prior to returning the coach to service, make
When working on the coach compressor, certain all components and systems are
the following general precautions
restored to their proper operating condition.
should be observed:
INSPECTIONS AND TESTS
Operational and Leakage Tests
1. Park the coach on a level surface, apply the
Every 50,000 miles (80,000 km) or 1,500 operating
parking brakes, and always block the wheels.
hours perform the “Operational and Leakage” tests. The
2. Make certain to drain the air pressure from all compressor must be capable of raising system air
reservoirs before beginning any work on the pressure from 85 psi to 100 psi in 25 seconds or less.
coach. This test is performed with the engine at maximum
3. Disconnect the batteries at the switches in the governed speed with minimum required reservoir
battery compartment. capacity (FMVSS 121).
4. Always wear safety glasses. COMPRESSOR LEAKAGE CHECK
5. When working in the engine compartment the Compressor leakage tests need not be performed on
engine should be shut off. Where circumstances a regular basis. These tests should be performed when
require that the engine be in operation, extreme discharge valve leakage is substantially affecting
caution should be used to prevent personal compressor performance, or when it is suspected that
injury resulting from contact with moving, the compressor is “cycling” between the load and
rotating, leaking, heated, or electrically charged unloaded modes due to unloader piston leakage.
components. NOTE: The following tests must be performed with
6. Never connect or disconnect a hose or line the coach parked on level surface, engine off and
containing pressure; it may whip. Never remove the entire air system completely drained.
a component or plug unless you are certain all The unloader pistons can be checked for leakage as
system pressure has been depleted. follows: With the cylinder head removed from the
7. Never exceed recommended pressures. compressor and the inlet flange securely covered, apply
8. Do not attempt to install, remove, disassemble 120 psi of air pressure to the governor port. Listen for an
or assemble a component until you have read escape of air at the inlet valve area. An audible escape of
and thoroughly understand the recommended air should not be detected. Any unloader piston leakage
procedures. Use only the proper tools and must be repaired before this test is performed.
observe all precautions pertaining to use of Leakage past the discharge valves can be detected
those tools. as follows: remove the discharge line and apply shop air
back through the discharge port. Listen for an escape of
9. Use only vendor replacement parts,
air at the compressor inlet cavity. A barely audible
components, or repair kits. Replacement
escape of air is generally acceptable.
hardware, tubing, hose, fittings, etc. should be
of equivalent size, type, and strength as original NOTE: If the compressor does not function as
equipment and be designed specifically for described above or if the leakage is excessive,
such applications and systems. repair and retest.

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 4B-5

Compressor Lubrication flow in all external oil supply and return lines should be
The coach engine provides a continuous supply of oil made. Supply lines must be a minimum of 3/16 inch I.D.
to the compressor. Oil is routed from the engine to the and return lines must be a minimum of 1/2 inch I.D. Oil
compressor oil inlet. An oil passage in the compressor return lines should slope as sharply as possible back to
crankshaft allows oil to lubricate the connecting rod the engine crankcase and should have as few fittings
crankshaft bearings (Figure 6). Connecting rod wrist pin and bends as possible. Refer to the tabulated technical
bushings and crankshaft ball bearings are spray data in the back of this section for oil pressure minimum
lubricated. The oil drains back directly to the engine values.
through the mounting flange.
Compressor Air Intake
Every 5,000 miles (8,000 km) or 150 operating hours
or when the engine intake air filter is changed, the
compressor intake tube and adapters should be
OIL INLET
checked. Check the tube for deterioration or damage
and check the clamps to be sure they are secure.
Inspect both adapters for cracks and damage. Replace
any damaged parts.

Compressor Cooling
OIL
OUTLET Air flowing through the engine compartment from the
action of the engine fan and the movement of the coach
4469
assists in cooling the compressor. Coolant flowing from
the engine cooling system through connecting lines
enters the head and passes through internal passages
4469 Figure 6. Lubrication in the cylinder head and is returned to the engine
(Figure 7). Proper cooling is important in maintaining
discharge air temperatures below the maximum
recommended 400)F.
Every 50,000 miles (80,000 km) or 1,500 operating
hours inspect the compressor discharge port, inlet
cavity and discharge line for evidence of restrictions and
carboning. If excessive buildup is noted, thoroughly
clean or replace the affected parts and closely inspect
the compressor cooling system. Check all compressor
coolant lines for kinks and restrictions to flow. Minimum
coolant line size is 3/8 inch I.D. Check coolant lines for
internal clogging from rust scale. If coolant lines appear
suspicious, check the coolant flow and compare to the
specifications at the end of this section.
Compressor Drive
Every 50,000 miles (80,000 km) or 1,500 operating
hours check for noisy compressor operation, which
4471 Figure 7. Cooling could indicate a worn drive gear coupling, or excessive
NOTE: The intervals listed pertain to typical internal wear. Adjust and/or replace as necessary.
highway operations. More frequent maintenance Check all compressor mounting bolt torques. Every
will be required for operation in off-highway and/or 200,000 miles (322,000 km) or 6,000 operating hours
urban environments. remove, disassemble, clean and inspect all the
compressor parts thoroughly. Replace all worn or
Every 50,000 miles (80,000 km) or 1,500 operating damaged parts or replace the compressor with a
hours an inspection for kinks, bends, or restrictions to remanufactured unit.

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 4B-6

COMPRESSOR REMOVAL 8. Reinstall the compressor in the reverse order of the

These instructions are general and are intended as a removal steps.
guide. Additional preparations and precautions may be NOTE: The following “Disassembly” and
necessary. “Assembly” procedures is presented for reference
1. Turn the battery disconnect OFF. Block the wheels purposes and presupposes that a major rebuild of
and vent the entire air system. the compressor is being undertaken.
2. Drain the engine cooling system and the
compressor cylinder head. Identify and disconnect DISASSEMBLY
all air, water and oil lines leading to the compressor. Remove the balance of road dirt and grease from the
3. Remove the governor and support brackets. See exterior of the compressor with a cleaning solvent. Mark
Governor Removal in this section. the rear end cover or end cover adapter in relation to the
4. Match-mark the mounting flange to the engine front crank case. It is recommended but not specifically
gear case for proper orientation at reinstallation. necessary to mark the relationship of the cylinder head
to the valve plate assembly and crankcase and cylinder
5. Remove the discharge and inlet fittings and note block assembly.
their positions on the compressor.
A convenient method to indicate the above
6. Remove the flange mounting bolts and remove the relationship is to use a metal scribe to mark the parts
compressor from the coach. with numbers or lines. Do not use marking methods
7. Remove the drive gear from the compressor such as chalk that can be wiped off or obliterated during
crankshaft with a gear puller. rebuilding.
8. Inspect the gear and associated parts for visible Prior to disassembly make certain that the
wear or damage. Replace if worn or damaged. appropriate kits and /or replacement parts are available.
Refer to figure during the entire disassembly procedure.
NOTE: The following disassembly and assembly Cylinder Head
procedures are presented for reference and 1. Remove the discharge safety valve from the
presuppose that a major rebuild of the compressor is cylinder head.
being undertaken.
2. to restrain the spring force exerted by balance
piston spring, hold the unloader cover in place
These instructions are general and are intended to be while removing the two unloader cover cap screws.
a guide, in some cases additional preparations and Carefully release the hold on the unloader cover
precautions are necessary. until the spring force is relaxed, then remove the
1. Turn the battery disconnect to “Off”. Block the unloader cover.
wheels of the coach and vent the entire air system. 3. Remove the unloader cover gasket.
2. Drain the engine cooling system and the cylinder 4. Remove the balance piston and its spring from the
head of the compressor. Identify and disconnect all cylinder head.
air, water and oil lines leading to the compressor. 5. Remove the four hex head bolts and washers from
3. Remove the governor and any support brackets. the cylinder head.
Use the previous “Governor Disassembly” 6.
procedure. 7. Gently tap the head and valve plate assembly with a
4. Match mark mounting flange to engine front gear soft mallet to break the gasket seal. Lift the cylinder
case for proper orientation at reinstallation. head and valve plate assembly off the cylinder
5. Remove the discharge and inlet fittings and note block.
their positions on the compressor to aid in 8. Remove the metal reed valve/gasket.
assembly. 9. Gently tap the head and valve plate assembly with a
6. Remove the flange mounting bolts and remove the soft mallet to break the gasket seal. Then separate
compressor from the coach. the cylinder head from the valve plate assembly and
remove the gasket.
7. Remove the drive gear from the compressor
10. Turn the aluminum cylinder head over to expose
crankshaft using a gear puller. Inspect the gear and
the interior portion of the head. Push the unloader
associated parts for visible wear or damage. Since
piston along with its o-rings out of the cylinder head.
these parts are precision fitted, they must be
replaced if they are worn or damaged. Crankcase Cover

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 4B-7

1. Remove the four crankcase cover cap screws 3. Inspect the cylinder head for cracks or damage.
securing the crankcase cover to the crankcase. With the cylinder head and head gasket secured to
Using a soft mallet, gently tap the crankcase cover the valve plate assembly, apply shop air pressure to
to break the gasket seal. Remove the crankcase one of the coolant ports with all others plugged, and
cover gasket. check for leakage by applying a soap solution to the
exterior of the head. If leakage is detected ted in the
Rear End Cover or End Cover Adapter cylinder head casting, replace the compressor.
1. Remove the four end cover cap screws that secure
the rear end cover or end cover adapter to the Cylinder Block
crankcase. 1. Check the cylinder head gasket surface on the
cylinder block for nicks, gouges and marring. A
2. Remove the rear end cover or end cover adapter
metal gasket is used to seal the cylinder head to the
from the crankcase. Remove the o-ring seal from
cylinder bock. This surface must be smooth and
the end cover.
free of all but the most minor scratching. If
excessive marring or gouging is detected, the
CLEANING OF PARTS
compressor must be replaced.
General
COMPRESSOR ASSEMBLY
All parts should be cleaned in a good commercial General Note: All torques specified in this section are
grade of solvent and dried prior to inspection. assembly torques and typically can be expected to fall
Cylinder Head off after assembly is accomplished. Do not re-torque
1. Carefully remove all gasket material adhering to the after initial assembly torques fall unless instructed
aluminum cylinder head, steel valve plate assembly otherwise. a complied listing of torque specifications is
and cast iron cylinder block. Make certain not to presented at the end of the section.
deeply scratch or mar the gasket surfaces. Pay Crankcase Cover
particular attention to the gasket surfaces of the 1. Position the crankcase cover gasket on either the
aluminum head. crankcase or crankcase cover and install the
2. Remove carbon deposits from the discharge and crankcase cover on the crankcase using the four
inlet cavities of the cylinder head and valve plate cap screws. “Snug” the four cap screws then
assembly. They must be open and clear in both torque to 62-71 inch pounds using a crossing
assemblies. Make certain not to damage the pattern.
aluminum head. Crankcase End Cover or Adapter
3. Remove rust and scale from the cooling cavities and 1. Install the end cover o-ring on the crankcase end
passages in the head and valve plate assembly and cover.
use shop air to clear debris from the passages. 2. Orient the crankcase end cover or end cover
4. Check the threads in all cylinder head ports for adapter to the crankcase using the reference marks
galling. Minor chasing is permitted. made during disassembly. Carefully install the end
5. Make certain the unloader vent passage under the cover or end cover adapter in the crankcase
unloader cover in the head is open and free of making certain not to damage the crankshaft
debris. bearing surface in it.
3. Install the four end cover screws or studs. “Snug”
INSPECTION OF PARTS the screws then tighten to 195 to 213 inch pounds
Cylinder Head & Valve Plate using a crossing pattern.
1. Carefully inspect the cylinder head gasket surfaces Cylinder Head
for deep gouges and nicks. If detected, the 1. Note the position of the protruding alignment pins
compressor must be replaced. on the cylinder block. Install the metal inlet reed
2. Carefully inspect the valve plate assembly gasket valve/gasket over the alignment pins on the
surfaces for deep gouges and nicks. Pay particular cylinder block.
attention to the metal gasket surface. a metal 2. Position the valve plate assembly on the cylinder
gasket is used between the valve plate assembly block so that the alignment pins in the cylinder
and cylinder block. This surface must be smooth block fit into the corresponding holes in the valve
and free of all but the most minor scratching. If plate assembly.
excessive marring or gouging is detected, the 3. Position and install the metal gasket over the
compressor must be replaced. alignment bushings protruding from the valve plate

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 4B-8

assembly. When properly installed, the outline of 4. Install the discharge, inlet and governor adapter
the gasket matches the outline of the valve plate. fittings, if applicable, in the same position on the
4. Position and install the cylinder head over the compressor noted and marked during
alignment bushings protruding from the valve plate disassembly. Make certain the threads are clean
assembly. and the fittings are free of corrosion. Replace as
necessary.
NOTE: The alignment bushings will only fit into two 5. Inspect all air, oil and coolant lines and fittings
of the four cylinder head bolt holes. before reconnecting them to the compressor. Make
certain o-ring seals are in good or new condition.
5. Install the four hex head cylinder head bolts and Tighten all hose clamps.
washers and snug them, then tighten evenly to a
6. Clean oil supply line. Before connecting this line to
torque of 265 to 292 inch pounds using a crossing
the compressor. Run the engine briefly to be sure oil
pattern.
is flowing freely through the supply line.
6. Install the unloader piston with its pre-installed
7. Before returning the coach to service, perform the
o-rings in the cylinder head marking certain not to
Operation and Leakage Tests specified in the
damage them in the process.
section. Pay particular attention to all lines
7. Install the balance piston spring in the unloader reconnected during installation and check for air, oil
piston, then install the small diameter of the balance and coolant leaks at compressor connections. Also
piston through the center of the spring. check for noisy operation.
8. Install the unloader cover gasket on the cylinder
head making certain the unloader vent passage COMPRESSOR SYSTEM CHECK
and both screw holes align. Testing Rebuilt Compressor
9. Position the unloader cover on top of the balance In order to properly test a compressor under
piston making certain the stamped logo is visible. operating conditions, a test rack for correct mounting,
10. Press and hold the unloader cover in place on the cooling, lubricating, and driving the compressor is
cylinder head and install both unloader cover cap necessary. Such tests are not compulsory if the unit has
screws. Torque the cover cap screws to 62 to 71 been carefully rebuilt by an experienced mechanic. A
inch pounds. compressor efficiency or build up test can be run which
Installing the Compressor is not too difficult. An engine lubricated compressor
must be connected to an oil supply line of at least 15 psi.
1. If the compressor was removed for replacement, pressure during the test and an oil return line must be
install the drive components. Torque the installed to keep the crankcase drained. Connect to the
crankshaft nut to 250 foot pounds. compressor discharge port, a reservoir with a volume of
2. Install any supporting bracketing on the 1500 cubic inches, including the volume of the
compressor in the same position noted and marked connecting line. With the compressor operating at 2100
during removal. RPM., the time required to raise the reservoir(s) pressure
3. Install the gasket on the drive flange of the from 85 psi to 100 psi should not exceed 5 seconds.
compressor. Make certain oil supply or return holes During this test, the compressor should be checked for
in the gasket are properly aligned with the gasket leakage and noisy operation, as well as unloader
compressor and engine. Gasket sealants are not operation and leakage. If the compressor functions as
recommended. Secure the compressor on the indicated reinstall on the coach connecting all lines as
engine and tighten the mounting bolts. marked in the disassembly procedure.

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 4B-9

SAFETY VALVE

UNLOADER COVER CAP SCREW

UNLOADER COVER

CYLINDER HEAD GASKET

UNLOADER CAP

UNLOADER BALANCE PISTON

SPRING
HEAD GASKET
O-RING
UNLOADER PISTON

VALVE PLATE ASSEMBY

O-RING
O-RING

INLET REED VALVE/GASKET

CRANKCASE
&
CYLINDER
BLOCK

O-RING

BOTTOM COVER GASKET

END COVER
BOTTOM COVER

4410 Figure 8. BA-921 Air Compressor

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 4B-10

COMPRESSOR TROUBLESHOOTING
Condition Cause Correction
1. Compressor passes 1.A. Restricted air in- 1.A.1. Check the engine or compressor air cleaner and re-
too much oil (oil at take. place if necessary.
valving exhaust 1.A.2. Check the compressor air inlet for kinks, or exces-
ports or seeping sive bends and be certain the inlet lines have the mini-
from the air mum specified inside diameter of 5/8 inch. The recom-
strainer). mended maximum air inlet restriction is 25 inches of wa-
ter.
1.B. Restricted oil re- 1.B.1. Make certain oil drain passages in the compressor
turn. and mating engine surfaces are aligned and not ob-
structed. Take special care when using sealants with or
instead of gaskets.
1.B.2. Oil return to the engine should bot be in any way re-
stricted. Check for excessive bends, kinks and restric-
tions in the oil return line. Minimum recommended oil
return line size is 5/8 inch O.D. tubing or equivalent I.D.
(1/2 inch minimum). Return line must consistenely de-
scend from the compressor to the engine crankcase.
1.C. Poorly filtered inlet 1.C.1. Check for a damaged, defective or dirty air filter on
air. engine or compressor.
1.C.2. Check for leaking, damaged or defective compressor
air intake components (i.e., induction line, fittings,
gaskets, filter bodies, etc.).
1.C.3. The compressor intake should not be connected to
any part of the exhaust gas recirculation system on the
engine.
1.D. Insufficient 1.D.1. Remove accumulated grease, grime or dirt from the
compressor cooling cooling fins. Replace components found damaged.
(compressor runs Check for damaged cooling fins. Replace components
hot). found damaged.
1.E. Contaminants not 1.E.1. Check the reservoir drain valves to ensure that they
regularly drained are functioning properly.
from reservoirs.
1.F. Compressor runs 1.F.1. System leakage should not exceed 1 psi pressure
loaded for an drop per minute without the brakes applied, and 3 psi
excessive time. pressure drop per minute with brakes applied. If leakage
is excessive, check for system leaks and repair them.
1.G. Excessive engine 1.G.1. Test for excessive engine crankcase pressure and
crankcase pressure. replace or repair ventilation components as necessary.
(An indication of crankcase pressure is a loose or
partially lifted dipstick.)
1.H. Excessive engine 1.H.1. Check the engine oil pressure with a test gauge and
oil pressure. compare the reading to the engine specifications. Bendix
does not recommend restricting the compressor oil
supply line, because of the possibility of plugging the
restriction with oil contaminants. The minimum oil supply
line size is 3/8 inch I.D. tubing.
1.I. Faulty compressor. 1.I.1. Replace or repair the compressor only after making
certain none of the preceding installation defects exist.

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Printed in Canada.
 Date March 2003 Page 4B-11

2. Noisy compressor 2.A. Loose drive gear. 2.A.1. Inspect the drive gear fit on the compressor
operations. crankshaft. The gear must be completely seated and the
crankshaft nut must be tight.
A damaged crankshaft surface or keyway is an indication
of loose drive components. If damage to the compressor
crankshaft is detected, replace the compressor.
When installing the drive gear, torque the crankshaft nut
to the appropriate torque specifications. DO NOT back
off the crankshaft nut to align the cotter pin and
castellated nut. (Some compressors do not use
castellated nuts.) DO NOT USE IMPACT WRENCHES.
2.B. Excessively worn 2.B.1. Inspect the drive gear and couplings and engine for
drive couplings or excessive wear. Replace as necessary. (Replace
gears. nonmetallic gears when changing the compressor.)
2.C. Compressor 2.C.1. Inspect the compressor discharge port and discharge
cylinder head or line for carbon buildup. If carbon is detected, check for
discharge line proper cooling to the compressor. (See #1D.)
restrictions. Inspect the discharge line for kinks and restrictions.
Replace the discharge line if necessary.
2.D. Poorly filtered inlet 2.D.1. Check oil pressure in the compressor. The minimum
air. required oil pressure is 15 psi with the engine idling, and 15
psi at maximum governed engine rpm. Check for excessive
oil temperature - it should not exceed 240_F.
2.E. Faulty compressor. 2.E.1. Replace or repair the compressor after determining
none of the preceding installation defects exist.
3. Excessive buildup 3.A. Dirty induction air 3.A.1. Inspect the engine or compressor air filter and
and recover time. filter. replace if necessary.
Th compressor
The
3.B. Restricted 3.B.1. Inspect the compressor air induction line for kinks
should be able to
induction line. and restrictions and replace it as needed.
build air system
from 0-125 psi in 3 3.C. Restricted 3.C.1. Inspect the compressor discharge port and line for
minutes with engine discharge line or restriction and carbon buildup. If carbon buildup exists,
at full governed compressor check for proper compressor cooling. Replace faulty
rpm. The discharge cavity. discharge line sections.
manufacturer
certifies that 3.D. Slipping drive 3.D.1. Check for faulty drive gears and couplings. Replace
minimum components. as necessary.
compressor 3.E. Excessive air 3.E.1. Test for excessive system leakage and repair as
performance meets system leakage. necessary. Use the following as a guide: Build the
Federal system pressure to governor cut-out and allow pressure
requirements. Do to stabilize for one minute. Using the dash gauge, note
not downsize the the system pressure and the pressure drop after two
original equipment minutes. The pressure drop should not exceed 2 psi in
compressor. each reservoir.
3.F. Sticking unloader 3.F.1. Check the unloading mechanism operation. Check for
pistons. proper compressor air governor operation.
If the governor is operating properly, replace the
unloader mechanism.
Inspect for bent, kinked or blocked tubing leading to or
from the governor.
3.G. Faulty compressor. 3.G.1. Replace or repair the compressor after determining
none of the preceding installation defects exists.

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Printed in Canada.
 Date March 2003 Page 4B-12

4. Compressor does 4.A. Faulty governor or 4.A.1. Test the governor for proper operation and inspect air
not unload. governor lines to and from the governor for kinks or restrictions.
installation. Replace or repair the governor or air lines.
4.B. Faulty or worn 4.B.1. Inspect for worn, dirty or corroded unloader pistons
unloader pistons or and their bores. Replace as necessary.
bores.
5. Compressor leaks 5.A. Damaged 5.A.1. Check the compressor mounting bolt torque. If the
oil. mounting gasket. mounting bolt torque is low, replace the compressor
mounting gasket before retorquing the mounting bolts.
5.B. Cracked 5.B.1. Inspect the compressor exterior for cracked or broken
crankcase or end components. Cracked or broken crankcases or
cover. mounting flanges can be caused by loose mounting
bolts. The end cover can be cracked by overtorquing
fitting or plugs installed in the end cover. Replace or
repair as necessary.
5.C. Loose end cover 5.C.1. Check capscrew torques and tighten as necessary.
cap screws.
5.D. Loose oil supply or 5.D.1. Check the torque of external oil line fittings and
return line fittings. tighten as necessary.
5.E. Porous 5.E.1. Replace the compressor if porosity is found.
compressor casing.
5.F. Mounting flange or 5.F.1. Replace as necessary.
end cover, O-ring or
gasket - missing,
cut or damaged.
6. Compressor 6.A. Leaking 6.A.1. Remove the compressor inlet air strainer or fitting.
constantly cycles compressor With the compressor unloaded, check for air leakage.
(compressor unloader pistons. Replace as necessary.
remains unloaded
for a very short 6.B. Faulty governor. 6.B.1. Test the governor for proper operation. Repair or
)
time). replace it as necessary.
6.C. Excessive system 6.C.1. Test for excessive system leakage as in #3E. Reduce
leakage. leakage wherever possible.
6.D. Excessive reservoir 6.D.1. Drain reservoirs.
contaminants.
7. Compressor head 7.A. Restricted 7.A.1. Clear the restriction or replace the line.
g
gasket failure. discharge line.
7.B. Loose head bolts. 7.B.1. Tighten evenly to a torque of 25-30 ft-lbs.
7.C. Faulty compressor 7.C.1. Check for rough or poorly machined head or block
or head gasket. surfaces. Replace the compressor if necessary.

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 4B-13

GOVERNOR
GENERAL DESCRIPTION OPERATION
The governor mounts directly to the air dryer support The governor’s cut-in and cut-out settings control the
and maintains air pressure within cut-in and cut-out compressor’s loading and unloading operations,
pressures. The governor monitors system pressure at responding to system pressure, which is monitored at
the supply reservoir. the accessory reservoir.
As system air pressure drops to the governor’s cut-in
COMPONENTS setting, reduced air pressure against the piston allows
The governor has a piston, adjusting screw and
the spring tension to move the piston down. The exhaust
pressure setting spring.
stem opens, while the inlet valve closes. With the
The governor has reservoir, unloader and exhaust
exhaust open, the air in the unloader control line and
ports (Figure 9). The reservoir port is connected to the
unloader mechanism escapes through the piston and
accessory reservoir. One unloader port is connected to
out the exhaust port.
the air dryer and another unloader port is connected to
the compressor. The exhaust is open. During loading, the dryer control line is exhausted,
allowing the turbo cutoff piston to open the dryer’s
supply port. (See Section 4C.)
As system air pressure increases, air enters the
governor at one of the reservoir ports. The piston moves
IDENTIFICATION up and overcomes the pressure-setting spring tension.
TAG As pressure continues to build to the cut-out setting, the
exhaust stem contacts the adjustable set screw and
EXHAUST seats the inlet/exhaust valve, closing the exhaust
PORT passage and opening the inlet valve.
System air pressure flows around the open inlet valve
through the piston passage and out to the air dryer
purge valve.

MOUNTING
HOLES
UNLOADER
PORTS

RESERVOIR PORTS

FIGURE 9

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Printed in Canada.
 Date March 2003 Page 4B-14

MAINTENANCE INSPECTION
Governor Inspection Interval
Every 50,000 miles (80,000 km), 6 months or 1,500
operation hours, perform Governor Operating and
WARNING Leakage Tests.
Governor Operating Test
1. Park the coach on a level surface, apply
1. Start the engine and build up system air pressure.
the park brake and block the wheels.
2. The gauge reading should be 130 psi at governor
2. Turn the engine off. If the engine must be
cut-out.
running, use EXTREME CAUTION to avoid
personal injury. 3. Apply and release the brakes to reduce air pressure
in the system.
3. Switch the main battery disconnect OFF.
4. The gauge reading should be 100 psi at governor
4. Vent all reservoirs.
cut-in.
5. Wear safety glasses.
6. Do not connect or disconnect pressurized NOTE: If results are questionable, verify the dash
lines. gauge’s accuracy with a test gauge.
7. Ensure that system pressure has been de-
pleted before removing components. Governor Leakage Test
8. Never exceed recommended pressures. 1. Apply soap solution around the governor’s cover
and to the exhaust port.
9. Do not install, remove, disassemble or as-
semble a component until you have read 2. In the cut-in position, check the exhaust port.
and understood the procedure. Slight bubbling is permitted; leakage in excess of a
1-inch bubble in 3 seconds is not acceptable.
10. Use proper tools and follow precautions
Excessive leakage indicates a faulty inlet/exhaust
pertaining to their use.
valve or lower piston O-ring.
11. Use vendor replacement parts. Replace-
3. In the cut-out position, check the exhaust port.
ment hardware must be equivalent to the
Slight bubbling is permitted; leakage in excess of a
original.
1-inch bubble in 3 seconds is not acceptable.
12. Components that have stripped threads Excessive leakage indicates faulty seating of the
or damaged parts must be replaced, not inlet/exhaust valve, or a faulty exhaust stem O-ring
repaired. DO NOT machine or weld parts or upper piston O-ring.
unless approved by the manufacturer.
13. Before returning the coach to service, GOVERNOR ADJUSTMENT
ensure that components and systems are The pressure settings are adjustable; the pressure
restored to operating condition. range (20 psi) is not. Do not overadjust. Each 1/4 turn of
the adjusting screw raises or lowers the pressure
settings approximately 4 psi.
1. Unscrew the cover.
NOTE: Maintenance intervals given are for typical 2. Loosen the adjusting screw locknut.
highway and street operations. More frequent
3. To raise the pressure settings, turn the adjusting
maintenance is required for operation in dusty or dirty
screw counterclockwise.
environments.
4. To lower the pressure settings, turn the adjusting
screw clockwise.
NOTE: When given more than one interval option, 5. Tighten the adjusting screw locknut.
use whichever comes first. 6. Replace the cover.

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 4B-15

REMOVAL AND DISASSEMBLY If disassembly is required, measure the locknut

location, then remove the locknut (3) and upper
Governor Removal spring seat (4) from the adjusting screw. Remove
1. Turn the battery disconnect OFF. Block the wheels the pressure setting spring (5), lower spring seat
and vent the air system. (6), spring guide (7) and the other lower spring seat
2. Tag and disconnect the reservoir and unloader (8) from the adjusting screw (9).
lines. 7. Gently tap the governor on a flat surface. Remove
3. Remove the mounting capscrews, then the the exhaust stem (11), exhaust stem spring (12)
governor and its gasket. and piston assembly.
Governor Disassembly 8. Remove and discard the upper and lower piston
O-rings (10 and 18).
NOTE: Refer to Figure 10. 9. With a hooked wire, remove the exhaust stem
O-ring (14). Discard.
NOTE: Have a maintenance kit available prior to 10. Remove and discard the valve spring (17) and
disassembly. Some parts must be discarded. valve (16).
1. Using cleaning solvent and a brush, clean dirt and 11. Remove and discard the filters (20) from the
grease from the governor exterior. unloader and reservoir ports.
2. Unscrew the rubber cover (1) until it disengages Governor Parts Cleaning and Inspection
from the adjusting screw (9). 1. Clean parts in cleaning solvent.
3. Remove the two pipe plugs from the body. 2. Inspect the body for cracks or other damage.
4. Remove the cover O-ring. 3. Ensure that passageways in the body, exhaust
5. Using retaining ring pliers, remove the spring stem and piston are unobstructed.
assembly retaining ring (2). 4. If the screw-spring assembly was disassembled,
6. Remove the adjusting screw and spring assembly check the adjusting screw for crossed or stripped
from the governor body. threads or distortion.
NOTE: Disassembly of the spring assembly is not 5. Check springs for cracks, distortion or corrosion.
normally required. (Reuse it without washing, which
would remove lubrication.) Proceed to step 7. NOTE: Replace parts that are worn or damaged.

Note: Cover O-Ring is not shown.

1. Cover
2. Spring Assembly Retaining Ring 3. Locknut
4. Upper Spring Seat
5. Pressure Setting Spring 9. Adjusting Screw
6. Lower Spring Seat 7. Spring Guide
8. Lower Spring Seat 12. Exhaust Stem Spring
10. Upper Piston O-Ring
20. Filters
13. Washer
14. Exhaust Stem O-Ring
11. Exhaust Stem
16. Inlet/Exhaust Valve
18. Lower Piston O-Ring
19. Governor Body

17. Valve Spring

15. Piston

FIGURE 10

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 4B-16

ASSEMBLY AND INSTALLATION spring seat (4) on the adjusting screw (9). Screw
the upper spring seat onto the adjusting screw until
Governor Assembly the distance from the top of the seat to the bottom of
1. Lubricate the lower body bores, all O-rings and the adjusting screw is approximately 1-7/8 inches.
O-ring grooves using the lubricant provided. Install the locknut (3).
2. If the adjusting screw and spring assembly has 11. Install the adjusting screw and spring assembly
been disassembled, lubricate the spring guide and into the governor body.
screw.
12. Install the retaining ring (2). Ensure that it seats
3. Install exhaust stem O-ring in piston. completely.
4. Drop the inlet/exhaust valve (16) into place at the 13. Install the cover (1).
bottom of the piston.
14. Install filters (20) in ports. The head of a pencil may
5. Install the inlet/exhaust valve spring (17) with the
be used as an installation tool.
small end against the valve. Press down until the
large end snaps into the recess in the piston. 15. Install pipe plugs in the governor body.
6. Install the upper and lower piston O-rings (10 and Governor Installation
18). 1. Clean the mounting pads on the compressor and
7. Install the exhaust stem spring (12) in the piston governor.
with the large coil end next to the piston. 2. Clean connecting line or lines.
8. Install the exhaust stem (11) through the spring. 3. Ensure that the unloading port is clear and clean.
9. Install the assembled piston into the governor body. 4. Install the gasket and governor using capscrews.
10. If the spring assembly was not disassembled, 5. Connect air lines.
proceed to step 11.
If the spring assembly was disassembled, install Governor System Check
the lower spring seat (8), spring guide (7), spring Perform Governor Leakage Test and Governor
seat (6), pressure setting spring (5) and upper Operating Test. Adjust if necessary. See page 4B-14.

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 4B-17

TORQUE CHART
COMPRESSOR ASSEMBLY TORQUES
Cylinder Head . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265 - 292 in-lbs
Unloader Cap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 - 71 in-lbs
Governor Adapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 - 142 in-lbs
Rear End Cover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195 - 213 in-lbs
Crankcase Cover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 - 71 in-lbs
Crankshaft Nut . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1858 - 2567 in-lbs
Inlet/Discharge Fittings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 - 225 in-lbs
Inlet Port Fittings
7/8”-12 UNF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221 - 248 in-lbs
3/4”-14 NPT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 3 Turns From Finger Tight
Discharge Port Fittings
7/8”-12 UNF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221 - 248 in-lbs
3/4”-14 NPT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 3 Turns From Finger Tight
Water Port Fittings
3/4”-16 UNF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221 - 248 in-lbs
3/8”-18 NPT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 3 Turns From Finger Tight
Unloader Port Fittings
1/8”-27 NPT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 3 Turns From Finger Tight
Safety Valve Port
3/4”-16 UNF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221 - 248 in-lbs
1/2”-14 NPT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 3 Turns From Finger Tight
Oil Port 7/16”-16 UNF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 - 204 in-lbs
Pipe Plugs & Bushings
1/16 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 - 50 in-lbs
1/8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 - 105 in-lbs
1/4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130 - 170 in-lbs
3/8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160 - 200 in-lbs
1/2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200 - 270 in-lbs

GOVERNOR ASSEMBLY TORQUES

Bolt, Nut or Screw
Governor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175---225 in-lbs

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 4B-18

SPECIFICATIONS
COMPRESSOR
Make . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bendix Westinghouse
Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Type BA-921
Average Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 528
Number of cylinders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Bore size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.622 in.
Stroke . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.125 in.
Displacement @ 1250 RPM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.8 CFM
Maximum Recommended RPM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3000 RPM
Coolant Flow @ Minimum/Maximum RPM . . . . . . . . . . . . . 11.8 CFM @ 1800 RPM to 18.0 CFM @ 3000 RPM
Approximate horsepower required: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Loaded 1800 RPM at 120 PSIG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5 HP
Unloaded 1800 RPM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 HP
Maximum Inlet Air Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250˚F
Maximum Discharge Air Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 400˚F
Minimum Oil Pressure Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 PSI
Minimum Governor Cutout Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 PSI

GOVERNOR
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bendix
Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Type D-2, Hi-Temp
Average Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 lb.
Cut-Out (Unload) Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130 psi
Cut-In (Load-Up) Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 psi

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 Date March 2003 Page 4C-1

SECTION 4C

AIR DRYER AND OIL SEPARATOR

CONTENTS OF THIS SECTION

SUBJECT PAGE
Air Dryer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4C-2
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4C-2
Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4C-2
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4C-2
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4C-3
Inspections and Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4C-3
Rebuilding the Air Dryer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4C-4
Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4C-4
Disassembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4C-5
Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4C-7
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4C-7
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4C-8
Oil Separator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4C-11
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4C-11
Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4C-11
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4C-11
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4C-11
Inspection and Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4C-11
Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4C-12
Maintenance Kits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4C-12
Filter Element Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4C-12
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4C-13
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4C-14
Air Dryer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4C-14
Oil Separator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4C-14

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Printed in Canada.
 Date March 2003 Page 4C-2

AIR DRYER
GENERAL DESCRIPTION
The air dryer is downstream of the compressor. The CHARGE CYCLE
air dryer removes water and contaminants from the air.
In combination with the oil separator, the air dryer
ensures that the air delivered to the supply reservoir is
clean and dry.
Desiccant Bed
COMPONENTS
The air dryer is a desiccant cartridge secured to a Purge Orifice Purge Volume
die-case aluminum end cover by a single, central bolt.
The end cover has a check valve assembly, safety valve,
heater and thermostat assembly, three threaded air
connections (control, supply and delivery) and a purge Supply Port Delivery
valve assembly. The purge valve assembly has a purge Check Valve
valve mechanism and a turbo cutoff feature.

OPERATION
The air dryer alternates between a charge cycle and a
purge cycle. During the charge cycle, contaminants are FIGURE 1
removed from the air and collected in the air dryer.
During the purge cycle, contaminants are expelled from Purge Cycle
the air dryer and the desiccant is dried. Air from the governor enters the air dryer’s control
port. When the purge valve opens and the check valve
Charge Cycle closes, the dryer decompresses causing air in the purge
Air from the compressor discharge line enters the end volume to flow back through the desiccant, end cover
cover through the supply port. The air changes direction and sump, expelling water and other contaminants.
of flow several times and cools, causing contaminants to The air dryer purge cycle is in two stages: The first
condense and drop to the sump. The air then flows up purge and decompression cycle takes 15 to 30
between the outer and inner shells of the cartridge, seconds for the entire purge volume to flow through the
cooling further and losing more contaminants. When it desiccant bed. This occurs when air compressor
reaches the top of the cartridge, the air reverses governer cut ---out pressure (130 psi) is reached. A burst
direction and enters the desiccant bed where it dries as of air is heard at the exhaust when this first cycle occurs.
water vapor adheres to the desiccant. The dry air flows
The second stage is a continuous low pressure air
through a passage in the center of the cartridge bolt and
flow through the purge valve which remains open until
either exits through the delivery check valve and port, or
the compressor resumes loading for the first purge cycle
flows through the purge orifice into the purge volume.
to repeat. Until the first purge and decompression cycle
(See Figure 1.)
repeats, the air copressor pumps air out of the purge
valve to continuously remove contaminants from the
system.
NOTE: This low pressure continuous purge air flow
prevents contaminant build-up and freeze-up at the
purge valve.
Continuous air flow will be heard at the purge valve
with this purge system. This is normal and does not
necessarily indicate an air leak at the air dryer.
If an air leak is suspected, review the “Air Dryer
Troubleshooting” at the end of this section.

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MAINTENANCE 4. Check the heater and thermostat assembly as

follows. (These tests are only required for cold
weather operation.)
INSPECTIONS AND TESTS
S Electric Power to the Dryer (Figure 2)
Air Dryer Inspection With the engine run switch ON, check for voltage
Every 900 operating hours, 25,000 miles (40,000 km) at the heater and thermostat using a voltmeter or
or 3 months, inspect the air dryer. test light. Unplug the electrical connector at the air
1. Check for moisture in the air system by opening dryer and place the test leads on each of the pins
drain cocks and drain valves. If water is present, the of the male connector. If there is no voltage, look
desiccant cartridge may require replacement, but for an open circuit, blown fuse or corrosion on the
first verify that one of the following conditions is not circuit’s harness. Check to see that a ground
at fault: exists.
S An outside air source that bypassed the air dryer
was used to charge the system.
S Air usage is exceptionally high due to accessory
air demands that prevent the compressor from
loading and unloading normally. Check for high
air system leakage.
S The vehicle has been operated in climates where
the daily temperature range exceeds 30_F. This
may cause minor condensation in the air system.

NOTE: Small amounts of oil in the system are normal

and are not a reason to replace the desiccant.

2. Check the mounting bolts. Torque to 270 to 385 lb-in

(30.5 to 43.4 N.m) if necessary.
3. Perform Air Dryer Operation & Leakage Tests.

Air Dryer Operation & Leakage Tests

1. Build system air pressure to cut-out and observe the
test air gauge installed in the supply reservoir.
Check lines and fittings leading to and from the air
dryer for leaks. A rapid loss of pressure could
indicate a failed delivery check valve.
If a failed delivery check valve is suspected, shut the
engine off, drain system pressure to below the FIGURE 2
cut-in and drain residual air from the compressor
discharge line. Remove the plug adjacent to the
delivery port and apply a soap solution to the
S Thermostat and Heater Operation
opening. Apply air pressure to the delivery port. If
leakage at the opening exceeds a 1” (25 mm) Turn off the ignition and cool the thermostat and
bubble in 1 second, repair the check valve. heater assembly to less than 40_F (4_C). With an
2. With the compressor loaded, apply a soap solution ohmmeter, check the resistance between the
to the purge exhaust. If leakage exceeds a 1” (25 electrical pins on the air dryer connector half. The
mm) bubble in 1 second, service the purge valve resistance should be between 1.5 and 3.0 ohms
housing assembly. for a 12-volt heater assembly and between 6.0
and 9.0 ohms for a 24-volt assembly.
3. Close all air system drain cocks. Build up system
pressure to cut-out and note that the dryer purges Warm the thermostat and heater assembly to
with an audible escape of air. Apply and release the 90_F (32_C) and check the resistance. The
brakes until system air pressure reduces to cut-in. resistance should exceed 1000 ohms.
Note that the system once again builds full pressure If the resistance values are outside of these limits,
and is followed by a dryer purge. replace the heater and thermostat assembly.

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 Date March 2003 Page 4C-4

S Delivery Check Valve Maintenance Kit --- contains the

WARNING parts to replace the delivery port check valve.
S Heater and Thermostat --- contains a replacement
1. Park the coach on a level surface, apply the heater and thermostat assembly and related
park brake and block the wheels. components.
2. Turn the engine off. If the engine must be AIR DRYER REMOVAL
running, use EXTREME CAUTION to avoid
personal injury. Refer to Figure 3.
Use the following procedure if the entire dryer must be
3. Switch the main battery disconnect OFF.
replaced. Normal service does not require removal.
4. Vent all reservoirs. 1. Park the coach on a level surface, apply the park
5. Wear safety glasses. brake and block the wheels.
6. Do not (dis)connect pressurized lines. 2. Drain all air reservoirs.
7. Ensure that system pressure has been
depleted before removing components.
8. Never exceed recommended pressures. WARNING
9. Do not install, remove, disassemble or
assemble a component until you have read The compressor discharge line may
and understood the procedure. contain residual pressure.
10. Use proper tools and follow precautions
pertaining to their use. 3. Identify and remove the three air lines from the end
cover. Note the position of the ports relative to the
11. Use Bendix replacement parts. coach.
Replacement hardware must be equivalent to
the original. 4. Unplug the electrical connector from the heater and
thermostat.
12. Components that have stripped threads or
damaged parts must be replaced, not 5. Remove the four bolts that secure the upper and
repaired. DO NOT machine or weld parts lower mounting brackets. Remove the air dryer
unless approved by the manufacturer. from the coach.
13. Before returning the coach to service, 6. Mark the relationship of the saddle bracket (5) to the
ensure that components and systems are end cover (6). Remove the mounting strap (4) and
restored to operating condition. saddle bracket (5).
7. Mark the relationship of the lower bracket (9) to the
REBUILDING THE AIR DRYER end cover (6). Remove the lower mounting bracket
Use only Bendix parts. The following kits are available (9) from the end cover.
and can be installed without removing the air dryer from
the vehicle.
S Purge Valve Housing Maintenance Kit --- contains the
CAUTION
parts to rebuild the purge valve housing.
Do not clamp die-cast aluminum. To hold
S Desiccant Cartridge Replacement Kit --- contains the the end cover, install a pipe nipple in the
parts to change the desiccant cartridge. supply port. Clamp the nipple in the vise.
S Mounting Bracket Kit --- contains the upper and lower
Do NOT disassemble the desiccant
brackets and mounting hardware. cartridge. The cartridge contains a 150 lb
S Cartridge Bolt Kit --- contains a replacement cartridge (68 kg) spring that cannot be caged.
bolt and related o-rings.

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AIR DRYER DISASSEMBLY 9. Remove the retaining ring (30) and heater and
Refer to Figure 3. thermostat assembly (31) from the end cover.
Remove the o-ring (32).
NOTE: The following disassembly and assembly 10. Using a wrench, remove the safety valve assembly
procedures are for reference during a major rebuild.
(33).
Replacement parts and maintenance kits generally
do not require full disassembly. Follow the Air Dryer Parts Cleaning and Inspection
instructions provided with Bendix parts and kits.
1. Using solvent, clean all metal parts except the
1. Loosen the cartridge bolt (10). Separate the desiccant cartridge. Dry thoroughly.
desiccant cartridge (11) from the end cover (6). 2. If a metal part is to be reused, inspect for corrosion,
Remove the cartridge bolt from the end cover. pitting and cracks. Superficial corrosion or pitting
2. Remove both o-rings (12 & 13) from the cartridge on the exterior of the body is acceptable.
bolt. 3. Inspect the end cover bores for deep scuffing or
3. Remove the retaining ring (14) and purge valve gouges.
cartridge assembly (15) from the end cover. 4. Ensure that purge valve housing and end cover
4. Remove the shoulder bolt (16) from the bottom of passages are free of obstructions.
the purge valve housing (19) using a socket wrench 5. Inspect the pipe threads in the end cover. Clean old
and a large-blade screwdriver inserted in the slot on thread sealant from pipe thread.
top of the purge valve piston (20). Remove the 6. Inspect the purge valve piston seat for excessive
exhaust diaphragm (17) and the purge valve (18)
wear or scuffing.
from the purge valve housing.
7. Inspect the purge valve housing bore for excessive
5. Remove the o-rings (23 & 24) from the purge valve
wear or scuffing.
housing.
8. Inspect air line fittings for corrosion. Clean old
6. Remove the purge valve piston (20) and the piston
thread sealant from the pipe threads.
return spring (22).
7. Remove the o-ring (21) from the purge valve piston. 9. Ensure that the purge orifice in the cartridge bolt is
free of obstructions.
8. Remove the retaining ring (25) that secures the
check valve assembly in the end cover. Remove 10. Discard o-rings and replace them with new o-rings
and separate the perforated plate (26), check valve from the appropriate kit.
spring (27), check valve (28) and o-ring (29). 11. Replace any part that fails inspection.

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Date March 2003 Page 4C-6

FIGURE 3

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 4C-7

AIR DRYER ASSEMBLY between the connector body and thermostat.

Refer to Figure 3. Gently push the heater and thermostat assembly
into the end cover, ensuring that the heating
1. Coat o-rings, o-ring grooves and bores with barium
element enters the small diameter bore in the larger
base lubricant.
heater and thermostat bore.
2. Install the o-ring (21) in its groove on the purge valve
11. Secure the heater and thermostat assembly with
piston (20). Place the spring (22) in the bore of the
the retaining ring (30). Ensure that the retaining ring
purge valve housing (19), then insert the purge
is fully seated in its groove.
valve piston into the spring.
12. Install both o-rings (12 & 13) on the cartridge bolt
3. Install and center the exhaust diaphragm (17) on
(10). Using a twisting motion, insert the assembled
the shoulder bolt (16). Install the purge valve (18) on
cartridge bolt in the end cover (6).
the shoulder bolt, with its metal support side
against the diaphragm. 13. Install the desiccant cartridge (11) on the end
cover (6), ensuring that the cartridge is flush and
4. Push the purge piston (20) into the purge valve
properly seated. If necessary, rotate the cartridge
housing (19), and insert a large-blade screwdriver
slightly until the anti-rotation lugs align.
in the piston’s slotted head. While pressing the
purge piston with the screwdriver, install the 14. Tighten the cartridge bolt (10) to secure the
shoulder bolt (16) with exhaust diaphragm (17) and desiccant cartridge to the end cover. Torque the
purge valve (18) into the piston. Torque the cartridge bolt to 50 lb-ft (68 N.m).
shoulder bolt to 60 to 80 lb-in (7 to 9 N.m).
5. Install the two o-rings (23 & 24) on the purge valve
housing (19). Install the purge valve housing in the
CAUTION
end cover (6). Ensure that the purge valve housing
is fully seated. Secure it with the retaining ring (14). Do not over-torque the cartridge bolt.
Ensure that the retaining ring is fully seated.
6. Using a wrench, install the safety valve assembly
(33) into the end cover (6). AIR DRYER INSTALLATION
7. Install the o-ring (29) on the check valve body (28), 1. Using the marks made during removal, install the
pushing the o-ring down over the three guide lands lower mounting bracket (9) on the end cover (6).
until it is in the o-ring groove. Install the check valve Secure with cap screws and washers (7 & 8).
spring (27) on the check valve body so that the Torque cap screws to 25 to 30 lb-ft (34 to 40 N.m).
small coils of the spring slip over the check valve 2. Using the marks made during removal, install the
body. saddle bracket (5) and mounting strap (4) on the
8. Install the assembled check valve body, o-ring and end cover. Torque the mounting strap cap screw to
spring (27, 28 & 29) in the end cover (6) so that the 60 to 100 lb-in (7 to 14 N.m).
o-ring rests on its seat and the spring is visible. 3. Connect the electrical harness to the heater and
9. Install the perforated plate (26) in the end cover and thermostat. Be sure the lock tab snaps into place.
secure the check valve assembly with the retaining 4. Connect the three air lines to their corresponding
ring (25). Ensure that the retaining ring is fully ports on the end cover.
seated in its groove. 5. Perform Air Dryer Operation & Leakage Tests.
10. Install the o-ring on the heater and thermostat 6. Install the dryer on the vehicle with the four bolts that
assembly (31). Position the sponge rubber cushion secure the upper and lower mounting brackets.

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Printed in Canada.
 Date March 2003 Page 4C-8

AIR DRYER TROUBLESHOOTING

Condition Cause Correction
1. Dryer purges A. Excessive system leakage. A. Test for leakage and repair. Allowable
constantly. leakage is 1 psi/minute in service
reservoir.
B. Excessive leakage in fittings, hoses or B. Using soap solution, test for leakage at
tubing connected to the compressor, fittings, drain cock, valve, governor and
air dryer, oil separator or supply safety valve in supply reservoir. Repair
reservoir. or replace as necessary.
C. Defective delivery check valve in the C. Test check valve. Build system
air dryer’s end cover. pressure to cut-out. Wait 2 minutes for
completion of purge cycle. Using soap
solution at exhaust of purge valve,
leakage must not exceed a 1” bubble
in 5 seconds. Replace as necessary.
D. Defective governor. D. Test governor cut-in and cut-out
pressures and inspect for leaks in both
positions.
E. Compressor unloader mechanisms E. Remove air strainer or fitting from
leaking excessively. compressor inlet cavity. With
compressor unloaded, check for
unloader piston leakage. Slight leakage
is permissible.
F. Governor cycling rapidly because of F. With gauge at the governor’s reservoir
air starvation at the reservoir port. port, pressure must not drop below
cut-in pressure at the onset of the
unload cycle. If pressure drops, check
for kinks or restrictions in reservoir port
line. Line must be the same diameter or
larger than the lines connected to the
governor’s unloader ports.
2. Water in reservoirs. A. Air system was charged from outside A. If system must have outside air, pass
air that did not pass through the air air through the dryer. Minimize the
dryer. practice of filling with outside air.
B. Air dryer not purging. B. See #6.
C. Purge time insufficient because of C. See #1.
system leakage.
D. Purge time less than minimum D. Ensure that cartridge assembly is
allowable (30 seconds). properly installed and seated. Replace
desiccant cartridge/end cover o-ring.
E. Air bypasses the desiccant cartridge E. Ensure that cartridge assembly is
assembly. properly installed and seated. Replace
desiccant cartridge/end cover o-ring.
F. Excessive contaminants in desiccant F. Replace desiccant cartridge.
( . . . cont’d) cartridge.

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 Date March 2003 Page 4C-9

2. Water in reservoirs. G. Excessive air usage. Air dryer is not G. Charge Cycle Time --- During normal
(cont’d) compatible with vehicle air system re- operation, the compressor should re-
quirements. cover from cut-in to cut-out in 90 sec-
onds or less. If recovery time consis-
tently exceeds this limit and if non-
brake accessories are on the system, it
may be necessary to bypass the ac-
cessory responsible for high air usage.
Purge Cycle Time --- During normal op-
eration, the compressor must remain
unloaded for a minimum of 30 sec-
onds. This is the minimum required for
the regeneration of desiccant material.
If the purge time is consistently less
than the minimum, an accessory by-
pass system must be installed.
Compressor Size --- The air dryer was
designed for units rated up to 30 CFM.
If using the air dryer with a compressor
that has a rated displacement exceed-
ing 30 CFM, contact a Bendix repre-
sentative.
3. Safety valve on air A. Desiccant cartridge plugged. A. Check compressor for excessive oil
dryer exhausting air. passing and for correct compressor
installation. Repair or replace as neces-
sary. Replace desiccant cartridge.
B. Defective delivery check valve in end B. Test to determine if air is passing
cover. through the check valve. Repair or
replace.
C. Defective fittings, hose or tubing C. Check to determine if air is reaching
between air dryer, oil separator and the supply reservoir. Inspect for kinked
supply reservoir. tubing or hose. Check for undrilled or
restricted hose or tubing fittings.
D. Safety valve setting lower than the D. Reduce system pressure or replace
maximum system pressure. safety valve.
4. Constant exhaust at A. Air dryer purge valve leaking A. With compressor loaded, apply soap
the air dryer purge excessively. solution on purge valve exhaust to test
valve or unable to for excessive leakage. Repair purge
build system pres- valve as necessary.
sure during charge
cycle. B. Defective governor. B. Check governor cut-in and cut-out
pressures and for leakage in both
positions. Repair/replace as necessary.
C. Purge control line connected to C. Purge control line must be connected
reservoir or exhaust port of governor. to unloader port of governor.
D. Purge valve frozen open --- faulty heater D. Test heater and thermostat as
and thermostat, wiring, blown fuse. described in Maintenance section.
E. Excessive system leakage. E. See #1A.
F. Purge valve stays open --- supply air F. Repair purge valve and housing.
leaks to control.

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5. Cannot build system A. Inlet and outlet connections reversed. A. Connect compressor discharge to air
air pressure. dryer supply port. Reconnect lines
properly.
B. Check valve located in the supply B. Test check valve for proper operation.
reservoir is defective. Repair or replace as necessary.
C. Kinked or blocked discharge line. C. Check to determine if air passes
through discharge line. Check for
kinks, bends, excessive carbon
deposits or ice blockage.
D. Excessive bends in discharge line D. Discharge line must slope from
(water collects and freezes). compressor to air dryer with as few
bends as possible.
E. See #4E and 4F. E. See #4E and 4F.
6. Air dryer does not A. Broken, kinked, frozen, plugged or A. Test for air flow through purge control
purge or exhaust air. disconnected purge control line. See line when compressor is unloaded.
#1 to #6. Check for undrilled fittings. (See #4C.)
B. Faulty air dryer purge valve. B. After determining air reaches purge
valve (6A above), repair purge valve.
C. See #4B and #5. C. See #4B and #5.
7. Desiccant material A. This condition is almost always A. See #1 to #6.
being expelled from accompanied by one or more of
air dryer purge valve Conditions #1 to #6.
exhaust (may look
like whitish liquid, B. Air dryer not securely mounted. B. Add bracket supports or change air
paste or small (Excessive vibration.) dryer mounting location if necessary.
beads). C. Malfunctioning or saturated desiccant C. Replace desiccant cartridge.
OR cartridge.
Unsatisfactory D. Compressor passing excessive oil. D. Check compressor installation; if
desiccant life. symptoms persist, replace compressor.
E. Faulty heater and thermostat, wiring, E. Test heater and thermostat as
fuse not allowing purge. (Cold described in Maintenance section.
weather operation only.)
8. Constant seepage of A. Defective check valve in end cover. A. See #1C.
air at air dryer purge
valve exhaust during B. Leaking turbo cutoff valve. B. Repair/replace purge valve assembly.
purge mode. C. Leaking purge valve control piston C. Repair/replace purge valve assembly.
o-ring.
9. Dryer purge piston A. Compressor fails to unload. A. Faulty governor installation.
cycles rapidly in
unloaded mode.

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 Date March 2003 Page 4C-11

OIL SEPARATOR
GENERAL DESCRIPTION
The oil separator is immediately downstream of the air
dryer and upstream of the supply reservoir. The oil
separator removes oil aerosols from the air. In
combination with the air dryer, the oil separator ensures
that the air delivered to the supply reservoir is clean and
dry.

COMPONENTS
The oil separator is a filter element mounted in a
die-cast aluminum housing. The sump housing has a
drain valve for maintenance.

OPERATION
Air enters through the supply port and travels down
through the center of the filter element. As the air passes FIGURE 5
through the filter, oil is removed and collected in the
sump. The air travels back up and out through the
delivery port. (Figure 4) MAINTENANCE
INSPECTIONS AND TESTS
Oil Separator Inspection and Routine Service
Every 300 operating hours, 8000 miles (12,500 km) or
1 month:
1. Park the coach on a level surface, apply the park
brake and block the wheels.
2. Switch the main battery disconnect OFF.
3. Drain all reservoirs.
4. Open the drain valve and collect contaminants for
disposal.
5. Inspect for physical damage, such as chafed or
broken air lines and broken or missing parts.
6. Ensure that mounting bolts are tight.
7. Perform the Oil Separator Operation & Leakage
Test.
FIGURE 4 Oil Separator Operation & Leakage Test
1. Build air system pressure to the governor cut-out.
If the filter plugs and causes a pressure difference of 2. Shut off the engine.
approximately 20 psi between the air entering and 3. Using a soap solution, check lines and fittings
exiting the filter element, the element will move down leading to and from the oil separator for leaks.
against the spring, and the air will bypass the filter 4. Repair leaks exceeding a 1” (25 mm) bubble in 5
element. (Figure 5) seconds.

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OIL SEPARATOR REMOVAL FILTER ELEMENT REPLACEMENT

Normal service and parts replacement does not Refer to Figure 6.
require removal of the oil separator from the coach. Every 3600 operating hours, 100,000 miles (160,000
1. Park the coach on a level surface, apply the park km) or 12 months, replace the filter element as follows:
brake and block the wheels. 1. Park the coach on a level surface, apply the park
2. Switch the main battery disconnect OFF. brake and block the wheels.
3. Drain all reservoirs. 2. Switch the main battery disconnect OFF.
4. Identify and disconnect the two air lines.
3. Drain all reservoirs.
5. Remove the bolts that secure the brackets to the
4. Open the filter drain valve and collect contaminants
coach. Remove the oil separator from the coach.
for disposal.
MAINTENANCE KITS 5. Using detergent and water, clean the exterior of the
Use Bendix parts and follow the instructions in the kit. oil separator.
The following kits are available and can be installed
6. Unscrew the sump housing. If necessary, use a
without removing the oil separator from the vehicle.
strap wrench.
S Retrofit Kit --- contains the oil separator, bracket and
7. Remove and discard the filter element (1) and o-ring
drain valve. (Other fittings are required.)
(2).
S Maintenance Kit --- contains large o-ring and filter
(including o-ring). 8. Inspect the oil separator for damaged or missing
S Rebuild Kit --- contains large o-ring, filter (with o-ring), parts.
spring and spring locator. 9. Clean build-up from the drain valve.
S Replacement drain cock. 10. Install the replacement o-ring (2) into the channel
in the head.
COVER (SHOWS AIR 11. Insert the replacement filter element (1) --- guide
FLOW DIRECTION)
lands up --- into the sump so that its base rests on
DELIVERY
the spring (3).
SUPPLY PORT PORT 12. Coat the sump housing’s threads with lithium or
barium grease and screw the housing into the head
O-RING (2)
until it is hand tight. Take care not to damage the
large o-ring when installing the sump housing.
13. Ensure that mounting bolts are tight.
FILTER
14. Perform the Oil Separator Operation & Leakage
INTEGRATED
Test.
O-RING

FILTER ELEMENT (1) SPRING (3)

SPRING LOCATOR
DRAIN PORT

FIGURE 6

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OIL SEPARATOR TROUBLESHOOTING

Condition Cause Correction
1. Sump requires A. Oil separator installed in incorrect A. Oil separator must be downstream of
draining more than location in the system. the air dryer and upstream of the
once a month. supply reservoir.
B. Alcohol injector in system. B. The oil separator must not be used
with an alcohol evaporator or injector.
C. Air dryer malfunction. C. Check/service the air dryer.
D Compressor malfunction.
D. malfunction D Check/service the compressor.
D. compressor
2. Bypass feature not A. Supply and delivery air connections A. Reverse hose connections.
working. reversed.
3. Oil in system. A. Supply and delivery air connections A. Reverse hose connections.
reversed.
B. Sump not drained regularly. B. Drain sump every 300 operating hours,
8000 miles or one month.
C. Filter element maintenance interval C. Replace filter element every 3600
exceeded. operating hours, 100,000 miles or one
year.
D. Air dryer malfunction. D. Check/service air dryer.
E. Compressor malfunction. E. Check/service compressor.

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SPECIFICATIONS
AIR DRYER
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bendix
Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . AD-IP

OIL SEPARATOR
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bendix
Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PuraGuard

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SECTION 4D

AIR CONTROL COMPONENTS

CONTENTS OF THIS SECTION
SUBJECT PAGE
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4D-2
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4D-2
Park Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4D-2
Brake Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4D-3
Brake Pedal Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4D-5
Quick Release Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4D-5
Spring Brake Relay Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4D-6
Service Brake Relay Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4D-8
ABS Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4D-10
Pressure Protection Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4D-11
Reservoirs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4D-11
Double Check Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4D-12
Pressure Regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4D-12
Low Pressure Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4D-13
Pressure Transducers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4D-13
Air Horn . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4D-14
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4D-15

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GENERAL DESCRIPTION 5. Remove the mounting nut (2) and pull the valve out.
Disassembly
Various air control and regulating components are
1. Remove the capscrews (3), cover and sealing ring
used on the brake, suspension and accessory air
from the base of the valve.
systems. These components require periodic
maintenance. For an overview of the air system 2. Remove the nut (4) and washer using a rod in the
components, see Section 4A. plunger pin hole to keep the plunger from turning.
3. Remove the valve (5), plunger (6) and spring (7).
MAINTENANCE 4. Remove the O-ring (8).

PARK VALVE Cleaning and Inspection

The PP-1 parking brake control valve (Figure 1) Wash parts in a cleaning solvent and dry them
should be disassembled, cleaned and lubricated every thoroughly. Inspect all parts for wear or deterioration.
6 months, 50,000 miles (80,000 km) or 1,800 hours. Use Inspect the plunger and piston bores for nicks and burrs.
lubrication specification S-26 (Silicon Grease - DOW Check the body for damage. Replace any damaged
CORNING 55 O-Ring Lube) as shown in Section 10 of parts.
this manual. Inspect all parts and replace parts that are Assembly
worn or damaged.
1. Lubricate the O-rings and bore surfaces
(Specification S-26).
2. Assemble the valve in reverse order of
Disassembly.
3. Perform the Operation and Leakage Test on the
1 valve before installation.

6 Operating and Leakage Test

2 1. Connect an air source with gauge to the supply
port.
8 2. Connect an air gauge to the delivery port.
7
3. At 120 psi supply pressure, in the exhaust (button
out) position, leakage at the plunger stem and
exhaust port must not exceed a 1” bubble in five
5 seconds.
4. At 120 psi supply pressure, in the supply (button in)
4 position, leakage at the plunger stem and exhaust
3 port must not exceed a 1” bubble in five seconds.
5. With the valve in the supply (button in) position,
starting at 120 psi, gradually reduce the supply
pressure. (The delivery pressure will also drop.) At
FIGURE 1 20 - 60 psi, depending on the spring used, the
button should automatically pop put, exhausting
Removal the delivery port.
1. Switch battery disconnect to OFF and block the NOTE: If the valve does not function as described or
coach. if leakage is excessive, replace the valve.
2. Drain all air from reservoirs.
3. Remove the roll pin (1) and knob from the valve. Installation
4. Bleed all air from the supply and delivery lines and 1. Install the valve in the reverse order of Removal and
remove the air lines. test for proper operation.

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BRAKE VALVE E-15 Brake Valve

The brake valve (Figure 2) should be inspected,
cleaned and lubricated at regular intervals. Replace
parts that are worn or damaged. E-15-R brake valves are
used with transmission retarder installations, and may
have additional pressure switches.

WARNING
Poor braking characteristics or a low
pressure warning may indicate a
malfunction in one of the brake circuits.
Although the vehicle air system may
continue to function, do not operate the
vehicle until making the necessary repairs.
Always check the vehicle brakes after brake
system maintenance and before returning
the vehicle to service.

Every 25,000 miles (40,000 km), 750 operating hours,

make a Service Check and Leakage Check. Clean any
dirt from exterior of brake valve, and inspect the plunger
boot for cracks or other damage. Lubricate the plunger
using lubrication specification S-25 (Silicon Fluid - DOW
CORNING 200) as shown in Section 10 of this manual.

Service Check
Check the primary and secondary service circuits
using test gauges known to be accurate. Test fittings are
provided on the primary and secondary delivery circuits
of the brake valve. Depress the pedal to several
positions between fully released and fully applied and
check the delivered pressure on the test gauges. The
pressures should vary proportionally to the movement of 11. VALVE SEAT
12. O-RING
the brake pedal.
13. VALVE ASSEMBLY
Charge the air system to governor cut-out and make a 14. RETURN SPRING

full service brake application. The primary delivery 15. O-RING

should be within 5 psi (34 kPa) of the primary reservoir 1. PISTON RETAINING RING 16. CAPSCREW
2. PISTON 17. O-RING
pressure. Secondary brake delivery pressure should be 3. O-RING 18. SECONDARY PISTON
about 2 psi (14 kPa) lower than the primary delivery 4. WEAR RING 19. O-RING
pressure under normal conditions. After the brake pedal 5. O-RING 20. O-RING
is released, the reading on the test gauge should 6. RETAINING SPRING 21. PLUNGER
promptly fall off to zero. 7. SPRING RETAINER 22. RETURN SPRING
8. GRADUATING SPRING 23. SPRING RETAINER
With the air system recharged to governor cut-out, 9. RUBBER SPRING 24. EXHAUST DIAPHRAGM RETAINER
drain the primary reservoir and make a full service brake 10. RETAINING SPRING 25. EXHAUST DIAPHRAGM
application. The secondary output should be within 5 psi
(34 kPa) of the secondary reservoir pressure. If the
output is too low, the brake valve linkage may need FIGURE 2
adjustment.

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Leakage Check 8. Using finger force, push the piston (2) into the body
1. Coat the exhaust port and body of the brake valve until the retaining ring (1) is fully visible. Remove the
with a soapy solution. retaining ring (1), taking care not to damage the
2. Hold a brake application to 20 psi (140 kPa). bore in the body.
3. Leakage must not exceed a 1” (35 mm) bubble in 9. Gently tap the body on a soft surface to remove the
three seconds. piston (2). Remove and discard the O-rings (3 and
5) and wear rings (4).
NOTE: If the brake valve has excessive leakage, 10. Place the piston on a flat surface. Using finger
repair it and perform another leakage check. force, depress and hold the spring retainer (7), then
remove and discard the retaining ring (6).
Every 100,000 miles (160,000 km) or 12 months the 11. Gently release the spring retainer (7). Remove the
brake valve should be disassembled, cleaned and spring retainer (7) and graduating spring (8).
inspected. Replace any worn or damaged parts.
12. Remove and discard the beveled retaining ring
Removal (10) from the piston (2) while manually holding the
valve seat (11) in place.
1. Switch the battery disconnect OFF and block the
coach. 13. Slowly release the valve seat (11). Remove the
valve seat (11), then remove and discard the O-ring
2. Vent the entire air system.
(12).
3. Disconnect all supply and delivery lines at the brake
valve. 14. Remove and discard the valve assembly (13) and
O-ring (15 from the piston (2). Remove the valve
NOTE: Label all air lines. assembly return spring (14).

4. Remove the mounting bolts from the mounting

plate.
5. Remove the assembly from the floor.
WARNING
Disassembly The combined force of the internal springs
is approximately 50 pounds (23 kg). Take
NOTE: If a vise is used, position the valve so that the care when removing the lock nut as the
jaws bear on the delivery and supply ports on springs will be released. The primary piston
opposing sides of the valve’s upper body. and relay piston must be manually or
mechanically contained while the lock nut
and stem are being removed.
1. Remove all fittings and brake light switch.
2. Mark the relationship of the upper to the lower body
(scribed line). Remove the capscrews (16) and
separate the two body halves. Remove and discard Assembly
the O-ring (17). 1. Clean all metal parts in solvent. Dry and inspect all
3. Pull the secondary piston (18) from the upper body parts for wear or deterioration. Check the springs
and discard the O-rings (19 and 20) from it. for cracks, corrosion and permanent set. Replace
4. Remove and discard the beveled retaining ring (10) all rubber parts found to be unserviceable.
from the lower body while manually holding the 2. Lubricate all O-rings, O-ring grooves, piston bores
valve seat (11) in place. and metal contact surfaces. Use lubrication
5. Slowly release the valve seat (11). Remove the valve specification S-26 (Silicon Grease - Dow Corning 55
seat (11) and remove and discard the O-ring (12). O-ring lube) as shown in Section 10.
6. Remove and discard the valve assembly (13) and 3. Assemble the valve in the reverse order of
O-ring (15). Remove the valve assembly return Disassembly.
spring (14). 4. Perform a Leakage Check.
7. Remove and discard the exhaust diaphragm
retainer (24) and diaphragm (25). Installation
1. Mount the brake valve in the reverse order of
NOTE: Brake valves may have a threaded exhaust Removal and torque the valve mounting fasteners
port in lieu of items 24 and 25. to 40 lb-ft (54 Nm).

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BRAKE PEDAL ASSEMBLY QUICK RELEASE VALVE

Every 12 months, 100,000 miles (160,000 kms) or
Inspection 3600 operating hours:
Every 25,000 miles (40,000 km) or 900 operating 1. Remove and disassemble the valve. (See Removal
hours:
and Disassembly.)
1. Clean dirt, gravel and other contaminants away 2. Wash metal parts in mineral spirits.
from the treadle heel, plunger, plunger boot and
3. Inspect all parts for wear or damage. Repair or
mounting plate.
replace damaged parts.
2. Using S-6 (light engine oil) as shown in Section 10,
4. Replace ALL rubber parts.
lubricate the treadle roller, roller pin and hinge pin.
5. Assemble and install the valve. (See Assembly and
3. Inspect the plunger boot for holes, cracks or
Installation.)
deterioration and replace it if necessary. Check the
mounting plate and treadle for wear and corrosion. 6. Perform the Operating and Leakage Test.
Replace or repair as required. Operating and Leakage Test
4. Apply two to four drops of oil between the plunger 1. Coat the valve body and all parts with a soap
and mounting plate. Do not over-lubricate these solution.
parts. 2. While holding a full brake application, check for
5. Check for excessive air leakage. leakage:
a. The valve body and cover must have no leakage.
Operation and Leakage Tests
b. The exhaust port leakage must not exceed a 1”
Every 100,000 miles (160,000 km) or 3,600 operating
(25 mm) bubble in three seconds.
hours, perform the following test:
3. If the valve fails the leakage test, repair or replace it.
1. Operation: Check the delivery pressure of the
primary and secondary circuits. Removal
1. Switch the battery disconnect OFF and block the
coach.
SUPPLY
2. Remove the supply and delivery air lines.
3. Remove the mounting bolts and remove the valve.
Disassembly
1. Remove the screws and separate the two body
DELIVERY DELIVERY halves.
2. Remove the O-ring and diaphragm.
Assembly
1. Center the diaphragm in the upper body and
SEALING RING EXHAUST
DIAPHRAGM position the O-ring on the lower body.
2. Join the halves, install the screws and torque to 60
QUICK-RELEASE VALVE lb-in (6.8 N·m).
Installation
FIGURE 3 1. Install the valve in the reverse order of Removal.

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SPRING BRAKE RELAY VALVE 4. With the spring brakes released, coat the exhaust
Every 100,000 miles (160,000 km), 3,000 operating port and balance port with soap solution. Leakage
hours: must not exceed a 1” (25 mm) bubble in three
seconds.
1. Disassemble.
5. With the spring brakes released, apply soap
2. Clean and inspect all parts.
solution where the cover joins the body to check for
3. Install new rubber parts. seal ring leakage. No leakage is permitted.
4. Replace any worn or damaged parts. 6. If the valve does not function properly or leakage is
5. Assemble. excessive, it must be repaired or replaced.
6. Perform Operational and Leakage Test. Removal
Every 25,000 miles (40,000 km) or 900 operating 1. Switch the battery disconnect OFF, block the coach
hours perform the Operational and Leakage Test: and vent the entire air system.
2. Label and remove all air lines from the relay valve.
3. Unfasten and remove the valve.
EXHAUST BALANCE/QUICK
COVER EXHAUST PORT Disassembly
(ANTI---COMPOUND)
EXHAUST 1. Match-mark the location of the mounting bracket to
SEAT the cover and the cover to the body.
2. Remove the capscrews and lockwashers from the
cover.
3. Carefully remove the cover, sealing ring and
mounting bracket. (The piston is under spring
force.)
4. Remove the piston and O-ring.
DIAPHRAGM
5. While depressing the exhaust cover, remove the
retaining ring and slowly remove the exhaust cover.
6. Remove the O-rings and inlet/exhaust valve return
RELAY spring.
PISTON
7. Remove the inlet/exhaust valve.
8. Remove the valve retainer from the inlet/exhaust
RETAINING EXHAUST
RING PORT INLET/EXHAUST valve.
VALVE ASSEMBLY 9. Remove the screw and exhaust cover from the body
cover.
R-14 SPRING BRAKE RELAY VALVE 10. Remove the service port capnut and O-ring.
11. Remove the diaphragm from the cover.
FIGURE 4
Cleaning and Inspection
1. Wash all parts in mineral spirits and dry all rubber
Operational and Leakage Test parts.
1. Block the coach, charge the air system and adjust
the brakes. NOTE: When rebuilding, replace all springs and
rubber parts.
2. Check that the spring brakes apply and release
promptly at each wheel. 2. Inspect all parts for wear and deterioration. Inspect
3. wit the spring brake applied (park), coat the exhaust springs for cracks, distortion or corrosion.
port and the area around the retaining ring with 3. Inspect the inlet seat and exhaust seat for nicks and
soap solution. Leakage must not exceed a 1” (25 burrs and replace them as necessary. Replace all
mm) bubble in three seconds. worn and deteriorated parts.

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4. Install the sealing ring on the cover.

BRACKET 5. Install the piston in the body, taking care not to
damage the O-ring.
6. Align the match-marks and install the cover on the
CONTROL
valve body and the mounting bracket on the cover.
7. Tighten the capscrews and lockwashers to 80-120
lb-in (9-14 N.m) torque.
8. Install the valve retainer on the inlet/exhaust valve
and install in the body.
9. Install the inlet/exhaust valve return spring in the
body.
10. Install the exhaust cover assembly in the body,
taking care not to damage the O-ring.
11. While depressing the exhaust cover, install the
retaining ring. Ensure that the retainer is completely
seated in its groove.
SUPPLY DELVERY 12. Install the service port O-ring on the cap nut.
13. Install the service port diaphragm in the cover.
R-14 SPRING BRAKE RELAY VALVE Ensure that it is positioned between the guide ribs
in the cover.
14. Install the service port cap nut and torque it to 150
FIGURE 5
lb-in (17 Nm).

Assembly Installation
1. Lubricate all O-rings, O-ring bores and sliding 1. Clean the air lines and fittings.
surfaces with lubrication specification S-25 (silicon 2. Install the valve and torque the mounting bolts to
fluid - Dow Corning 200) as shown in Section 10. 20-25 ft-lbs (27-34 N·m).
2. Install the large O-ring on the piston. 3. Connect the air lines to the valve.
3. Install the inner and outer O-rings in the exhaust 4. Perform an Operational and Leakage Test before
cover assembly. returning the valve to service.

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SERVICE BRAKE RELAY VALVE Removal

1. Switch the battery disconnect OFF. Block the coach
NOTE: The operation and maintenance of the
and vent the entire air system.
R-12DC is very similar to the R-14. Differences include
their application (service vs spring brake), leakage 2. Label and remove all air lines from the relay valve.
test and assembly/disassembly procedures. 3. Unfasten and remove the valve.
Disassembly
NOTE: The components and appearance of the 1. Match-mark the location of the mounting bracket to
spring brake R-14 and the service brake R-12DC are the cover, the cover to the body, and the secondary
similar. The R-14 has one control port and one control port cover to the body.
balancing port. The R-12DC has two control ports and 2. Carefully remove the capscrews and lockwashers
no balancing port. (Figure 4) from the cover. (The piston may be under spring
force.)
Every 100,000 miles (160,000 km), 3,000 operating
hours: 3. Remove the cover, sealing ring and mounting
bracket. Discard the sealing ring.
1. Disassemble.
4. Remove the screws from the secondary control port
2. Clean and inspect all parts.
cover.
3. Install new rubber parts.
5. Remove the secondary control port cover.
4. Replace any worn or damaged parts.
6. Remove and discard the spring, guide, diaphragm
5. Assembly. and O-ring.
6. Perform Operational and Leakage Test.
7. Remove the piston and O-ring from the body.
Every 25,000 miles (40,000 km) or 900 operating Discard the O-ring.
hours perform an Operational and Leakage Test.
8. While depressing the exhaust cover, remove and
Operational and Leakage Test discard the retaining ring.
1. Block the coach, charge the air system and adjust 9. Slowly remove the exhaust cover assembly.
the brakes. Discard the exhaust cover.
2. Check that the service brakes apply and release 10. Remove and discard O-rings and the inlet/exhaust
promptly at each wheel. valve return spring.
3. With the service brakes released, coat the exhaust 11. Remove and discard the inlet/exhaust valve.
port and the area around the retaining ring with 12. Remove the valve retainer from the inlet/exhaust
soap solution. Leakage must not exceed a 1” (25 valve.
mm) bubble in three seconds. 13. Remove the diaphragm from the cover.
4. With the service brakes fully applied, coat the
exhaust port and area around the retaining ring with Cleaning and Inspection
soap solution. Leakage must not exceed a 1” (25 1. Wash all parts in mineral spirits and dry all rubber
mm) bubble in three seconds. parts.
5. With the service brakes fully applied, coat the valve NOTE: When rebuilding, replace all springs and
with soap solution where the cover joins the body to rubber parts.
check to seal ring leakage. No leakage is permitted.
6. If the valve does not function properly or leakage is 2. Inspect all parts for wear or deterioration. Inspect
excessive, it must be repaired or replaced. springs for cracks, distortion or deterioration.

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Assembly 11. While depressing the exhaust cover, install the

1. Lubricate all O-rings, O-ring bores and sliding retaining ring. Make certain the retainer is
surfaces with lubrication specification S-25 (silicon completely seated in its groove.
fluid - Dow Corning 200) as shown in Section 10. 12. Install the O-ring on the secondary control port
2. Install the O-ring on the piston. cover.
3. Install the sealing ring on the cover. 13. Align and install the spring, guide and diaphragm
4. Install the piston in the body, taking care not to in the cover.
damage the O-ring. 14. Install cover screws and torque to 80-100 lb-in
5. Align the match-marks and install the cover on the (9-11 Nm).
valve body and the mounting bracket on the cover. 15. Install the exhaust port cover and screw. Torque it
6. Torque the capscrews and lockwashers to 80-120 to 15-25 lb-in (1.7-2.8 Nm).
lb-in (9-14 Nm). Installation
7. Install the O-rings on the exhaust cover assembly. 1. Clean the air lines and fittings.
8. Install the valve retainer on the inlet/exhaust valve 2. Install the valve and torque the mounting bolts to
and install in the body. 20-25 lb-ft (27-34 Nm).
9. Install the inlet/exhaust valve return spring in the 3. Connect air lines to the valve and plug unused
body. ports.
10. Install the exhaust cover assembly in the body, 4. Perform Operational and Leakage Test before
taking care not to damage the O-ring. returning the coach to service.

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 4D-10

ABS VALVE NOTE: If leakage is evident, tighten the cover

capscrews and re-test the valve.
NOTE: The modulator valve is not serviceable.
Damaged or non-functioning valves must be 5. If leakage is excessive, replace the modulator valve.
replaced.
Operational Test
Every 25,000 miles (40,000 km) or 750 operating NOTE: Two technicians are required for this test.
hours: (Figure 6).
1. Clean the exterior and inspect it for excessive 1. Block the coach and charge the air system.
corrosion and physical damage.
2. Release the parking brakes.
2. Inspect air lines and electrical harnesses for 3. Turn the ignition off.
damage.
4. Make and hold a full brake application.
3. Perform the Operational Test and Leakage Test.
5. Turn the ignition on. A technician near the valve
should hear one or two short air bursts from the
exhaust port.
6. Repeat the test for all valves on the coach. If there is
not a short burst of air, or the exhaust is prolonged
(not sharp and well-defined), perform the Electrical
Test.

Electrical Test
1. Block the coach and switch the battery disconnect
OFF.
2. The resistance of the valve solenoid coil can be
measured at the valve or at the ECU wire harness.
Disconnect the electrical harness at the valve or at
Wabco ABS the ECU.
Modulator Valve
3. The resistance of the solenoid coil must be 4.0 to 8.0
FIGURE 6 ohms:
a. If the resistance is extremely high when tested
through the electrical harness, check the
harness for damage and retest the resistance at
Leakage Test the valve.
1. Block the coach, charge the air brake system and b. If the resistance is slightly higher than 8.0 ohms,
adjust the brakes. clean the terminals/connector and retest.
2. Check that the brakes apply and release properly. c. If the resistance is less than 4.0 ohms, clean the
3. Recharge the air system and turn the engine off. terminals/connector and retest.
4. Make and hold a full service brake application. 4. Replace any electrical harness or valve that fails the
a. Coat the exhaust port with soap solution. test.
Leakage must not exceed a 1” (25 mm) bubble
in three seconds. Removal
1. Switch the battery disconnect OFF. Block the coach
b. Coat the solenoid to valve joint with soap and vent the entire air system.
solution. Leakage must not exceed a 1” (25 mm)
bubble in three seconds. 2. Clean dirt from the valve and fittings.
3. Label and remove all air lines. Disconnect the
NOTE: If leakage is evident, tighten the solenoid harness from the unit.
capscrews and re-test the valve. 4. Unfasten and remove the valve.

c. Coat the exhaust and supply diaphragm covers Installation

with soap solution. Leakage must not exceed a 1. Install the valve in the reverse order of Removal.
1” (25 mm) bubble in three seconds. 2. Perform the Operational Test and Leakage Test.

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 4D-11

PRESSURE PROTECTION VALVE 3. Unfasten and remove the valve.

NOTE: Two PR-4 pressure protection valves are Installation

used. They have different closing pressures: (1) The 1. Install the valve in the reverse order of Removal.
auxiliary/suspension PR-4 is set at 70 psi. (2) The fan
clutch control PR-4 is set at 90 psi.

Every 25,000 miles (40,000 km), or 900 operating

hours, perform the Operational Test and Leakage Test.

Leakage Test
1. Block the coach and fully charge the air system.
2. Turn the engine off.
3. Switch the battery disconnect OFF.
4. Coat the valve cap with soap solution. Leakage
must not exceed a 1” (25 mm) bubble in three
seconds.
5. Drain the air pressure from the delivery side of the
valve. Disconnect the delivery port line and coat the
port with soap solution. Leakage must not exceed a
1” (25 mm) bubble in five seconds.
6. If leakage is excessive, repair or replace the valve. PR-4 Pressure Protection Valve
Operational Test FIGURE 7
1. Install pressure gauges on the supply and delivery
sides of the valve.
2. Install a drain valve on the delivery side.
3. Follow steps 1 through 3 of Leakage Test.
RESERVOIRS
4. While watches the gauges on both sides, slowly
exhaust air from the delivery side of the valve. Air compressors pass some oil and water vapor into
5. When the supply side pressure no longer drops, the the reservoir. When the vapor cools it condenses to an oil
closing pressure has been reached. and water emulsion. Reservoirs have a pull-type drain
cock at the bottom. They should be drained frequently.
NOTE: Both sides should show pressure loss until the At regular intervals, check the reservoirs for mounting
the closing pressure of the valve is reached. Closing integrity, corrosion or damaged lines and fittings.
pressures should be noted on valve. Opening
pressure is approximately 10 psi greater than closing Removal
pressure. 1. Switch the battery disconnect OFF. Block the coach
and vent the entire air system.
2. Label and remove all air lines.
Removal
3. Remove the fasteners and remove the reservoir.
1. Switch the battery disconnect OFF. Block the coach
and vent the entire air system. Installation
2. Label and remove all air lines. 1. Install the reservoir in the reverse order of Removal.

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 4D-12

DOUBLE CHECK VALVE PRESSURE REGULATOR

Every 25,000 miles (40,000 km), or 750 operating Every 50,000 miles (80,000 km) or 1,500 operating
hours, perform the Operational and Leakage Test. It hours, check the regulator valves and reset them to their
may be necessary to remove the check valve for the test. proper set pressures:
1. Lavatory door . . . . . . . . . . . . . . 21 psi (145 kPa)
2. Transmodulator . . . . . . . . . . . . . 70 psi (482 kPa)
Operational and Leakage Test 3. Lavatory air flush . . . . . . . . . . . . 15 psi (103 kPa)
1. Disconnect one supply line from the valve.
Every 100,000 miles (160,000 km) or 3,000 operating
2. Apply air pressure to the other supply port. hours:
3. Coat the open inlet port with soap solution. Leakage 1. Remove the regulator valves.
must not exceed 1” (25 mm) bubble in five seconds. 2. Disassemble.
4. Repeat steps 1 through 3. 3. Clean and inspect.
4. Replace the diaphragm and any damaged parts.
Every 100,000 miles (160,000 km), or 3600 operating
hours: Removal
1. Switch the battery disconnect OFF. Block the coach
1. Disassemble.
and vent the entire air system.
2. Clean and inspect all parts. 2. Disconnect the air lines.
3. Replace all rubber parts. 3. Unfasten and remove the valve.
4. Replace any parts showing wear or deterioration. Disassembly
5. Assemble 1. Unfasten the screws and separate the body halves.
2. Separate the valve halves and remove the
diaphragm(s), springs and spring retainers.
Removal
3. Remove the bottom cover poppet and spring.
1. Switch the battery disconnect OFF. Block the coach
and vent the entire air system. Cleaning and Inspection
1. Wash all metal parts in cleaning solvent.
2. Label and remove all air lines.
2. Inspect the inside of the valve for wear or damage.
3. Unfasten and remove the check valve. Replace a damaged valve.
Testing
Disassembly 1. Vent the air system.
1. Unfasten the capscrews and remove the check 2. Install an air gauge on the outlet side of the pressure
valve cap. regulating valve into the tee fitting.
2. Remove the shuttle and shuttle guides from the 3. Charge the air system.
valve body. 4. Loosen the locknut and turn the adjusting screw
counterclockwise to reduce the pressure
approximately 10 psi (70 kPa) below the desired
Assembly pressure.
1. Install the shuttle guides and the shuttle into the 5. Slowly turn the adjusting screw clockwise to
valve body. increase the pressure until the desired pressure is
2. Install the cap and torque the fasteners to 60 lb-in reached.
(6.8 N·m). 6. Tighten the locknut.
7. Apply a soap solution to the valve and check for
leakage.
Installation
1. Install the check valve in the reverse order of Assembly
Removal then test it. 1. Assemble the valve in the reverse order of
Disassembly.
When installing the valve, make certain that it is 2. Perform the pressure test.
installed correctly with respect to the desired air flow.
The direction of air flow is clearly marked on the valve Installation
body. 1. Install regulator in the reverse order of Removal.

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 4D-13

LOW PRESSURE SWITCH 2. Apply the park brakes.

Pressure switches are used for: 3. Ensure that the hazard lights activate.
a. Supply reservoir low air warning telltale and buzzer. 4. If hazard lights do not go on:
b. Primary service brake light switch. a. Check for a damaged electrical harness and
c. Secondary service brake light switch. blown fuse.
d. Park brake hazard light switch. b. Repeat the test.
Every 100,000 miles (160,000 km) or 3,000 operating
hours:
Removal
1. Switch the battery disconnect OFF. Block the coach
1. Inspect and test the low air pressure switches.
and vent the entire air system.
Test (Supply Reservoir Low Air) 2. Remove the electrical connector from the switch.
1. Apply the park brakes. 3. Remove the switch.
2. Charge the air system and turn the engine off.
3. Turn the ignition on (do not start the engine). Installation
1. Install the switch in the reverse order of Removal.
4. Apply and release the service brakes several times
while watching the air gauges.
5. The Low Air telltale and buzzer must activate at 75 ±
5 psi (520 ± 35 kPa).
Test (Primary Service Brake Light) PRESSURE TRANSDUCERS
1. Charge the coach air system and apply the park
Every 100,000 miles (160,000 kms) or 3,000
brake.
operating hours, inspect and test the pressure
2. Turn off the engine. transducers. The transducers control the dash air
3. Vent the secondary service reservoir only. gauges and gauge telltales.
4. Make a service brake application and ensure that
the brake lights illuminate. Test
1. Apply the park brakes.
5. If the brake lights do not light:
a. Check for a damaged electrical harness and 2. Vent the air system.
blown fuse. 3. While watching the primary and secondary air
b. Repeat the test. gauges, charge the air system.
4. Both gauges should:
Test (Secondary Service Brake Light) a. Show similar pressure increases.
1. Charge the coach air system and apply the park
brake. b. Have low air warning telltales on until 90 psi is
reached.
2. Turn off the engine.
5. Turn the engine off.
3. Vent the primary service reservoir only.
6. Turn the ignition on.
4. Make a service brake application and ensure that
the brake lights illuminate. 7. With an accurate air gauge, test the primary and
secondary reservoirs. Compare the dash gauge
5. If the brake lights do not light:
readings to the measured pressures.
a. Check for a damaged electrical harness and
blown fuse. 8. While watching the gauges, fan the brakes or vent
the primary and secondary reservoirs.
b. Repeat the test.
9. The low air warning telltales should turn on when
Test (Park Brake Hazard Light) pressure drops to 70 psi. (The dash-mounted low
1. Turn the ignition ON. air telltale and buzzer should activate at 65 psi.)

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 4D-14

AIR HORNS Disassembly

Every 10,000 miles (16,000 km): 1. Remove the nuts and bolts from the two covers.
1. Remove and clean the dirt screens in the horn bells 2. Remove the covers.
(Figure 8). 3. Remove the diaphragms from the body of horn.
2. Perform a system check: 4. Remove the spring contact, springs and the spring
assemblies from the covers of the air horn.
a. With a charged air system, operate the horn. It
5. Remove the horn bells from the body.
should give a loud, clear dual-done report.
b. Coat the delivery port with soap solution. While Inspection
the horn is operating, leakage must not exceed 1. Wash all air horn metal parts in cleaning solvent.
a 1” (25 mm) bubble in one second. 2. Inspect the horn bells. If they are cracked or broken,
replace them.
Removal 3. Inspect the spring and contacts. Replace damaged
1. Vent the air system. parts.
2. Disconnect the air line. Installation
3. Remove the mounting nut and remove the horn. 1. Install the horn in the reverse order of Removal.

20
13 1. Screen
11 12 2. Bell
3
4 3. Contact
8 5 4. Diaphragm
10 7
5. Spring
6. Lock Nut
6 7. Cover
1 8. Seat-Spring
9. Set Screw
2 10. Screw
9 11. Washer
14 12. Nut
13. Bell
15 14. O-Ring
15. Coupling
16 16. Gasket
17. Washer
17 18. Washer
19. Nut
18
20. Body
AIR HORNS
19

FIGURE 8

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 4D-15

SPECIFICATIONS
BRAKE VALVE
Make . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bendix
Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E15R
PARKING BRAKE VALVE
Make . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bendix
Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PP-1
SPRING BRAKE RELAY VALVE
Make . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bendix
Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . R-14
SERVICE BRAKE RELAY VALVE
Make . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bendix
Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . R-12DC
EMERGENCY BRAKE RELEASE VALVE
Make . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bendix
Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . RD-3
SPRING BRAKE VALVE
Make . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bendix
Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SR-1
QUICK RELEASE VALVE
Make . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bendix
Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . QR-1
ABS MODULATOR VALVE
Make . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wabco
PRESSURE PROTECTION VALVE
Make . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bendix
Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PR-4
STOP LIGHT SWITCHES
Make . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bendix

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 4E-1

SECTION 4E
BRAKES
CONTENTS OF THIS SECTION
SUBJECT PAGE
MGM Spring Brakes and Service Chambers
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E-2
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E-4
Inspections and Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E-4
Service Chamber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E-6
Spring Brake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E-7
Haldex Slack Adjusters
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E-9
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E-10
Inspections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E-10
Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E-10
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E-11
Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E-12
Lubrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E-12
Meritor (Rockwell) Slack Adjusters
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E-13
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E-14
Inspections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E-14
Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E-15
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E-15
Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E-16
Lubrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E-16
Q Plus Drum Brake Assemblies
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E-17
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E-18
Maintenance Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E-18
Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E-18
Cleaning and Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E-21
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E-22
Brake Relining . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E-23
Lubrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E-25
Torque Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E-26

Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E-27
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4E-28

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 4E-2

MGM SPRING BRAKES AND SERVICE CHAMBERS

GENERAL DESCRIPTION COMPONENTS

Brake chambers convert air pressure into mechanical Service Chamber
force, actuating the drum brakes. The coach is A service chamber (Figure 1) is a single-diaphragm
equipped with six brake chambers (two per axle): air brake actuator. Compressed air enters through the
inlet port and pushes against the diaphragm,
Axle Brake Chamber compressing the return spring and extending the
pushrod. The pushrod actuates the drum brake via a
Front Axle MGM Type 30 Service Chamber yoke, slack adjuster and S-camshaft. The force applied
Drive Axle MGM MJS 3030 Spring Brake by the pushrod is proportionate to the air pressure in the
Tag Axle MGM MJS 2424 Spring Brake chamber.
Service chambers are identified by the number of
square inches of effective area in their design. (Eg. Type
30 has 30 square inches of effective area.)

INLET PORT RETURN SPRING

MOUNTING STUD
NUT AND LOCK WASHER
DIAPHRAGM

PUSHROD ASSEMBLY
INLET PORT

YOKE

YOKE LOCKNUT
CLAMP RING

FIGURE 1

MOTOR COACH INDUSTRIES

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 Date March 2003 Page 4E-3

Spring Brake The spring brake mechanically engages the parking

The spring brake (Figure 2) has two chambers. The brakes. During normal operation, the piston chamber is
lower chamber is a standard, single-diaphragm service pressurized, and the spring brake is disengaged. To
chamber. The piston-style spring brake chamber is park, air is exhausted from the piston chamber and the
mounted on top of the service chamber and is used for spring forces the pushrod to extend, engaging the
parking. The spring brake chamber operates brakes. The park brake remains engaged without
independently of the service brake chamber. service or park brake air supply. Spring brakes are
An external breather tube connects the non-pressure released when air is supplied to the piston chamber,
volumes of the service and piston chambers. This compressing and holding off the spring.
feature seals the unit from outside air and contaminants. If the air system fails and adequate air pressure is
A manual release bolt allows caging the spring brakes unavailable, the park brakes will engage.
for moving the coach in the absence of air pressure. Stroke Alert: All pushrods have stroke indicators that
are visible when approximately 80% of the stroke is
being used. This feature warns that brake components
require service.

RELEASE BOLT

PARKING SPRING
(POWER SPRING)

PISTON
SPRING BRAKE CHAMBER

BREATHER TUBE

DIAPHRAGM

CLAMP RING

SERVICE CHAMBER

RETURN SPRING

MOUNTING BOLTS

PUSHROD
MGM MJS3030

FIGURE 2

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MAINTENANCE INSPECTIONS AND TESTS

The single diaphragm service chamber is Operation and Pushrod Travel Test
serviceable. The non-pressure plate of the chamber can An operational check for brake chamber pushrod
be removed to service the diaphragm, pushrod and travel at 90 psi (620 kPa) and leakage at 120 psi (830
return spring. kPa) should be performed every 5,000 miles (8,000 km)
or 200 service hours. Test air pressure is measured at the
The spring brake chamber is not serviceable. This
application valve test fittings. Use the following
permanently sealed chamber contains a powerful
procedure:
spring under compression. Do not disassemble the
1. Block the coach. Turn engine OFF. Ensure that
spring brake chamber.
system air pressure is 90 - 100 psi (620 - 690 kPa).
Release park brake.
WARNING 2. Check the following to ensure correct pushrod and
slack adjuster alignment:
S Pushrod is perpendicular to non-pressure plate.
Never disassemble the spring brake S Pushrod, clevis and slack adjuster are in line.
chamber. Serious personal injury or death
S Pushrod is not subject to any side loading.
could result.
S Slack adjuster is at or near 90 degrees to the
Wear eye protection. pushrod during a full service brake application.
3. Apply service brakes, making a full (maximum
During parts of this inspection, one person
pressure) application. The pushrod stroke (Figure
will be in the cab and the other will be
performing tests at the chamber. Ensure that 3) must be at or below the Commercial Vehicle
there is a reliable communication system Safety Alliance Readjustment Limit:
established. TAKE EXTREME CARE to avoid Brake Chamber Pushrod Stroke
personal injury.
Readjustment Limit
Before working on or around a spring Type 30 2.00”
chamber, inspect the chamber for structural
damage. If damage is suspected, do not MJS 3030 2.50”
attempt to cage the brake. The unit will have MJS 2424 2.50”
to be removed from the vehicle and disarmed
following MGM’s recommended procedures.

Never disconnect a pressurized air line. A

Never remove a component or plug unless B C

system pressure has been depleted. Do not Brake Chamber

exceed recommended air pressures.

A -- Fully Applied
B -- Released
C -- Stroke

Formula to calculate stoke: A -- B = C

FIGURE 3
NOTE: If the readjustment limit is exceeded, repair or
adjustment of the slack adjuster or other brake
component is required. Stroke adjustments are made
at the slack adjuster.

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Inspection -- Leak Test 3. Ensure that the breather tube and elbows are in
An operational check for leakage (at 120 psi) should good condition, and that the tube is inserted a
be performed every 25,000 miles (40,000 km). Test air minimum of 1/2-inch into each elbow and secured
pressure is measured at the application valve test with rubber adhesive.
fittings. 4. Ensure that the clamp band is in good condition and
1. With system pressure at governor cut-out level, securely in place. Correct torque is 30---35 lbs-ft
make and hold a full service brake application. (41---47 Nm). Angled, bent or misaligned clamp
Perform a soap bubble test on all clamp rings and band ears indicate over-torquing. Repair/replace if
pushrod seals. Repeat this procedure with the park necessary.
brake applied. Repair any leaks found.
2. Check chamber mounting torques, clamp ring
fastener torques, hose routing clamps and hose
connections. Tighten, clean or replace, as required. CAUTION
Spring Brake Inspection
Inspect the spring brake whenever the equipment is Tighten clamp ring capscrews evenly.
in the shop for regular servicing, or every 50,000 miles
(80,000 km). Follow all safety rules regarding spring
brakes. 5. Ensure that the spring brake is securely mounted to
1. Turn engine OFF. Block the wheels. Visually inspect the bracket. The correct mounting stud nut torque
the spring brake chamber for structural damage is 133---155 lbs-ft (180---210 Nm). Ensure that the
before proceeding. washers are between the nut and the bracket (not
between the chamber and the bracket.)
2. Inspect the exterior surfaces for signs of damage or
corrosion. If found, remove and replace the spring 6. Inspect the non-pressure chamber for damage
brake. around the mounting studs. If found, remove and
replace the unit.
7. Inspect air lines, hoses and fittings attached to the
WARNING chamber. Following safe handling procedures,
remove and replace damaged or leaking parts.
Per CVSA out-of-service criteria, holes or Correct air fitting torque is 25 ft-lbs (34 Nm).
cracks in the spring brake housing render 8. Ensure that the yoke pin is installed and locked in
the unit out-of-service. The unit is potentially place with a cotter pin or approved “clip.” Replace
dangerous and must be handled with
extreme care. damaged or missing parts. Torque the yoke locknut
to 25---35 lbs-ft (34---47 Nm).

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SERVICE CHAMBER 1. Pull pushrod out and clamp with vise or vise grip
Every 100,000 miles (160,000 km) or 3,000 service pliers to relieve internal return spring tension on the
hours (more often for severe service), disassemble the pressure plate.
service chambers. Clean and inspect all parts. 2. Unfasten and remove clamp ring segments.
3. Remove the pressure plate and diaphragm.
Service Chamber Disassembly
4. Release vise or vise-grip clamp on pushrod and
slowly allow spring to expand.
3 5. Remove the clevis yoke and locknut from the
1 pushrod, and remove the pushrod from chamber.
6
4 6. Inspect as follows.
7
5 Service Chamber Parts Inspection
14 1. Wash metal parts in a cleaning solvent and dry.
9 12
2
Reusable parts should be wiped clean. Discard
11 13 breather.
8
2. Inspect parts for excessive wear or deterioration.
3. Check the springs for cracks, distortion or
1. Clamp 8. Spring
corrosion.
2. Nut 9. Nut
3. Bolt 11. Pushrod Assembly 4. Repair or replace parts as required.
4. Diaphragm 12. Nut
5. Pressure Plate 13. Yoke NOTE: Use lube specification S-26 (Dow Corning
6. Plug 14. Lockwasher O-ring lube). See Section 10.
7. Non-Pressure Plate Assembly
5264 NOTE: Replace the diaphragm and return spring in
axle sets. Both the right and left hand chambers of an
FIGURE 4 axle should be changed in order to maintain even
brake application forces. Install new diaphragms or
seals when worn or deteriorated.
CAUTION
Service Chamber Assembly
Cover or tape vise jaws or vice grip pliers to 1. Install new parts and assemble in the reverse order
prevent damaging the pushrod. of the disassembly procedure.
2. Apply shop air and test for air leakage.

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SPRING BRAKE Spring Brake Removal

Manually Uncaging the Power Spring

Uncaging the power spring enables the parking WARNING
brake.
If the spring brake has sustained serious
1. Turn the release bolt clockwise until bottomed structural damage, do not attempt to cage
against the head insert. This normally requires the brake. Use an acetylene torch to cut the
20---25 ft-lbs (27---34 Nm) torque. service pushrod to relieve the pressure be-
2. Important: Secure the release bolt by tightening the ing applied to the slack adjuster. Carefully re-
bolt against the head threaded insert to 50---60 move the unit from the vehicle and disarm the
spring brake. See Disposal.
ft-lbs (68---81 Nm).

Pneumatically Uncaging the Power Spring 1. Turn battery disconnect OFF. Block the wheels.
Inspect brake for damage.
Uncaging the power spring enables the parking
brake. 2. Manually release the spring brake. (Cage the
Power Spring)
1. Apply 90---100 psi (620---690 kPa) air pressure to
3. Remove the cotter pin from the yoke pin, and knock
the parking chamber air port and turn release bolt
out the yoke pin.
clockwise by hand until bottomed against the head
threaded insert. 4. Label and remove the service and spring air supply
lines.
2. Important: Secure the release bolt by tightening the
bolt against the head threaded insert to 50---60 5. Remove the nuts on the mounting bolts.
ft-lbs (68---81 Nm) torque. 6. Remove the chamber from the mounting bracket.

Spring Brake Installation

Caging the Power Spring
Caging the power spring disables the parking brake.
CAUTION
CAUTION Reinstall spring brake in the same orientation
as the original installation. Air connections
must align without bends or kinks in hose.
The breather tube must be positioned on the
Do not exceed the travel of the release bolt. half of the spring brake that faces away from
Do not exceed 74 lb-ft (100 Nm) torque. the road.

Turn the release bolt counter-clockwise to fully 1. Inspect mounting bracket to insure that it is free of
compress (cage) the power spring. See uncaging cracks, burrs and debris.
procedures for torque values. 2. Ensure that both ends of the breather tube are
installed 1/2-inch minimum into the elbows, and
fastened with rubber adhesive or hose clamps.
3. Place unit on the mounting bracket with air ports
aligned to vehicle air lines. Do not use spacers,
washers or shims between the mounting bracket
CAGED and the unit.
4. Install flat washers and lock nuts on mounting bolts.
UNCAGED
Torque to 100---115 ft-lbs (136---155 Nm). Do not
use an impact wrench.
5. Connect yoke to slack adjuster. Install yoke pin
through slack adjuster and yoke, and secure with
cotter pin.
FIGURE 5 6. Ensure that the pushrod is working freely, not bent
or binding and is square to the chamber bottom

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(plus/minus 3 degrees). If necessary, reposition the NOTE: Containers must have openings to expose the
chamber on the mounting bracket or shim the slack head where it is to be cut. Container must be strong
adjuster to the right or left on the camshaft. enough to prevent parts from flying out if the unit
7. Apply sealant to the hose fittings and install air suddenly separates. It is the user’s responsibility to
supply lines into the air ports. Ensure that fittings ensure that the container is safe.
are mated to the correct air inlet port. Torque fittings
2. Position the chamber so the head can be accessed
to 25 ft-lbs (34 Nm).
through the holes in the container.
8. Charge the spring brake with 100 psi (690 kPa).
3. Following applicable safety procedures, use an
Using soap or leak detection solution, inspect for
acetylene gas torch to cut a 1-1/2 to 2 inch (38 to 51
leaks at the supply lines and fittings. If bubbles
mm) diameter hole in the head of the brake to
appear, tighten fittings slightly. Do not exceed 30
expose the power spring. DO NOT cut the power
lbs-ft (41 Nm) torque.
spring.
9. If service clamp band was loosened, apply air to the 4. Repeat the previous step at the opening on the
spring brake and then apply and hold the foot brake opposite side of the container.
to charge the service chamber. Test for leaks
around the circumference of the band. If bubbles
appear, release the air from the chamber and, using
a plastic hammer or rubber mallet, firmly tap the
WARNING
circumference of the clamp band while alternately
tightening the clamp band nuts to 30---35 lbs-ft Do not cut the clamp band bolts before
(41---47 Nm) torque. Repeat the leak test. When no cutting the power spring coils.
more leaks are found, exhaust the air from the
service side of the unit.
5. Completely cut through one of the coils of the
10. Uncage the power spring. exposed power spring. (This may produce a low
11. Exhaust air. pitched “pop” or may cause the brake to jump in the
box.)
Disposal of Old Spring Brake Chambers 6. Repeat the previous step through the opening on
Retired spring brake actuators must be safely the opposite side of the container.
disarmed before disposal to prevent serious personal 7. Ensure that the power spring coils are completely
injury. MGM recommends that the coils of the power cut. Use a screwdriver or similar tool to feel that the
spring be cut with an acetylene torch prior to disposal, as coils are loose inside of the brake. Do Not put
outlined in MGM Brakes Technical Bulletin #031. hands or fingers inside the container. If the coils
1. Place the unit in a specially constructed steel can be moved, the brake is harmless and can be
container. discarded.

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HALDEX SLACK ADJUSTERS

GENERAL DESCRIPTION
The service brake assemblies on some coaches are Pushrod Attachment Arm
equipped with Haldex automatic slack adjusters. Slack
adjusters adjust the drum brakes during service
applications, compensating for normal brake lining
wear.
Haldex slack adjusters are not interchangeable
between axles.

COMPONENTS Adjusting Hex Screw

The Haldex slack adjuster has a pushrod attachment
arm, an adjusting hex screw and an auto-adjust control Control Arm
arm. A pointer-style indicator shows correct installation
and adjustment. The internal mechanisms are not
user-serviceable. Anchor Bracket
(Bracket may vary
Anchor Bracket depending on installation.)
Haldex slack adjusters require an anchor bracket.
The anchor bracket is mounted to the camshaft
chamber bracket. An anchor screw attaches the anchor Anchor Screw
bracket to the control arm.
Clevis
A clevis assembly attaches the slack adjuster to the
FIGURE 6
pushrod. Haldex slack adjusters are connected with a
standard single pin clevis. OPERATION
The slack adjuster connects the brake chamber
pushrod and the drum brake camshaft. The slack
adjuster maintains an optimum clearance between the
brake shoe and the brake drum.
Slack adjusters maintain pushrod stroke within
required limits. If the stroke adjustment limit is
exceeded, slack adjusters or other drum brake
components require maintenance or replacement.

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MAINTENANCE S Observe the adjuster in action. Rotation during

brake application and release indicates
Haldex automatic slack adjusters have sealed automatic adjustment and should decrease on
actuator mechanisms. The internal mechanisms are not each subsequent braking operation.
user-serviceable. Periodic inspection, lubrication and 7. Ensure that all fasteners are secure and
adjustment are required. undamaged. Replace any damaged fasteners.
8. Inspect the control arm and anchor bracket for
integrity. Repair or replace damaged components.
WARNING 9. Lubricate the adjuster. (See Lubrication at the end
of this section.)
Ensure that a reliable communication system Haldex Slack Adjuster Removal
is set up between the person operating the 1. Position the main battery switch to OFF, block the
brakes and the person inspecting the slack
adjuster. Exercise caution when working wheels and release the park brake.
around moving parts. 2. Rotate the adjusting hex screw one full turn
counterclockwise to release the brakes.
3. Remove the clevis pin from slack adjuster arm and
Haldex Slack Adjuster Inspection remove the pushrod.
Every lube interval, brake relining or 5,000 miles 4. Unfasten the anchor screw and disconnect the
(8,000 km) inspect the slack adjusters. control arm from the anchor bracket.
5. Unfasten and remove the hardware retaining the
NOTE: If the coach is under severe service, reduce slack adjuster to the camshaft.
the interval to 4,000 miles (6,000 km) or at reline, 6. Mark spacer washers for reinstallation.
whichever comes first. 7. Slide the slack adjuster and spacer washers off of
the camshaft.
1. Position the main battery switch to OFF, block the
8. Unfasten and remove the anchor bracket from the
wheels.
camshaft extension.
2. Release park brakes. Apply the coach service
brakes and ensure that the over-stroke indicator is
not visible on the pushrod and that the slack CLEVIS PIN
adjuster rotates freely.
3. Release the brakes and ensure that the slack
adjuster and pushrod return to the released PUSHROD
position freely. ATTACHMENT
4. Inspect the bushings in the control arm. Replace the ARM
bushings if worn.
5. Inspect the control arm and anchor screw. If control
arm wear exceeds 1/16” (1.5 mm), replace the
slack adjuster and anchor screw.
ADJUSTING
6. Perform an operational check: HEX
S Manually de-adjust the brakes by turning the CONTROL ARM
adjusting hex screw counterclockwise. A ANCHOR BRACKET
ratcheting sound will occur. If the clutch slips at a LOCK WASHER
ANCHOR SCREW
torque less than 13 ft-lbs (18 Nm), replace the
adjuster.
S Attach a box end wrench to the adjusting hex nut. FIGURE 7

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Haldex Slack Adjuster Installation 9. Install the clevis pin and cotter pin.
1. Position the main battery switch to OFF and block 10. Rotate the control arm away from the adjusting nut
the wheels. until the control arm reaches a positive internal
2. Ensure that the pushrod is fully retracted. Apply air stop. Ensure that the indicator is within the slot.
to release the spring brake. If air is not available, the
spring brake must be caged back.
3. Install the anchor bracket, but do not fully tighten
CAUTION
the fasteners.
4. Apply anti-seize compound to the camshaft splines. If the control position is incorrect, tight
brakes will occur.
5. Install the slack adjuster on the camshaft with the
adjusting hex screw positioned away from the
brake chamber. 11. Position the anchor bracket under the control arm
attachment hole, and fix the control arm in position
6. Check that the slack adjuster lever arm is aligned
with the anchor screw. The anchor screw must
with the pushrod. Use spacer/shim washers as
project a minimum of 3/16” (4.8 mm) into the control
required. A maximum of 0.060 gap/clearance
arm hole.
should be allowed for the slack adjuster.
7. Secure the slack adjuster on the camshaft.
8. Rotate the adjusting hex screw clockwise until the CAUTION
clevis holes line up with the hole on the slack
adjuster’s pushrod attachment arm. Do not use a hammer or prying tool to achieve
hole alignment. To do so will result in improp-
er adjuster installation and damage.
CAUTION
12. Tighten the anchor bracket fasteners, ensuring
Do not force the adjuster into position to align that the control arm does not move.
the clevis holes. Only use the adjusting nut.
13. Adjust the slack adjuster according to the
procedures in Adjustment.

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Haldex Slack Adjuster Adjustment 6. After adjustments are complete, make a full service
NOTE: Release the park brake prior to adjusting. brake application (90 to 100 psi) (620 to 690 kPa)
Wheels must be jacked and able to turn. and check the pushrod stroke. Be sure that it does
not exceed the CVSA readjustment limit.
1. Position main battery switch to OFF and block the
wheels.
Commercial Vehicle Safety Alliance
2. Attach a box end wrench on the adjusting hex
screw. Axle Chamber Readjustment Limit
3. Rotate the adjusting hex screw clockwise until the Front Type 30 2.00”
lining contacts the drum. Drive MJS 30/30 2.50”
4. Rotate the adjusting hex screw counterclockwise
Tag MJS 2424 2.50”
until the backlash is taken up and then 1/2 turn
further. A minimum of 13 ft-lb (18 Nm) is required to 7. Release the brakes and check the lining-to-drum
overcome the internal clutch on the slack adjuster. clearance.
A ratcheting sound will occur. If the clutch slips at a
lesser torque, replace the adjuster. Haldex Slack Adjuster Lubrication
Under normal service conditions, lubricate slack
CAUTION adjusters every 5,000 miles (8,000 km), 150 operating
hours or when brakes are serviced.
Do not use an impact wrench to turn the For severe service, reduce the lubrication interval to
adjusting hex screw. Damage to the adjuster 4,000 miles (6,000 km).
will occur. Lubricate until grease flows out inboard splines. Use
multi-purpose grease, lubrication specification S-16 or
5. With full air pressure, release the spring and service S-19.
brakes and ensure that the installation indicator is
within the slotted area. NOTE: Also see Section 10.

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MERITOR (ROCKWELL) SLACK ADJUSTERS

GENERAL DESCRIPTION COMPONENTS
Some brake assemblies are equipped with Meritor The slack adjusters used on MCI coaches have a
(Rockwell) automatic slack adjusters. Slack adjusters straight arm and clevis. Slack adjusters have an
adjust the drum brakes during service applications, adjusting hex screw and actuator mechanism. A
compensating for normal brake lining wear. separate actuator rod is attached to the clevis with a
Meritor slack adjusters are left or right-handed. These small clevis pin. (See Figure 8.)
slack adjusters are location-specific and must be Internal components of the automatic slack adjuster
positioned correctly to work properly. are not serviceable.

OPERATION
When the brakes are applied, the pushrod extends
SMALL and rotates the slack adjuster, forcing the shoes into the
CLEVIS
PIN brake drum. If normal lining-to-drum clearance is not
present, the actuator rod (also connected to clevis)
LARGE causes the actuator piston to turn the actuator
CLEVIS
PIN ACTUATOR (adjusting sleeve) guided by the pawl teeth. As it turns,
BRAKE AIR ROD
CHAMBER the actuator rotates the adjusting worm gear. The worm
gear turns and rotates the gear wheel, adjusting the
brakes.
PAWL ASSY.
PRESSURE NOTE: Meritor (Rockwell) slack adjusters auto-adjust
RELIEF
CAPSCREW during brake applications.
ACTUATOR
PISTON

HOUSING &
BUSHING
ASSEMBLY

GREASE FITTING
(SHOWN 90˚
OUT OF POSITION)

MANUAL WORM
ADJUSTING
NUT
(END OF WORM)
c0348

FIGURE 8

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MAINTENANCE 5. Check the torque of the clevis jamnut.

S 1/2” - 20 threads require 20 - 30 lb-ft
Automatic slack adjusters have sealed actuator
mechanisms. The internal mechanisms are not S 5/8” - 18 threads require 35 - 50 lb-ft
user-serviceable. Periodic inspection and lubrication is 6. Inspect the clevis pin bushings. Replace worn
required. bushings.
7. Perform adjustment and operational check as in
Adjustment.
WARNING 8. Ensure that all fasteners are secure and
undamaged. Replace any damaged fasteners.
Ensure that a reliable communication system 9. Lubricate the adjuster. (See Lubrication.)
is set up between the person operating the
brakes and the person inspecting the slack
adjuster. Exercise caution when working Inspection -- Clevis Position
around moving parts.
Every 50,000 miles (80,000 km), check the clevis
position.
1. Check the brake slack adjuster position (BSAP).
Meritor Slack Adjuster Inspection
The BSAP is the distance from the brake chamber
Every lube interval or brake relining, inspect Meritor
face to the pushrod clevis pin hole (Figure 10).
slack adjusters.
Coaches are equipped with 5.50” and 6.00” slack
1. Position the main battery switch to OFF, block the adjusters. Ensure that the BSAP matches the table
wheels. value in Figure 10.
2. Apply the coach brakes and ensure that the
2. Adjust the BSAP to ¦ 0.125” of the recommended
over-stroke indicator is not visible on the pushrod
value.
and that the slack adjuster rotates freely.
3. Release the brakes and ensure that the slack
adjuster and pushrod return to the released
position freely.
4. The threads of the pushrod and the clevis must
3.750” and 3.812”
engage for at least 1/2 inch, and not extend through
BRACKET OFFSET
the clevis more than 1/8 inch. (Figure 9) If
necessary, cut the pushrod, install a new pushrod
BSAP ¦ 0.125”
or replace the brake chamber.

SLACK LENGTH
5.50”
6.00”

SLACK ADJ. ¦ 0.125”

SIZE BSAP
5.50” 2.75”
6.00” 2.75”

Correct position of automatic slack adjuster.

FIGURE 10
FIGURE 9

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Meritor Slack Adjuster Removal 4. Install spacer washers as required to align the slack
1. Position the main battery switch to OFF, block the adjuster with the brake chamber.
wheels and release the park brake. 5. Install the slack adjuster on the camshaft with the
2. Remove the pawl assembly. adjusting hex screw positioned away from the
brake chamber.

CAUTION 6. Install spacer washers and snap ring to secure the

slack adjuster on the camshaft.

The pawl must be pulled out before turning NOTE: When installing slack adjuster, ensure that the
the adjusting hex screw. If the pawl is not slack adjuster can rotate to the maximum stroke of the
disengaged, damage to the actuator guide brake chamber. Install the grease fitting and locate so
teeth will occur. that the grease fitting is accessible.

7. Pry pawl and rotate the adjusting hex screw

3. Rotate the adjusting hex screw one full turn clockwise until the clevis holes line up with the pin
counterclockwise to release the brakes. hole in the slack adjuster.
4. Remove the clevis pins.
5. Remove the snap ring from the camshaft.
6. Slide slack adjuster and spacer washers off the CAUTION
camshaft. Mark spacers for correct installation.
Do not force the adjuster into position to
Meritor Slack Adjuster Installation align the clevis holes. Only use the
1. Position the main battery switch to OFF and block adjusting nut.
the wheels.
2. Ensure that the pushrod is fully retracted. Cage the 8. Install the clevis pins and new pin retainer clips or
spring brake. cotter pins. Retainer clips must be positioned
3. Apply anti-seize compound to the camshaft splines. around the side of the clevis pin, NOT around the
end.
NOTE: Install slack adjuster onto camshaft splines so
9. Adjust the slack adjuster. See Adjustment.
slack adjuster hole is in near alignment with clevis pin
hole (within one full turn of the adjusting hex screw). 10. Re-engage pawl.
Slack adjuster may require repositioning on the 11. Uncage spring brake chambers.
camshaft spline for correct adjustment. 12. Lubricate and perform an operational check.

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Meritor Slack Adjuster Adjustment 2. Pry the pawl out approximately 1/32” to disengage.
NOTE: Release the park brakes prior to adjusting the 3. Turn the adjusting hex screw clockwise until the
rear brakes. Wheels must be jacked and able to turn. lining contacts the drum.
1. Position main battery switch to OFF and block the 4. Turn the adjusting hex screw counterclockwise until
wheels. the backlash is taken up, and then 1/2 turn further.
5. Release the pawl to engage.

CAUTION
CAUTION
Actuator mechanisms are fitted with an
actuator guide pawl. The pawl must be Never use an impact wrench on the
pulled out 1/32” before turning the adjusting adjusting hex screw.
hex screw in either direction (Figure 11). If
the pawl is not disengaged, damage to the
pawl and actuator guide teeth will occur. 6. After adjustments are complete, make a full service
brake application (90 to 100 psi) and check the
pushrod stroke. Be sure it does not exceed the
Commercial Vehicle Safety Alliance Limit.

Commercial Vehicle Safety Alliance

DISENGAGE Axle Chamber Readjustment Limit
PULL PAWL
Front Type 30 2.00”
Drive MJS 30/30 2.50”
Tag MJS 2424 2.50”

7. Release the brakes and check the lining-to-drum

clearance.

Meritor Slack Adjuster Lubrication

Lubricate slack adjusters every 5,000 miles (8,000
km) or 150 operating hours or when brakes are serviced.
Apply grease at the grease fitting until it flows out
inboard splines and pawl assembly. Use multi-purpose
grease, lubrication specification S-16 or S-19.
FIGURE 11 NOTE: Also see Section 10.

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Q PLUS DRUM BRAKE ASSEMBLIES

GENERAL DESCRIPTION The brake chamber mounts to the brake chamber
bracket.
Q Plus drum brakes are installed on the wheel ends of
the front, drive and tag axles. They are sized to the axle NOTE: Drive axle brake chamber brackets have a
brake specifications. support lug on the tube. The support lug is bolted to a
similar lug on the axle housing.
Axle Q Plus Brake
Front Axle 16.5” x 6” (419 x 152 mm) Brake Drum
When actuated, the brake shoe linings ride against
Drive Axle 16.5” x 8.625” (419 x 219 mm) the inside circumference of the brake drum.
Tag Axle 16.5” x 6” (419 x 152 mm) Retaining and Return Springs
Two retaining springs hold the shoes in place at the
COMPONENTS anchor pin end. One brake shoe return spring collapses
the brake shoe after actuation.
Q Plus Brake Assembly
Q Plus brakes are air-operated, cam-actuated, dual
shoe drum brakes. Brake Lining
Shoe Return Spring

Lining Shoe Retaining

Spring
Q Plus brake linings are riveted to the brake shoes.
The linings have a thick, tapered design and are made of
high-friction composite material. Brake linings require
regular servicing.
Brake Shoe
Anchor Pins
Two brake shoes are positioned around the inner
diameter of the brake drum. The shoes are held at one
end by two retaining springs. The other end contains two Brake Shoe
camshaft rollers. Brake shoes are retracted to their S-Cam
normal position by a brake return spring.
Spider FIGURE 12
The cast spider assembly holds the brake shoes and
components in position. It is the only brake component
OPERATION
that is rigidly attached to the axle. The spider provides
The brake chamber’s pushrod forces the slack
mounting holes for brake shoe anchor pins, camshaft
adjuster to rotate the brake camshaft. As the camshaft
bracket and attaching bolts.
head turns, the cam rollers ride up and move the brake
Camshaft shoes apart, forcing the brake linings into contact with
There is one camshaft per brake assembly. The the inner brake drum surface. This friction stops the
camshaft rotates inside the tube of the brake chamber coach.
bracket. The slack adjuster is connected to the splined When air is exhausted from the brake chamber, the
end. Two brake shoe rollers are positioned at the cam pushrod and brake shoe return springs return the
head end. Q Plus brakes have S-shaped cam heads. diaphragm, pushrod, slack adjuster and brake cam to
Serviceable components are cam bushings and seals. their released positions.

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 4E-18

MAINTENANCE
WARNING
MAINTENANCE SCHEDULE
Non-asbestos brake linings may contain A schedule for lubrication, inspection, cleaning and
glass, mineral wool, aramid, ceramic or car-
adjustment of brake components must be established
bon fibers. Long-term exposure may cause
serious illness. Avoid creating and breathing based on the specific use and the wear characteristics of
brake dust. the vehicle.

1. Work on brakes away from other operations.

2. Wear an approved respirator. Wear the res-
pirator from the removal of the wheels WARNING
through assembly and clean-up.
3. Do not use compressed air or dry brushing Wear eye protection and a respirator while
to clean brake parts or assemblies. performing brake maintenance.
4. Do not use carcinogenic solvents, flam-
mable solvents or solvents that can damage
brake components as wetting agents.
5. Follow service procedures that minimize air-
borne dust.
S Service brakes in an approved negative WARNING
pressure enclosure, or
S Use a catch basin with water and non- Do not work under a coach supported only by
phosphate detergent to wash brake parts. jacks. Support the coach with safety stands.
Apply the solution with low pressure.
Thoroughly wet components before re-
moving brake shoes. Wipe parts clean with
a cloth, or
S Clean the brake parts in the open air. Apply
a detergent solution with a spray bottle. WARNING
Wipe parts clean with a cloth.
6. Use a vacuum cleaner with a HEPA filter to When working on a spring chamber, follow
clean dust from brake drums, backing the manufacturer’s instructions. The spring
plates and other brake parts. After vacuum- chamber must be caged. Sudden release of a
compressed spring can cause serious per-
ing, remove remaining dust with a damp
sonal injury.
cloth.
7. Grinding and machining must be done in an
area with exhaust ventilation.
8. Clean the work area with a HEPA filter- REMOVAL
equipped vacuum or by wet wiping. Never
used compressed air or dry sweeping. Brake Drum Removal
9. Wash hands before eating, drinking or 1. Position the main battery switch to OFF.
smoking. Work clothes should not be worn
2. Block the wheels not being serviced.
home. Work clothes should be vacuumed
and then laundered separately. 3. Jack the coach and secure with stands.
10. Dispose of discarded linings, used rags, 4. Remove the wheels as outlined in Section 15.
filters, etc. in sealed plastic bags. Consult 5. If the brake has a spring chamber, cage and lock it
local authorities for regulations on waste so that the spring cannot actuate.
disposal.
6. Disengage the slack adjuster by backing off the
adjusting hex screw so that the brake shoes are
fully retracted and the drum clears the lining.
7. Remove the brake drum.

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Printed in Canada.
 Date March 2003 Page 4E-19

Brake Shoe Removal 3. Lift the top brake shoe and pull on the cam roller
Reline brakes when lining thickness is 0.25” (6.35 retaining clip to remove the top cam roller.
mm) at the center. Always reline the entire axle as a set. 4. Lift the bottom shoe to release the tension on the
brake shoe return spring. (Figure 14) Remove the
spring.
WARNING
Brake linings contain non-asbestos fiber.
Avoid creating and breathing dust. See safe-
handling warning earlier in this section.

CAUTION
Linings must be replaced with linings listed
in the MCI Parts Manual only.

1. Mark each shoe to ensure correct positioning FIGURE 14

during reassembly.
5. Rotate the bottom shoe to release the tension on the
2. Push down on the bottom brake shoe and pull the brake shoe retainer springs. (Figure 15)
cam roller retaining clip to remove the bottom cam
roller. (Figure 13)

FIGURE 15

6. Remove the shoe retainer springs and the brake

FIGURE 13 shoes.

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Printed in Canada.
 Date March 2003 Page 4E-20

Camshaft and Slack Adjuster Removal number of spacing washers between the
1. Inspect the cam-to-bushing for play. (Figure 16) automatic slack adjuster and the snap ring to
achieve between 0.005-inch (0.127 mm) and
0.030-inch (0.76 mm) axial free play.
2. Remove the snap ring, washers and spacers from
the camshaft.
3. Remove the clevis from the slack adjuster.
4. Remove the slack adjuster from the camshaft.

WARNING
Wear eye protection. Do not strike steel parts
FIGURE 16 directly with a hammer.

S If radial free play movement exceeds 0.030-inch

(0.76 mm), replace the bushings and seals. 5. Remove the camshaft from the spider.
S If axial end play exceeds 0.030-inch (0.76 mm), 6. Using a driver, remove the camshaft bushings from
remove the snap ring. Add the appropriate the spider and spider bracket.

1 - Shoe and Lining Assembly 18

2 - Shoe Retaining Spring 7
8
3 - Anchor Pin Bushing 15
10 11 16
4 - Brake Shoe Anchor Pin
1
5 - S-Head Camshaft

6 - Camhead Washer 2
7 - Camshaft (Grease) Seal
3 17
8 - Camshaft Bushing
4 14 16
9 - Return Spring Pin
13
10 - Brake Shoe Roller 12
9
11 - Shoe Roller Retainer

12 - Brake Shoe Return Spring

13 - Brake Cast Spider 11 10

8
14 - Chamber Bracket Seal
7
15 - Brake Chamber Bracket
6
16 - Chamber Bracket Capscrew
5
17 - Grease Fitting

18 - Camshaft (thick) Washer Q Plus Brake Components

FIGURE 17

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 Date March 2003 Page 4E-21

CLEANING AND INSPECTION Corrosion Protection

Apply a thin layer of brake grease to parts that have
been cleaned and dried, and will be reassembled

WARNING immediately. Do not apply or allow grease or oil to get on

the brake linings.
If the parts are to be stored, apply rust-inhibitor to all
Solvent cleaners can be flammable, poison- surfaces. Do NOT apply rust-inhibitor to brake linings.
ous and cause burns. Store parts in paper that prevents corrosion and rust.
S Carefully follow the manufacturer’s direc-
tions when using solvent cleaners.
S Wear eye protection and clothing that pro-
CAUTION
tects the skin.
S Work in a well-ventilated area. Inspect all parts before reassembly. Repair
or replace worn or damaged parts. Failure to
S Do not use gasoline or gasoline-contain- do so can result in poor brake functioning or
ing solvents to clean parts. Gasoline can brake failure.
explode.
S Carefully follow the manufacturer’s direc-
tions when using hot solution tanks and al- Parts Inspection
kaline solutions. 1. Check the spider for expanded anchor pin holes
and for cracks. Replace damaged spiders and
anchor pin bushings.
2. Check the brake chamber bracket for broken
Cleaning Rubber or Plastic Parts welds and cracks. Check for correct alignment.
Use soap and water to clean non-metal parts. Do not Replace damaged brackets.
use cleaning solvents or alkaline solutions. 3. Check anchor pins for corrosion and wear. Replace
damaged anchor pins.
4. Check brake shoes for rust, broken welds and
CAUTION correct alignment. Linings must be replaced if 0.25
inch (6.35 mm) or less at the shoe center. Replace
shoes that do not pass inspection.
Do not use hot solution tanks, water or
alkaline solutions to clean ground or 5. Check the camshaft for cracks, wear and
polished parts. Damage to parts will result. corrosion. Check the cam head, bearing journals
and splines. Replace damaged camshafts.
6. Check the brake drums:
Cleaning Ground or Polished Metal Parts S Check the inside of the drum for grooves or
Use cleaning solvent to clean metal parts and scores. If the grooves or scores are deep, replace
surfaces that are ground or polished. Kerosene or diesel the drum.
fuel can be used as cleaning solvents. S Measure the inside diameter (I.D.) of the drum in
several locations with a drum caliper or internal
Cleaning Rough Metal Parts micrometer. If the I.D. is greater than the
Clean rough metal parts with cleaning solvent or with maximum allowed by Meritor, replace the drum.
a weak alkaline solution in a hot solution tank. If using a
hot solution tank, leave the rough parts in the hot Original Diameter Maximum Allowable
solution until they are completely cleaned and heated. 16.50” 16.62”
Remove the rough parts from the hot solution tank and
rinse them with water until the alkaline solution is
removed.
WARNING
Drying
Dry parts completely, immediately after cleaning. Use Under no circumstances should brake drums
compressed air, soft paper or cloth that is free of dirt, oil be used when machined or worn beyond the
and abrasives to dry the parts. Do not use compressed maximum allowable dimension.
air to dry bearings or they will be damaged.

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Printed in Canada.
 Date March 2003 Page 4E-22

INSTALLATION

Camshaft Installation

NOTE: Install new camshaft bushings when installing

a new camshaft.
SEAL LIP
SEAL LIP
1. Torque spider bolts. (Figure 18) SPIDER
BRAKE CHAMBER
BRACKET

FIGURE 20
3. Install the seal and brake chamber bracket onto the
spider. Install the capscrews according to the
Torque Chart.
NOTE: Drive axle brake chamber brackets have a
BOLT SIZE TORQUE support lug on the tube. (Figure 21) The support lug is
lb-ft Nm bolted to a similar lug on the axle housing.
7/16” ---20 60---75 82---101
1/2” ---20 85---115 116---155
9/16” ---18 130---165 177---223
5/8” ---18 180---230 245---311

FIGURE 18

2. Use a seal driver to install new camshaft seals and

new bushings in the spider and the brake chamber
bracket. (Figure 19) Install the seals with the seal
lips toward the slack adjuster. (Figure 20)

FIGURE 21

WARNING
Brake linings contain non-asbestos fiber.
Avoid creating and breathing dust. See safe-
FIGURE 19 handling warning earlier in this section.

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Printed in Canada.
 Date March 2003 Page 4E-23

WARNING CAUTION
Wear eye protection. Use the lining material specified by the
manufacturer. This ensures that the brakes
will perform as designed and meet
regulations.
Reline both wheels of an axle at the same
4. Install the cam head thrust washer onto the time. Install the same linings and drums on
camshaft. Apply O-617-A or O-617-B grease to the both wheels of an axle.
camshaft bushings and journals.
Use rivets that are the correct body
5. Install the camshaft through the spider and bracket diameter, head size and shape, length and
(Figure 22). The camshaft must turn freely by hand. material.

1. Remove brake lining mounting rivets and remove

the old brake linings from the shoe assembly.

CAUTION
When removing rivets from brake shoes,
take care to avoid damaging the holes. Do
not use a chisel to shear rivets off as this
can elongate the holes. If holes are burred,
they should be filed down flush with the
shoe table.

2. Ensure that the new lining and shoe contact faces

FIGURE 22 are clean.
3. Align the rivet holes in the lining with the rivet holes
in the shoe.
Slack Adjuster Installation 4. Install the rivets into the rivet holes following the
1. See Slack Adjuster Installation for Haldex or sequence shown in Figure 23.
Meritor slack adjuster.

BRAKE RELINING

WARNING
Brake linings contain non-asbestos fiber.
Avoid creating and breathing dust. See safe-
handling warning earlier in this section.

FIGURE 23

WARNING A gap of 0.010-inch (0.25 mm) maximum is

acceptable between the shoe and lining along the sides
and ends of the assembly, except between the double
Wear eye protection. web. Between the webs, a 0.025-inch (0.64 mm) gap is
acceptable.

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Printed in Canada.
 Date March 2003 Page 4E-24

Brake Shoe Installation retainer. Press the “ears” of the retainer to permit it
to fit between the brake shoe webs. (Figure 26)
NOTE: Replace springs, rollers, anchor pins and
bushings at each reline.

1. Place the upper brake shoe into position on the top

anchor pin. Hold the lower brake shoe on the
bottom anchor pin. Install two new brake shoe
retaining springs. (Figure 24) WEBS

SQUEEZE
EARS

FIGURE 26

4. Push the cam roller retainer into the brake shoe until
its “ears” lock in the shoe web holes. (Figure 27)
FIGURE 24

2. Rotate the lower brake shoe forward. Install a new

brake shoe return spring with the open end of
the spring hooks toward the camshaft. (Figure
25)

WEB HOLE

PUSH

FIGURE 27

5. Lubricate the brake components according to

Lubrication.

FIGURE 25 Brake Drum and Wheel Installation

Install the brake drum and manually adjust the slack
3. Pull each brake shoe away from the cam to permit adjuster. Install the wheel and torque wheel nuts. (See
space to install the cam roller and cam roller Section 15.)

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Printed in Canada.
 Date March 2003 Page 4E-25

BRAKE BURNISHING 11. With the primary and secondary service reservoirs
After each reline: still empty, apply and hold the emergency release
valve. The brake chamber pushrods on the drive
1. Adjust brake manually.
and tag axles will retract. The emergency release
2. Apply brake ten times (snubs) from 20 to 5 mph (32 valve is momentary and spring-loaded. When force
to 8 km) at regular intervals of approximately 500 is removed from the valve, it will exhaust and the
feet or 0.1 mile (150 m or 0.16 km) without stopping brake chamber pushrods on the drive and tag axles
the vehicle. will apply.
3. After the tenth brake application, make one
complete stop from 20 to 0 mph (32 to 0 km). NOTE: There should be enough air to allow three
park brake overrides before the system is exhausted.
4. Check drum temperatures immediately after
burnishing. Any drums that are significantly cooler 12. Start the coach. Allow the air system pressure to
than the others indicate lack of braking effort on reach governor cut-out (120 psi). Turn the engine
those wheels. Repeat burnishing. off.
5. Allow brakes to cool to ambient temperature. 13. Turn the key to the “run” position, but do not
Readjust all brakes manually. engage the starter.
14. Release the park brakes.
BRAKE FUNCTION TEST
15. Drain the secondary service reservoir.
1. Apply park brake. Chock the tires.
16. Apply the service brake valve. The brake chamber
2. Using the service bake foot vale, make several pushrods on the drive and tag axles will apply.
applications until the pressure gauge on the dash
reads below 80 psi on both needles. LUBRICATION
3. Start coach. Allow the air system pressure to reach Also see Section 10.
governor cut-out (120 psi). Turn engine off.
Camshaft Bushings
4. Turn ignition key to “run,” but do not engage the Lubricate camshaft bushings at 100,000 mile
starter. (160,000 km) intervals. Use multi-purpose grease,
5. Monitor the pressure gauges on the dash for any air lubrication specification S-16. Lubricate more often for
system leakage. Repair any leaks. severe duty applications.
6. Release the park brakes. The brake chamber Lubricate the camshaft bushings through the fitting
pushrods on the drive and tag axles will retract. on the cam bracket. Fill until new grease flows from the
7. Apply service brake valve. The brake chamber inboard and outboard seals. Wipe excess grease from
pushrods on all axles will apply. the outboard side.
8. Drain primary service reservoir (located just behind Grease the camshaft bracket with a hand-operated
drive axle --- “Rear Air” gauge on dash). gun to prevent the seals of the camshaft bushings from
being forced out of the bore during lubrication.
9. Apply the service brake valve. The brake chamber
pushrods on front, drive and tag axle will apply. Brake Assembly Components
10. With primary service reservoir still empty, drain the Brake assembly components such as rollers should
secondary service reservoir (mounted on panel be inspected and lubricated if needed every 10,000
located ahead of front axle --- “Front Air” gauge on miles (16,000 km) and at each brake relining or
dash). When the pressure in the reservoir drops disassembly. Use multi-purpose grease, lubrication
below a nominal 45 psi value, the park brake valve specification S-19.
will auto-eject and the spring brake chamber At these intervals, apply anti-seize compound to the
pushrods on the drive and tag axles will apply. camshaft splines. Use lubrication specification S---23.

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Printed in Canada.
 Date March 2003 Page 4E-26

TORQUE CHART

3 2 1 8
9

6 7 6 9

Brake Torque Chart

Size lb-ft N-m
1 Brake Chamber Bracket 0.500” - 13, Grade 8 90 - 120 122 - 163
0.625” - 18, Plain Nut 150 - 190 203 - 258
0.625” - 18, Lock Nut 130 - 165 176 - 224
M12 x 1.25 80 - 100 109 - 135
2 Hold Down Clip (not on all assemblies) 0.250” - 28 105 - 135 12 - 15
3 Dust Shield (not on all assemblies) 0.312” - 18 12 - 20 16 - 27
0.375” - 16, Grade 8 30 - 50 41 - 68
6 Grease Fitting 0.125” Dryseal 3-5 4-6
7 Brake Chamber Mounting Hex Nuts (Spring 0.625” - 11 100 - 115 136 - 155
and Service Chambers)
8 Pushrod Lock Nut 0.625” - 18 25 - 50 34 - 67
0.500” - 20 20 - 30 27 - 41
9 Camshaft Spacing Washer Add/remove to align slack adjuster with pushrod clevis.
Maximum end play = 0.060 in. (1.5 mm)
Brake Chamber Bracket Support Lug Nut 0.750” - 10 180 - 230 245 - 310
(Drive Axle Only)
Spider to Housing Flange Bolts (Drive Axle) 0.5625” - 18 130 - 165 177 - 223

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Printed in Canada.
 Date March 2003 Page 4E-27

TROUBLESHOOTING
Condition Possible Cause
1. Air pressure drops quickly with A. Leaking brake valve tubing or hose line.
engine stopped and brakes
released. B. Leaking elsewhere in the air brake system.
2. Air pressure drops quickly with A. Leaking brake chamber diaphragm.
engine
i stopped d and
d brakes
b k fully
f ll
B. Leaking brake cylinder or brake valve.
applied
applied.
C. Leaking tubing or hose line.
3. Brakes grab. A. Grease on brake lining --- reline brakes.
B. Brake drum out of round.
C. Defective brake valve.
D. Brake rigging binding.
4. Insufficient brakes. A. Brakes need adjusting, lubricating or relining.
B. Low air pressure in brake system below 80 psi.
5. Brakes apply too slowly. A. Brakes need adjusting or lubricating.
B. Low air pressure in the brake system --- below 80 psi.
C. Brake valve delivery pressure below normal.
D. Excessive leakage with brakes applied.
E. Restricted tubing or hose line.
6. Brakes release too slowly. A. Brakes need adjusting or lubricating.
B. Brake valve not returning to fully released position.
C. Restricted tubing or hose line.
D. Exhaust port of brake valve or quick release valve restricted or plugged.
E. Defective brake valve or quick release valve.
7. Brakes do not apply. A. No air pressure in brake system.
B. Restricted or broken tubing or hose line.
C. Defective brake valve.
8. Brakes do not release. A. Brake rigging binding.
B. Brake valve not in fully released position.
C. Defective brake valve.
D. Restriction in tubing or hose line.
9. Uneven brakes. A. Brakes need adjusting, lubricating or relining.
B. Grease on brake lining --- reline brakes.
C. Brake shoe release spring or brake chamber release spring broken.
D. Brake drum out of round.
E. Brake chamber diaphragm leaking.

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Printed in Canada.
 Date March 2003 Page 4E-28

SPECIFICATIONS
Front Axle Service Chambers

Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MGM
Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Type 30
Effective Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 sq. in.
Pushrod Stroke Readjustment Limit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.00 inches

Drive Axle Spring Brake Chambers

Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MGM
Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MJS 3030
Effective Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 sq. in.
Pushrod Stroke Readjustment Limit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.50 inches

Tag Axle Spring Brake Chambers

Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MGM
Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MJS 2424
Effective Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 sq. in.
Pushrod Stroke Readjustment Limit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.50 inches

Automatic Slack Adjusters

Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Haldex or Meritor (Rockwell)

Length --- Front and Tag . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5 inches
Length --- Drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.0 inches

Front Axle Drum Brakes

Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Meritor
Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Q Plus
Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.5” x 6” (419 x 152 mm)

Drive Axle Drum Brakes

Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Meritor
Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Q Plus
Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.5” x 8.625” (419 x 219 mm)

Tag Axle Drum Brakes

Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Meritor
Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Q Plus
Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.5” x 6” (419 x 152)

MOTOR COACH INDUSTRIES

Printed in Canada.
Date March 2003 Page 4F-1

SECTION 4F
AIR SCHEMATICS

MOTOR COACH INDUSTRIES

Printed in Canada.
 6(59,&( %8//(7,16
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 Date March 2003

SECTION 6
COOLING
A -- RAD & Charge-Air Cooling Module
B -- Cooling System Components
C -- Coolant

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 Date March 2003 Page 6A-1

SECTION 6A

RAD & CHARGE-AIR COOLING MODULE

CONTENTS OF THIS SECTION

SUBJECT PAGE

General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6A-2

Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6A-2
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6A-3
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6A-4
Fan Belt Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6A-4
Fan Belt Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6A-4
Gear Box . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6A-4
Lubrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6A-5
Air Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6A-7
Charge-Air Cooler Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6A-7
Radiator Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6A-12
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6A-13

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GENERAL DESCRIPTION Radiator Assembly

The coolant radiator consists of a core, and upper and
The cooling module performs all of the engine air
lower reservoirs. (Figure 2). The coolant radiator and air
intake and cooling. The module (Figures 1 and 2) is
cooler assembly are mounted together. The radiator’s
cooled with an air operated clutch fan system. It is
core is vertical flow from top to bottom, and maintained
mounted below the belt line on the road side of the
by the engine’s water pump.
coach behind the tag axle.
Coolant circulates through the engine absorbing
The cooling module includes the radiator, charge air
heat. The engine thermostat releases coolant to the
cooler (CAC), cooling fan and fan gear box. The cooling
radiator. Air drawn over the radiator reduces the
module is shrouded and has air seals to increase air
coolant’s temperature. The fan pulls air across the
flow.
radiator through the roadside louvered door, and
discharges it out the rear engine door.
Maximum Allowable Coolant Temperatures
Series 60 Installations . . . . 2003 225_F (107.2_C)
NOTE: The coolant’s maximum temperature must
never be exceeded. Temperatures above this can
cause automatic power-down.

The engine may not produce enough heat to heat the

passenger and driver areas of the coach. An optional
auxiliary heater may be installed to augment the coach
heating system (Section 16).

FIGURE 1

COMPONENTS
Air Cooler Assembly
The air cooler assembly consists of a core, and upper
and lower air boxes. (Figure 1). The air cooler assembly
and coolant radiator are mounted together. The air
cooler’s core is vertical flow.
Fresh air is compressed and heats up in the
turbo-charger. The air flows into the charge-air cooler,
where it is cooled, making it more dense. The cooled
charge-air then enters the intake manifold. The cooling
fan pulls air across the exchanger through the roadside
louvered door, and expels it out the rear engine door. FIGURE 2

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Clutch Fan Assembly two modes: direct and slip. In direct mode, the clutch is
Engine belts drive the fan clutch with its output coupled and the fan is direct drive from the engine
connected to a 90_ gear box. crankshaft pulley. In slip mode, the clutch only transmits
The clutch mechanism is an air-engaged friction plate partial power to the fan. (The fan will run at
design. approximately half speed in slip mode.) The ECM, with
inputs from the ATS and CTS, determines the mode the
The cooling module has a thirty-four inch, nine-blade
clutch operates in. In case of air or electrical power loss,
nylon fan. The fan clutch control system delivers air to
the default is direct mode.
the clutch when required. The automatic fan control can
be tested or by-passed with the test switch at the The fan clutch air control is supplied by a pressure
module’s lower right corner. protection valve from the accessory air system.
Electrical ground for solenoid valves is supplied by the
Cooling System Control ECM.
The DDEC (Detroit Diesel engine control) is the ECM
(electronic control module) that controls all engine
cooling. OPERATION
The engine ECM has inputs from an ATS (air The ECM controls the cooling fan to maintain normal
temperature sensor) and a CTS (coolant temperature engine operating temperatures. Generally, at low ATS
sensor. These sensors are mounted in the air intake and CTS temperatures, the fan clutch will be in slip mode
manifold and the engine head. and at high temperatures, the fan clutch will be in direct
mode. The ECM does not control the cooling fan at fixed
Air Controls set pints. The ECM calculates the rate of temperature
The fan clutch air control receives signals from the changes and maintains engine temperature within a
engine ECM to operate the fan clutch. The fan clutch has range.

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MAINTENANCE 2. Adjust the tensioner.

FAN BELT ADJUSTMENTS 3. When the belt is properly tensioned, tighten the jam
Proper belt tension must be maintained on the fan nuts. Mounting bolt torque should be 55-65 ft.-lbs
drive (Figure 3). Tension the belt to the deflections (75-88 N.m).
shown, when forces shown are applied at mid-span.

FAN DRIVE BELT FAN BELT REMOVAL

10-12 kg/22-28.5 LBS. DIRECTED
PERPENDICULAR IN CENTER OF BELT TO
1. Set the park brake and switch the battery
PRODUCE 13 mm/.5 INCH DEFLECTION
disconnect off.
2. Back off the belt tensioner jam nuts.
BELT TENSION 170 KG/375 LBS NEW
136 KG/3OO LBS USED 3. Relax the tensioner.
4. Remove the belt from the engine crank pulley.
5. Remove the belt from the fan clutch pulley. Twisting
the belt will make removal easier.

A/C COMPRESSOR BELT INSTALLATION

5.4-7.7 kg/12-17 LBS. DIRECTED PERPENDICULAR
1. Installation is the reverse of Removal.
TO PRODUCE 8.6 mm/0.34 INCH DEFLECTION

2. Adjust the belt tension as in Fan Belt Adjustment,

BELT TENSION 91 KG/200 LBS NEW
75 KG/165 LBS USED
noting:
For new belts:
Note:
New belts should be set at the higher rate and re-tensioned af- a. Initially tension the belt to the higher level.
ter a fifteen (15) minute run-in and cool down. Good condition
belts should be set and maintained at the lower tension level. b. After a 15 minute run-in and cool down, tension
the belt to the lower level.
FIGURE 3 For used belts in good condition:
To adjust belt tension: a. Initially tension the belt to the lower level.
1. Loosen the jam nuts on the tensioner (Figure 4).
b. After a 15 minute run-in and cool down, tension
the belt and adjust to the lower level.
3. Check and adjust belts after 200 miles (300 km) and
again after 2,000 miles (3,000 km).

GEAR BOX

Removal
See Charge-Air Cooler Removal for procedure.

FIGURE 4

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LUBRICATION
Initial Service CAUTION
After 100 hours of operation:
1. Drain oil. Loctite is used on all cap screw threads. If
2. Flush out the gear case with a non-flammable screws are removed, Loctite or lockwashers
solvent. must be used for installation. Degrease
threads before applying Loctite.
3. Refill with gear oil.
Lubrication Interval
Every 2500 operating hours or every 6 months:
1. Drain gear oil.
2. Fill with new oil.
If unit is operating in extremely dirty or high or low
temperature environments, reduce this lubrication
interval.
Approved Lubricant
VENDOR LUBRICANT GL-90
AGMA NUMBER 5 EP
ISO-ASTM VISCOSITY GRADE 220
GL-90 is suitable for ambient temperatures of 15 to
125_F (-9 to 52_C) and operating temperatures up to
225_F (107_C). GL-90 contains sulfur phosphorous
antiwear additives. Lubricant must be compatible with
nitrile rubber seals. For operating temperatures above
225_F (107_C) consult MCI Service Parts.
The gear drive is subject to low start up temperatures
and high operating temperatures.
Preventative Maintenance
1. Keep shafts and vent plug clean to prevent damage
to seals and contamination of gear oil.
2. Periodically check for oil leaks.
3. Ensure that coupling, set screws and mounting GEAR BOX
bolts are secure.
4. Check for excessive end play in shafts.
5. Periodically inspect the drive. (Figure 5) See FIGURE 5
Troubleshooting.

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TROUBLESHOOTING
Oil leaking from pinion housing, might be corrected by retightening or removal and recoating with Loctite
caps, cap screws or pipe plugs before tightening. If this does not correct the leaking condition, disas-
sembly will be necessary to replace gaskets.
High internal operation temperature could indicate that unit was being overloaded and should be replaced
(above 200_F) entirely with a larger capacity unit. Damaged bearings or inadequate oil
level can also cause heat build-up.
Oil leaking from seals shaft and/or seals are worn and need replacing or there is excessive
shaft end play. Keep dirt and foreign particles off shafts in the area of the
seals to minimize wear. Note: On initial run of new unit or after a new
replacement of seals, some lubricant leakage is normal for the first few
hours of running time until seals seat against the shafts. If condition per-
sists, seal replacement will be necessary.
Excessive end play of shafts if there is a noticeable (0.002” or more) measurable shaft movement
when couplings are removed and shaft is moved back and forth, it is an
indication of bearing wear.
Excessive backlash might indicate worn gears which often may be readjusted, instead of
replacing.

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AIR CONTROLS tighten all constant-torque hose clamps to 100

Most air control system components require little in-lbs.
maintenance, and some components are not
serviceable. Plastic tubing, fittings, and electrical
switches must be replaced if damaged. WARNING
Every 100,000 miles (160,000 km) or 3600 operating
hours: To prevent possible injury from the test
1. Disassemble. adaptors blowing off, secure the safety
chains on the test adaptors to any
2. Clean. convenient bolt. Always stand clear of the
3. Inspect the solenoid valve. test adaptors while doing this test, and while
4. Check the plunger, spring, piston and seals. the system is pressurized.
5. Replace damaged parts.
4. Double-check all connections to make sure all joints
are tight. Close the air pressure regulator and drain
CHARGE-AIR COOLER ASSEMBLY
the valve before beginning this test.
Periodically inspect the inlet/outlets, air seals, and
fasteners of attaching components.
The only other maintenance or inspection procedure WARNING
that applies to the charge-air cooler (CAC) is leak
testing. Low engine power is a possible cause. A leak
test is the means of determining if the CAC is at fault. NEVER allow the air pressure in the CAC to
exceed 40 psi. Excessive pressure can
NOTE: The CAC must not leak from 30 psi (207 kPa) cause the adaptors to blow off, which may
to 25 psi (172 kPa) in less than 15 seconds. cause personal injury or damage to the
cooler.
Replace the CAC if leakage is excessive. Do not repair
5. Begin the test by slowly opening the air pressure
the CAC: Field repairs void the CAC warranty.
regulator until the test pressure reaches 30 psi.
Charge-Air Cooler Leak Test Close the air pressure regulator when the pressure
To test the CAC, you usually do not need to remove it reaches this point.
from the chassis, but you will need compressed air and a 6. Monitor the pressure gauge, and with a stopwatch
CAC test kit. If your shop does not have this kit, you can determine the rate of pressure decay. It should not
purchase a kit, such as the OTC#5039 Air Cooler drop more than 5 psi in 15 seconds.
Charge Tester, manufactured by SPX Corporation, OTC 7. After testing, open the drain valve to release the
Division, 655 Eisenhower Drive, Owatonna, Mn 55060, pressure.
Phone: (507) 455-7000 8. If the pressure drop exceeded the limit (5 psi),
Following is the procedure for the leak test: recheck all connections.
1. Turn the battery switch off, and set the park brake. 9. Tighten any leaky connections and repeat the test.
2. Remove piping, hump hoses, and clamps from the Obtain at least 3 consecutive readings outside
CAC system. Existing CAC hump hoses and allowable limits before concluding the CAC is faulty.
clamps will be used for this test. If the pressure decay is less than 5 psi in 15 minutes,
3. Set up the test kit as per Manufactured specs. the air cooler is performing within limits and should not
Double clamp all hump hose connections and be replaced.

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Removal 9. Disconnect and remove the coolant radiator inlet

1. Turn the battery switch off, and set the park brake. tube assembly from the radiator inlet. Loosen the
2. Turn off water valves located at the upper right side clamp at the top of the inlet radiator tube, pull it free,
of the engine (Figure 6). twist the tube 180 degrees to the right, pull it up,
swing the top down, to right and remove it
(Figure 8).
RETURN VALVE 10. Disconnect and remove the charge air cooler’s
return and supply hoses at the cooler.(Figure 8).
Flow Open

RAD INLET TUBE

AERATOR LINE

Flow SUPPLY VALVE

closed

FIGURE 6
3. Drain the cooling system (see draining procedure in
sub-section 6B).
4. Drain coolant from auxiliary heater inlet. CAC INLET
5. Open the radiator door (Figure 7).

CAC OUTLET

RAD OUTLET TUBE

FIGURE 8

FIGURE 7
6. Disconnect clutch fan driveshaft at the clutch hub.
7. Disconnect and remove any inlet/outlet coolant
WARNING
piping hanger brackets preventing radiator
removal. When disconnecting the air supply lines,
wear proper eye protection.
8. Disconnect and remove the coolant radiator outlet
tube assembly from the radiator outlet.

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11. Remove the aerator line from the top of the coolant
radiator at the surge tank end, and stow it out of the
way (Figure 9).

FIGURE 11

FIGURE 9 NOTE: Pry bars may be necessary. Use a heel bar

driven between the mounting brackets to loosen the
12. Unfasten and remove the rear upper radiator radiator.
mounting bolt (Figure 10).
14. Pull the radiator assembly out 4 to 5 inches to
remove the lower rad. mount spacer, so the outlet
tube can clear the frame. This will allowing the
radiator assembly to be swung into a servicing
position (Figure 12).
15. With the radiator\air cooler swung out in the
service position unfasten and remove the fan drive
and shroud (Figure 13).
16. Clean seal material from the shrouds and
exchangers if they are damaged or have
deteriorated.
NOTE: Check the inlet/outlet openings for damage,
and straighten them if necessary.
FIGURE 10
Air Cooler Assembly Removal
13. Unfasten and remove the rear lower radiator When the fan drive and shroud have been removed,
mounting bolt from the rear frame support channel the charge-air cooler can be removed from the radiator
(Figure 11). assembly (Figure 14).

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RAD. DOOR

RADIATOR\AIR COOLER ASSEMBLY

Servicing Position

FIGURE 12

RADIATOR\CHARGE AIR COOLER

3.

2.

1.
1. REMOVE COOLANT INLET\OUTLET PIPES. 1.
2. REMOVE FAN DRIVE ASSEMBLY.
3. REMOVE FAN SHROUD.
Fan Drive Assembly Removal

FIGURE 13

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RADIATOR

CHARGE-AIR COOLER
Torque all bolts to 25 ft-lbs.

FIGURE 14. Cooling Module

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RADIATOR ASSEMBLY 2. Install new seal material onto shrouds and

It is essential that the radiator cores be kept free from exchangers if damaged or deteriorated.
corrosion and debris, and that regular maintenance be 3. Position the shroud onto the radiator or air cooler
performed with the other cooling system components. and align the holes to install the fasteners.
See sub-section 6C for further details.
As the radiator assembly has no moving parts, it has Radiator/Charge Air Cooler Installation
no set service interval, aside from that specified for the 1. Reverse the removal procedure’s steps to re-install
coolant. Also inspect the air seals, and fasteners of the radiator or air cooler assembly.
attaching components at the coolant inspection or test 2. Torque mount fasteners to 65 ft.-lbs.
intervals.
NOTE: Check the fan blade-to-shroud clearances,
Radiator Assembly Removal and adjust them if necessary.
Once the fan drive, shroud and CAC have been
removed, the radiator can be disassembled from the
3. Attach clutch fan drive shaft.
module. (Figure 15).
4. Refill the radiator, turn the battery switch on and
Radiator/Charge Air Cooler Assembly start the engine to check for leaks and proper
1. Install Radiator and CAC In reverse of removal. operation.

RADIATOR

Torque 55-85 ft-lbs.

Torque 119 ft-lbs.

FIGURE 15

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SPECIFICATIONS
RADIATOR ASSEMBLY
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Modine
Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Vertical Flow Type
Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Left-hand rear, below belt line
CHARGE AIR COOLER ASSEMBLY
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Modine
Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Vertical Finned-Tube
Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Left-hand rear, below belt line
FAN
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Kysor
FAN CLUTCH
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Horton

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SECTION 6B

COOLING SYSTEM COMPONENTS

CONTENTS OF THIS SECTION

SUBJECT PAGE
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6B-2
Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6B-2
Surge Tank . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6B-2
Engine Water Pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6B-2
Thermostat and Housing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6B-2
Coolant Filter Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6B-2
Draining and Filling System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6B-3
Draining (System) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6B-3
Pressure Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6B-4
System Filling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6B-4
Hoses and Clamps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6B-5
Torque Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6B-7
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6B-8
Service Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6B-9

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GENERAL DESCRIPTION Thermostat Maintenance

Every 200,000 miles (320,000 km) check the
The cooling system components include the water thermostats and the housing seals. Refer to the Detroit
pump, thermostat, oil cooler piping, surge tank and Diesel Maintenance Manual (Sections 5 and 15).
coolant filter.
COOLANT FILTER ASSEMBLY
The engine has an approved coolant filter assembly
COMPONENTS as standard equipment.

SURGE TANK CAUTION

The surge tank is an expansion tank and deareator for
the cooling system (Figure 1). Make-up coolant is
Use only compatible replacement filters and
provided by the surge tank. The surge tank is used for elements. Unapproved filters can damage
coolant filling and is fitted with a sight glass for checking engine components.
coolant level. It has a pressure relief valve in the cap and
a sensor used by the engine ECM.

ENGINE WATER PUMP CAUTION

The water pump circulates engine coolant through
the engine, radiator and the oil cooler. It is mounted on Filter elements containing magnesium
the rear of the engine, and is gear driven. To service the alloys can damage the cooling system.
water pump, refer to the Detroit Diesel Maintenance
Manual (Section 5).

NOTE: Every six months, inspect the drain hole at CAUTION

the bottom of the pump to make sure it is open.
Coolant leakage from the hole indicates seal failure. High chloride coolants are not compatible
with ion exchange filter resins.

THERMOSTAT AND HOUSING

Filter Maintenance
Two modulating thermostats are mounted in one
Change coolant filter elements every 20,000 miles
thermostat housing. The thermostats begin opening at
(32,000 km) or 500 operating hours. Use only Detroit
190_F (88_C) and are fully open at 205_F (96_C). Upon
Diesel approved filters and elements. The filter element
cold engine starting, the coolant flow to the radiator is
is serviced from under the coach, on the left-hand side of
restricted by the thermostat.
the engine.

NOTE: The thermostat housing has provisions for NOTE: Follow the manufacturer’s instructions when
a coolant over-temperature switch. installing new filter element.

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1. SURGE TANK
2. FILLER NECK
3. SUPPORT
4. CAP
5. SIGHT GAUGE
6. HOSE ASSY
7. HOSE ASSY
8. HOSE ASSY
9. FITTING

10. FITTING-HEX

11. AIR VALVE

12. FITTING
13. COOLANT
PRESENT SENSOR
14. OVERFLOW HOSE

FIGURE 1. Surge Tank Assembly

DRAINING AND FILLING SYSTEM 3. To partially drain the system (engine compartment
only), leave the isolation valves closed.
DRAINING (SYSTEM) 4. Slowly release any coolant system pressure and
The cooling system may be completely or partially remove the radiator cap.
drained by using the following procedures. 5. Remove the drain plugs from the engine oil cooler
1. Apply park brake and switch battery disconnect to and the air compressor and open valve at the
OFF. coolant pump.
6. Open the coolant filter drain cocks.

CAUTION 7. Open the central heat core drain cock. Figure 2

Before draining the cooling system, attach a

CAUTION
“Do Not Start” warning to the steering wheel.
Remember to open the flow valves before
running the engine. Closed valves can
2. To drain the entire system, leave the center tunnel cause engine and component damage.
isolation valves open.

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BLEEDER VALVE

FIGURE 2. Central Heater Core Drain

FIGURE 5. HVAC Bleeder Valve

8. If draining the entire system, allow the coolant to
drain from all engine compartment locations
(Figures 3, 4), then open the bleeder valve on the PRESSURE TESTING
central heat core and driver’s heater core If the system is drained, it can be pressurized with air
(Figure 5). and tested for leaks, using the following steps:
1. Using the air valve pressurize the system until the
radiator cap starts to vent air (approximately 10 psi).
2. Check the system for obvious leaks.
3. Leave the system under pressure for 10 minutes.
The pressure should hold with very little loss. (Some
loss through the radiator cap is normal.)
SYSTEM FILLING
The cooling system is filled through the surge tank
filler. Use only approved coolants and recommended
concentrations.
1. Check that all drain valves are closed.
FIGURE 3. Radiator Drain
2. Release any air pressure from the cooling system
and remove the surge tank filler cap.
3. Fill the system with coolant until it reaches the
proper cold coolant level. Opening vents on the top
of the surge tank can speed filling. Do not forget to
close them before operating the coach.

CAUTION
Remember to open the flow valves before
running the engine. Closed valves can
cause engine and component damage.

FIGURE 4 4. Run the engine for 5 minutes, then turn it off.

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 Date March 2003 Page 6B-5

CAUTION CAUTION
Never add cold coolant to a hot engine. The Castings should be clean and free of oil
sudden change in temperature can crack before applying the RTV compound.
the cylinder head or block.

Clamps
Figure 6 shows the clamps used on the coolant
HOSES AND CLAMPS hoses. The initial torque and re-torque values are given
in the Torque Tables.
Inspection
The Oetiker screw clamps close and seal tightly at low
Inspect hoses and clamps at regular intervals. Check
for: torque values. To install Oetiker clamps:
1. Open the screw as far as possible without
1. Collapsed or clogged coolant passages.
disengaging it from the nut.
2. Cracked or worn hoses.
2. Slip the clamp over or around the hose, and engage
3. Loose fittings and connections. the three locking tabs into the windows.
4. Tighten the hose clamps. (See Torque Chart.) 3. Engage the locking tabs in the tightest location
5. Replace any cracked or swollen hoses. When before tightening the clamp.
installing a new hose:
NOTE: Be sure that the tongue is engaged in the
a. Clean the pipe connections. groove area before tightening.
b. Apply a thin layer of a non-hardening sealing
compound. 4. Snug the clamp to the hose, and tighten it two to
three full revolutions to set the clamp seal
c. Use a new hose clamp.
(Figure 7). Do not exceed 18 lb-in (2 Nm) torque on
d. Replace damaged clamps or clamps that pinch Oetiker clamps.
hoses.
NOTE: Leave a 3/16 inch (4 mm) gap between
NOTE: Leakage at the water pump and thermostat D-nuts to allow the clamp to automatically adjust to
housing connections can be caused by rough casting service changes (Figure 8). The locking tab
surfaces. Use Dow Corning RTV-102 compound on engagement may need to be readjusted to attain a
cast surfaces prior to hose installation. proper gap.

Aero Seal Clamp Power Seal Clamp Hi-Torque Heavy Oetiker Clamp
Duty Clamp

FIGURE 6

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Printed in Canada.
 Date March 2003 Page 6B-6

7369 7368

FIGURE 7. Snugging Clamp FIGURE 8. Clamp Adjustment

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Printed in Canada.
 Date March 2003 Page 6B-7

TORQUE CHART

AERO-SEAL AND POWER-SEAL CLAMPS

CLAMP SIZE RANGE INITIAL RETORQUING
RECOMMENDED VALUE
TORQUE
IN-LBS (NSm) IN-LBS (NSm)
RANGE INCHES RANGE MM
1/2 - 7/8 12.7 - 22.2 50 (5.7) 70 - 80 (7.9 - 9.0)
11/16 - 1-1/4 17.5 - 31.8 50 (5.7) 70 - 80 (7.9 - 9.0)
13/16 - 1-3/4 20. - 44.5 50 (5.7) 70 - 80 (7.9 - 9.0)

HI-TORQUE HEAVY-DUTY CLAMPS

100% STAINLESS STEEL
CLAMP SIZE RANGE INITIAL RETORQUING
RECOMMENDED VALUE
TORQUE
IN-LBS (NSm) IN-LBS (NSm)
RANGE INCHES RANGE MM
1-3/4 - 2-5/8 44.5 - 66.7 90 - 100 (10.2 - 13.5) 90 (10.2)
3-3/4 - 4-5/8 95.3 - 117.5 90 - 100 (10.2 - 13.5) 90 (10.2)

OETIKER CLAMPS
CLAMP SIZE RANGE TORQUE TORQUE
IN-LBS NSm
RANGE INCHES RANGE MM
!1-3/4 - 2 44.5 - 50.8 12 - 18 1.4 - 2.0
1-9/16 - 1-3/4 39.7 - 44.5 12 - 18 1.4 - 2.0
2-9/16 - 2-3/4 65.1 - 69.9 12 - 18 1.4 - 2.0
1-1/16 - 1-1/4 27.0 - 31.8 12 - 18 1.4 - 2.0

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 Date March 2003 Page 6B-8

SPECIFICATIONS
THERMOSTATS (SERIES 60 ENGINE)
Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190 - 205_F (88 - 96_C)

TEMPERATURE GAUGE (INSTRUMENT PANEL)

Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Megatech
Operating Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100_-250_F (38_-121_C)

PRESSURE RELIEF VALVE (SURGE TANK FILLER NECK)

Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stant
Pressure Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 psi ( 62 kPa)

COOLANT FILTER (BASIC SERIES 60)

Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (Detroit Diesel Approved)
Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (Spin-On) 46

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 Date March 2003 Page 6B-9

SERVICE TOOLS
SOME OF THE TOOLS USED FOR THE MAINTENANCE PROCEDURES
OUTLINED IN THIS SECTION ARE NONSTANDARD. THEY ARE, HOWEVER,
AVAILABLE FOR PURCHASE FROM MCI SERVICE PARTS. WHERE
PRACTICAL, THEY MAY BE FABRICATED AT THE SERVICE FACILITY.

20 --- 32 SOCKET --- TIGHTENING WATER LINE ELBOWS AT ENGINE

20 --- 60 TOOL --- SIGHT GAUGE GLAND INSTALLATION & REMOVAL

4165

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SECTION 6C

COOLANT
CONTENTS OF THIS SECTION

SUBJECT PAGE
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6C-2
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6C-2
Daily Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6C-2
Periodic Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6C-2
Coolant Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6C-3
Selected Products Supplement Coolant Additive Values . . . . . . . . . . . . 6C-4
Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6C-4
Antifreeze . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6C-5
Corrosion Inhibitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6C-5
Silicate/Phosphate Dropout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6C-6

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GENERAL DESCRIPTION PERIODIC MAINTENANCE

Coolant absorbs heat from the engine. It also absorbs
heat from the transmission fluid and engine oil. Every 10,000 Miles (16,000 km)
The water pump circulates coolant through the 1. Check coolant and inhibitor concentration with a
engine, engine oil cooler, transmission oil cooler, hydrometer or DDC coolant test kit. See Coolant
auxiliary heater and coach heating circuits. Coolant then Testing.
flows through the thermostats to the radiator module
and back to the water pump. Every 20,000 Miles (32,000 km)
1. Check the belts for condition and tension. Tighten
loose belts. Replace worn or frayed belts.

CAUTION 2. Check the water pump operation and installation.

3. Check water pump, thermostat housing and other
components for gasket leakage. Replace leaking
Never exceed the coolant’s maximum gaskets.
temperature. Engine shutdown and damage
can occur. 4. Inspect the radiator and hoses for leakage or
deterioration. Repair or replace damaged
components.
Some major cooling system components are the
5. Replace the coolant filter element. To remove the
radiator module, surge tank, water pump and
filter element, close the two shut-off cocks at the
thermostat. (These are covered in other sections.)
filter mounting head and remove the old element.
The engine is designed to operate with the cooling
system components to regulate coolant temperature. Every 100,000 Miles (160,000 km)
Never exceed the engine’s maximum temperature 1. Drain and clean the radiator cores with
under any engine operating condition. low-pressure air to remove all dirt and sediment.
2. Inspect radiator mounts. Tighten as required.
MAINTENANCE
Every 200,000 Miles (320,000 km)
DAILY MAINTENANCE 1. Drain, clean and inspect the cooling system.
1. With the engine and coolant cold, check the coolant
2. Refill with new coolant and inhibitor solution. (See
level in the surge tank. If low, fill the tank with
Antifreeze Maintenance and Life.)
pre-mixed coolant.
2. Inspect for signs of leakage in the system.
COOLANT TESTING
Always test the antifreeze solution before and after
SIGHT adding water or antifreeze. Use a standard antifreeze
GAUGE tester or a Detroit Diesel coolant test kit. With the coolant
slightly warm, fill and empty the tester several times to
pre-heat it before making the actual test. Keep testers
clean inside and out.
Some testers are only accurate at a specific coolant
COOLANT temperature. Others have a conversion for the actual
FILL coolant temperature.

CLEANING THE COOLING SYSTEM

Only use Detroit Diesel-approved radiator cleaners
and flushing solutions. Exercise caution and follow the
FIGURE 1 manufacturer’s recommendations.

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COLD CLIMATE CAUTIONS

Antifreeze must be used in regions where ambient
temperatures drop below freezing. In harsher climates,
CAUTION
the cooling system requires more frequent inspection.
DO NOT USE:
NOTE: MCI recommends a 50/50 ethylene-glycol Methyl alcohol antifreeze
mixture for most temperatures and operating
conditions. Methoxy propanol antifreeze
Chromate corrosion inhibitors
Sealer additives, such as Stop-Leak
CAUTION Soluble oil additives
Phosphate based inhibitors
If coolant freezes, park the coach in a warm Coolants containing phosphates
location until the coolant thaws completely.
Running the engine while the coolant is frozen High silicate, automotive-type antifreeze
can cause severe engine damage. HVAC coolant

COOLANT REQUIREMENTS Antifreeze Maintenance and Life

Coolant that is properly maintained and protected
Coolant solutions: with supplement inhibitors can be used for two years,
1. Are heat transfer fluids. 200,000 miles or 4000 hours, whichever comes first. At
2. Are corrosion inhibitors. this interval, the antifreeze must be drained, discarded in
an appropriate manner, and the cooling system
3. Inhibit scale and sludge deposits.
thoroughly cleaned.
4. Must be compatible with cooling system hose and
Inspect all cooling system components and make
seal materials.
necessary repairs at this time. Refill the cooling system
5. Provide freeze protection in cold weather and with a recommended ethylene glycol-based antifreeze
boil-over protection during engine operation. and water solution at the required concentration
6. Must be approved by Detroit Diesel. (Figure 2). Add the required DDC-selected cooling
system inhibitors. After filling, run the engine until the
Antifreeze Requirements thermostats open and top off the coolant to the
The first four requirements are satisfied by combining recommended full level. Reinstall the fill/pressure cap.
a suitable water with reliable inhibitors. When freeze
protection is required, use a solution of water and NOTE: Always maintain concentrations at
antifreeze that contains adequate inhibitors. Ethylene recommended levels. Insufficient antifreeze and
glycol-based antifreeze (low silicate formulation) inhibitor can damage cooling system components.
solutions are recommended for year-round use. Overconcentrations of antifreeze or inhibitor can
Antifreeze must meet GM 1899-M or ASTM D4985 result in poor heat transfer, leading to engine
performance requirements. overheating and additive dropout.
Although most antifreezes contain inhibitor
packages, DDC engines require that DDC-selected Proper Coolant Levels
supplement inhibitors be added to the cooling system at Aerated coolant and an air-bound water pump can be
initial fill and maintained at the proper protection level. catastrophic to engine life.
Mix antifreeze/water solutions at the proper Overfilling a cooling system can result in unnecessary
concentration before adding them to the cooling loss of coolant and, in rare cases, engine overcooling,
system. especially during cold weather operation.

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 Date March 2003 Page 6C-4

NOTE: Do not use sealer additives in the cooling Inspect all components that make up the cooling
system. Gumming and gelling material in stop-leak system and make necessary repairs at this time. Refill
additives can plug the cooling passages. the cooling system with a recommended ethylene glycol
base antifreeze and water solution at the required
concentration. Add required DDC-selected cooling
system inhibitors. After filling, run the engine until the
TEMPERATURE thermostats open and top off the coolant to the
C_ F_ recommended full level. Reinstall the fill/pressure cap.
160 320

149 300
SELECTED PRODUCTS SUPPLEMENT
COOLANT ADDITIVE VALUES
138 280
WITH GM6038-M OR ASTM D 4985
127 260

116 240
DDC-SELECTED PRODUCTS SYSTEM
104 220 Min. PPM Max. PPM
94 200 Boron (B) 1000 1500
82 180 Nitrite (NO2) 800 2400
71 160 Nitrate s(NO3) 1000 2000
60 140
Silicon (Si) 50 250
49 120
Phosphorous (P) 300 500
38 100
pH 8.5 10.5
27 80

16 60
Use Penray corporation nitrate test kits to measure
the nitrate concentration. Always follow the
5 40
manufacturer’s recommended test procedures. A
--- 6 20
factory coolant analysis program is also available
--- 18 0 through local DDC distributors.
--- 29 --- 20
WATER
--- 40 --- 40
Water must be distilled, de-ionized or de-mineralized.
--- 51 --- 60 Water must meet specifications in Figure 3. Water
--- 62 --- 80 suitability can be evaluated using Figure 4. Water alone
is not an approved coolant.
0 10 20 30 40 50 60 70 80 90 100
FIGURE 3. SOLIDS IN WATER
ANTIFREEZE CONCENTRATION (% BY VOLUME)
Parts per Grains per
FREEZING POINTS
Million Gallon*
BOILING POINTS Chloride (Maximum) 40 2.5
3490
Sulfates (Maximum) 100 5.8
FIGURE 2
Total Dissolved Solids (Maximum) 340 20
Total Hardness (Maximum) 170 10
Test coolants at each oil change (150 hours or 15,000 Refer to Figure 4 for evaluation of water intended for use in a
miles maximum) to ensure that inhibitor levels are coolant solution.
maintained within acceptable ranges. * 4.5

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 Date March 2003 Page 6C-5

Use only non-chromate corrosion inhibitor

WATER EVALUATION supplement in coolant solutions.

Determine the concentrations of Use antifreeze solutions year-round to provide freeze

chlorides, sulfates and total dissolved protection in the winter and boil-over protection in the
solids in the water. summer.
CORROSION INHIBITORS
Chlorides under 40 ppm Chlorides over 40 ppm A DDC corrosion inhibitor is a water-soluble chemical
and and compound which provides corrosion protection,
Sulfates under 100 ppm Sulfates over 100 ppm
and and cavitation suppression, pH control, and prevents scale.
Total dissolved solids Total dissolved solids All inhibitors deplete through normal operation.
under 340 ppm over 340 ppm Therefore, maintain strength levels by adding inhibitors
as required after testing the coolant.
Determine total Distill, de-mineralize or S pH control chemicals are used to maintain an
hardness of the water de-ionize the water acid-free solution.
S Water-softening chemicals deter formation of mineral
Total hardness Total hardness deposits.
under 170 ppm over 170 ppm
S Cavitation suppression chemicals minimize the
Soften the formation of vapor pockets, preventing erosion of
water cooling system surfaces.
NOTE: It is imperative that a DDC-selected product
Water suitable for use Water suitable for use supplemental inhibitor be added to all DDC engines.
as coolant as coolant
A pre-charge dosage must be used at the initial
Plus inhibitors Plus inhibitors coolant fill and the maintenance dosage used at each
service interval.
3491
DDC-selected cooling system products are
FIGURE 4 nitrate/borate-based formulations. These products
can be used with either water or water-and-antifreeze
solutions. They provide corrosion protection, pH
ANTIFREEZE control, and water softening.
When freeze protection is required, use an ethylene
glycol antifreeze that meets the GM 6038-M formulation. An improperly inhibited coolant can contribute to
An equivalent formulation meeting the 0.15% maximum cavitation erosion. Water pump impellers and cylinder
silicate and GM 1899-M performance requirements is liners are especially susceptible to cavitation erosion.
also acceptable. Ethylene glycol-based antifreeze Non-chromate inhibitors (borates, nitrates, nitrites,
meeting ASTM D 4985 requirements is also acceptable etc.) provide corrosion protection in the cooling system
for use in Detroit Diesel engines. with the basic advantage that they can be used with
The recommended antifreeze concentration is 50%. either a water or water-and-antifreeze solution.
Concentrations below 33% or above 67% should not be Chromates (Not Recommended)
used. Do not use chromate inhibitors in antifreeze solutions.
Methyl alcohol base antifreeze is not recommended Sodium chromate and potassium dichromate are two
because of its affect on the non-metallic components of common corrosion inhibitors. Engines that have
the cooling system, and because of its low boiling point. operated with a chromate-inhibited water must be
Methoxy propanol base antifreeze is not recommended chemically cleaned before adding antifreeze.
due to the presence of fluoroelastomer seals in the Soluble Oils (Not Recommended)
cooling system. Soluble oil is not recommended. It has adverse
NOTE: Although some antifreezes contain inhibitors, effects on heat transfer.
some supplemental inhibitor product must be added Inhibitor System
to coolant system’s initial fill, and maintained at An inhibitor system is a combination of chemical
proper concentrations, to adequately protect the compounds which provide corrosion protection, pH
engine against corrosion. control, and water-softening ability.

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 Date March 2003 Page 6C-6

Non-chromate inhibitor systems are recommended. S Use corrosion inhibitor supplements only as required
These systems can be used with either water or to maintain proper system protection. Test the system
water-and-antifreeze solutions and provide corrosion concentrations before adding inhibitor.
protection, pH control, and water softening. Most Test kits and test strips are available to check engine
non-chromate inhibitor systems have simple on-site coolant for corrosion inhibitor strength level. Do not
tests to determine protection level. use one manufacturer’s test to measure the inhibitor
Inhibitors become depleted through normal strength level of another manufacturer’s product.
operation. Always follow the manufacturer’s recommended test
procedures.
S As much as possible, avoid using what can be called
SILICATE/PHOSPHATE DROPOUT “hard” water when mixing water with antifreeze.
Excessive chemical amounts in the engine coolant
can cause additive dropout. This creates a gel-type Phosphate Removal
deposit that reduces heat transfer and coolant flow. Phosphate can drop out of solution and crystallize on
Dropout may also occur in coolants using extremely heat transfer surfaces and water pump seal faces.
hard water or at unusually high operating temperatures. remove phosphate by flushing the system with water to
re-dissolve the crystals.
Removing Silica Gel Controlling the Amount of Additives in Coolant
If a coach cooling system is suspected to have a The total amount of chemicals in the coolant can be
gelling problem (indicated by engine overheating or controlled to desirable levels by using the referenced
coach underheating), first try to remove the gel in its antifreezes at the needed freeze protection
“wet” condition. Use an alkaline cleaner (Nalprep 2001 concentration, adding DDC-selected inhibitors and
or equivalent) as directed by the manufacturer. This water that meets DDC requirements.
does not allow the silica-gel to dry. If using the cleaner A list of available antifreeze products that meet
once does not correct the problem, repeat the GM-6038M follows:
procedure. If available, ultrasonics can remove the gel Company Product
without damage to cooling system components. Texaco (1) 2055 (was JC-04)
If silica-gel dries inside a cooling system component, BASF Wyandotte (1) 241-7
removing the gel becomes more difficult. The gel tends International Harvester (1)(5) I.H. Antifreeze
to form in low areas of the cooling system, e.g., radiator Old World Trading Co. (1) Full Force Advance
bottom tank or areas within the engine oil cooler. If gel Northern Petro-Chemical (2) All Weather (NPC 220)
can be reached for mechanical cleaning (removal of Dow Chemical Canada (3) 731
radiator bottom tank or “rodding” out a radiator core), Houston Chemical Corp. (4) Security (701)
then that method can be used. Nalco Chemical Co. NALCOOL 2000-Liquid
Nalco Chemical Co. NALCOOL 3000-Liquid
Finally, dried silica-gel may be removed from a
Nalco Chemical Co. NALCOOL 2001-Liquid
cooling system component by removing that
On-Line Cleaner
component from the coach and agitating it in a caustic
Nalco Chemical Co. Nalco 2015 Twin
solution. Use extreme care when handling such caustic Pac-Dry Chemical
solutions. Wear safety glasses and protective gloves . Cleaner/Conditioner
Do not flush the engine cooling system with caustic (1) Generally available in U.S.A.
solutions, because damage can occur to both (2) Generally available within 750-mile radius of Chicago.
metallic and non-metallic components. (3) Generally available in Canada.
(4) Generally available in northeastern U.S.A.
Preventing Silica Gel Formation (5) I.H. antifreeze in Canada has high scale content.

Observing following recommendations should NOTE: Failure to maintain the antifreeze/water and
prevent silica-gel formation: inhibitor coolant mixture at sufficient concentration
levels can damage the engine. Always maintain
S Use antifreeze that meets the GM-6038M formulation,
concentrations at recommended levels.
which limits silicate amount to 0.1% max.
S Never use 100% antifreeze for make-up coolant. Mix Summary of Coolant Requirements
the make-up solution at the same concentration as 1. Always use the recommended antifreeze, inhibitor
the original fill. and water at the proper concentration levels.

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 Date March 2003 Page 6C-7

2. Use only ethylene glycol antifreeze (low silicate S Methoxy propanol-base antifreeze
formulation) meeting the performance specification S Methyl alcohol-base antifreeze
of GM 6038-M (GM 1899-M) or ASTM D 4985
S Sealer additives or antifreezes containing sealer
formulation.
additives.
3. Use an antifreeze solution year-round for freeze and
boil-over protection. Seasonal changing of coolant 11. Use only water meeting specifications in Tables 1
from an antifreeze solution to an inhibitor/water and 2 (Figures 3 and 4). Distilled water is ideal.
solution is not recommended. 12. Always maintain proper coolant level.
4. Pre-mix antifreeze makeup solutions at the proper 13. A cooling system properly maintained and
concentration before adding them to the cooling protected with antifreeze and supplemental
system. inhibitors can be operated up to two years, 200,000
5. Maintain the prescribed inhibitor strength levels. miles, or 4000 hours, whichever comes first. At this
Test the levels at each oil change interval and add interval the coolant must be drained, discarded in a
inhibitor as needed. Do not use another safe manner, and the cooling system cleaned
manufacturer’s test kit to measure the inhibitor thoroughly. Refill the cooling system with a
strength of DDC-selected products. recommended water/antifreeze/inhibitor mixture at
6. Follow Detroit Diesel’s recommendation on inhibitor appropriate concentration level.
usage and handling. Do not mix different base
inhibitor packages.
7. Use only non-chromate inhibitors. WARNING
8. Supplemental coolant inhibitors must be added to
all Series 60 engines after initial fill and must be Never open fill the cap while coolant is hot.
maintained. Open the cap slowly, and only when coolant
9. Change coolant filters at regular service intervals. is at ambient conditions. A sudden release
of pressure from a heated cooling system
10. DO NOT USE THE FOLLOWING can result in possible personal injury from
S Soluble oil the expulsion of hot coolant.
S Chromate inhibitor

MOTOR COACH INDUSTRIES

Printed in Canada.
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 Date March 2003

SECTION 7
ELECTRICAL SYSTEM

A - Electrical Systems
B1 - Bosch T1 Alternator
B2 - Delco Remy 50DN Alternator
C - Starter Motor
D - Alarms & Signals
E - Batteries
F - Lights, Bulb Data and Specifications
G - Relay Modules
H - Electrical Schematics

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Printed in Canada.
 Date March 2003 Page 7A-1

SECTION 7A

ELECTRICAL SYSTEMS
CONTENTS OF THIS SECTION

SUBJECT PAGE
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7A-1
Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7A-4
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7A-6

GENERAL DESCRIPTION modules and the 12 volt driver’s accessory relay module
in the driver’s area. Three circuit breakers are in the
The coach uses a 24V negative ground electrical driver’s defrost blower box, mounted under the right
system. Two 8D batteries are connected in series and front headlight.
their charge is equalized by a 100 amp. electronic A fuse box is on the inboard wall of the battery
equalizer. Two belt-driven alternators with a total rating of compartment. It contains fuses for the engine,
370 amps supply power to the coach electrical system. transmission, HVAC controller, auxiliary heater, door
A group of 9 relay modules perform the switching and controls, relay module coils, and a circuit breaker for the
logic functions necessary for the coach operation. All parcel rack blower.
wiring harnesses in the coach are joined by sealed Each relay module output is rated at six amps. When
multi-pin connectors. a circuit requires more than six amps, the outputs are
An optional battery charger in the battery ganged.
compartment supplies power for in-station lighting and
battery charging when it is supplied with 15 amp., 110 NOTE: Keep all electrical connections clean and
volt power. tight. Inspect all wiring connections regularly.

Fuses and Circuit Breakers

The main power to the coach is controlled by the CAUTION
battery disconnect switch in the battery compartment.
Opening the lockable door allows access to the switch.
Pull the switch for on, and push it for off. (Figure 1). Due to the close proximity of electrical har-
nesses to the aisle floorboard, do not drill
All main electrical circuits are protected either by any holes in the center tunnel area. This
self-resetting circuit breakers fuses, or fusible links. The area is 15 inches wide and runs immediate-
main breakers are on the wall inboard of the battery ly under the coach center aisle for the full
disconnect switch. The breakers feed the 24 volt air length of the coach.
conditioning components the 12 and 24 volt relay

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CAUTION
CAUTION
WELDING PROCEDURES
Improper welding can destroy electrical components. The following precautions and requirements must
be followed before welding on a coach.

1. Welding must be done only by a qualified and experienced person.

2. DO NOT DISCONNECT BATTERY GROUND CABLE
3. Position adequate ground contacts and barriers as close as possible to the weld area and as
required to protect components ( wiring, brake lines, hydraulic lines, etc. ) from damage due to
heat or contact by weld splatter, arcing, or other potentially damaging events associated with
welding.
4. Switch the main battery disconnect switch to OFF.

DISCONNECT THE FOLLOWING:

BATTERY COMPARTMENT:

1. Unplug the battery charger from the AC supply

2. All connectors from the WTEC ECU
3. All connectors from the HVAC controller
4. All connectors from ground module
5. 24 volt cable at battery

ENGINE COMPARTMENT:

6. P-36 and P-50 ( engine adaptor harness )

RH BAGGAGE COMPARTMENT:

7. Four large bulkheads connectors

FRONT JUNCTION BOX

8. All dash connectors

9. Two connectors on relay modules

10. When welding is done, reconnect the items in reverse order. Warn persons in the immediate
area before closing the main disconnect switch.

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EQUALIZER

BATTERY CHARGER

GROUND BLOCK

110V INLET IGNITION

BYPASS
SWITCH

BREAKER PANEL
FUSE BOX

MAIN BATTERY DISCONNECT

SPARE FUSES

BATTERIES

FIGURE 1. Battery Compartment

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COMPONENTS The following switches are mounted on the exterior:

S Engine front start/off;
MODULES S Rear start;
The coach is equipped with solid-state moduleswith S Engine run;
the multiplex system. See section 7G for more detailed
information for these modules. S Radiator fan test;
S Fuel priming pump;
REAR JUNCTION BOX
The rear remote box is located behind the rear engine S Air solenoid valves for the radiator fan drive;
access door and to the upper left of the engine S Engine compartment service lights.
(Figure 2).
The shut-off function for the auxiliary heater is
performed by the engine run switch.
On the underside of the rear junction box is the SAE
J1587 diagnostic connector. This connector allows
diagnostic interface to the following components:
S Detroit Diesel DDEC III;
S Allison WTEC;
S Rockwell Wabco ECAS (Electronically controlled air
suspension);
S Rockwell Wabco ABS (Anti-lock braking system).

FRONT JUNCTION BOX

The front junction box is located behind the sealed
FIGURE 2. Rear junction box front service door (Figure 3) and contains:

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PDM 2
PWR HARNESS

P115
P116
P31

GROUN MOD.
P91, P90, P89 SRM1
FJB PWR
P70 HARNESS

FJB
P72 SRM2 HARNESS

DASH
J1939
CONN.

P110
P27
P33 BLACK PDM 2
P32 PWR CONN.
P28
BLUE SRM 1
PWR CONN.
GRAY SRM 2
PWR CONN.

PWR TRAIN
J1939 COMM.
CONNECTOR

FIGURE 3. Front Junction Box

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WIRING DIAGRAMS FUSE BOX

Wiring diagrams and schematics are located in The fuse box is on the rear wall of the battery
Section 7H. Another set resides in the #1 baggage bay. compartment (Figure 4). It has five types of power
When troubleshooting electrical faults, study the supply lines:
schematics carefully to determine the source and 1. 24 volt battery hot;
current flow in each circuit. After understanding the 2. 12 volt battery hot;
circuit flow thoroughly, do a point-to-point check with the 3. 24 volt switched (after battery switch);
aid of the applicable wiring diagrams. Use a
4. 12 volt switched (after battery switch);
volt-ohmmeter to test any power circuit for shorts or
continuity. 5. 24 volt hot directly from the battery.

BATTERIES
Electrical power is supplied by two SAE type 8D 12
volt wet cell batteries connected in series and rated at
nominal 1350 CCA each. The batteries are mounted in a
sealed housing in the battery compartment that vents to
the exterior of the coach. The batteries perform four
major functions in coach operation:
1. Provide a source of electrical power to crank the
engine during starting.
2. Stabilize coach electrical system voltage as various
FUSE BOX
accessories are switched on and off.
3. For a limited time, furnish electrical current when the
demands of the electrical equipment exceed the FIGURE 4. Fuse Box
output capacity of the alternator.
4. Provide a limited source of electrical power for MAINTENANCE
connected accessories when the engine is not
operating. CIRCUIT TEST EQUIPMENT
Voltmeter
Use a DC voltmeter to check the DC voltage with
CAUTION respect to ground. Connect the negative lead to ground,
and the positive lead to the circuit under test.
Replace the batteries in pairs, following the Ohmmeter
procedure in Subsection 7E. Use an ohmmeter to measure resistance between
two points in a circuit.
For more information on the batteries, see Section 7E.

ALTERNATORS CAUTION
Two engine-powered, belt-driven Bosch alternators
supply electrical power to the coach: Do not use an ohmmeter on energized cir-
cuits. An energized circuit may cause meter
damage or inaccurate resistance measure-
CAUTION ments.

To prevent damage to the unit, always con- Jumper Wire

nect the oil supply when operating the alter- Use a jumper wire in troubleshooting to bypass
nator. certain components or circuit segments where an open
is suspected. A jumper is a length of wire with clips or
For more information on alternators, see Section 7B. terminals used to connect two points of a circuit.

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WARNING
Make sure the jumper wire is sized appro-
priately for the circuit under test.

TROUBLESHOOTING PROCEDURES
For an accurate diagnosis of any electrical problem,
follow a step-by-step troubleshooting procedure:
1. Verify the problem by operating the suspected
circuit. Once the problem area is verified, then refer
to the wiring schematic of the problem circuit.
2. Identify the connections, splices, grounds and
components in the troubled circuit.
3. Systematically test for faulty components,
connections, or grounds to isolate the problem.
When the problem is isolated and a particular element
of the circuit is determined to be the cause of the
problem, make the necessary repair and operate the
circuit to verify the repair.

CAUTION
Use the following precautions to avoid dam-
aging sealed connectors while trouble-
shooting:
1. Do not probe through seals.
2. Do not pierce wire insulation.
3. Use an approved breakout tool.

Open Circuits
An open circuit is one in which power flow or signal
stops because of an interrupted or incomplete circuit
path. An open circuit is caused by an improper ground, a
broken connector, poor terminal contact, a loose or
broken wire, an open or faulty component, or a circuit
breaker or fuse opened by an overload.
Test for an open circuit by using a jumper wire to
bypass a suspected open element. If the circuit operates
with the jumper in place with power is applied, then the
open is in the segment of the circuit bypassed.
Short Circuits
To test for a short circuit, measure the voltage with
respect to ground at the test point.
NOTE: When using an ohmmeter to check for short
circuits, note that stray current may cause the meter
reading to deviate from the actual value.

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SECTION 7B1
BOSCH T1 ALTERNATOR
CONTENTS OF THIS SECTION
SUBJECT PAGE
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7B1-3
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7B1-3
Alternator Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7B1-3
Disassembly and Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7B1-3
Alternator Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7B1-9
Torque Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7B1-12
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7B1-12

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Bearing
Seal
Bearing Collector End
Seal Collector Bearing
Rotor Rings

Drive End A
Cover Drive End
Bearing

Fan

Voltage Air Intake

Regulator Cover
Suppression
Capacitor
A

Collector End
Cover

Rectifier
Assembly

Stator

FIGURE 1

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GENERAL DESCRIPTION Voltage Regulator Removal

1. Remove the regulator fasteners (Figure 3.)
T1 alternators are air cooled, self-excited 16 pole
three-phase generators with synchronous claw-pole
rotors, built-in rectifier diodes and encapsulated
collector rings.

MAINTENANCE
No regular maintenance is required.
1. Periodically check for loose fasteners, torque as Voltage
Regulator
required.
2. Replace the voltage regulator every 100,000 miles.
3. Replace the front and rear bearings every 200,000
miles.
Malfunctioning alternators must be removed for
testing and repair. FIGURE 3

ALTERNATOR REMOVAL 2. Remove the regulator.

1. Use a 3/4” ratchet or breaker bar to rotate the belt
tensioner counterclockwise. NOTE: The regulator must be removed prior to
2. Remove the belt starting from the top alternator further disassembly of the alternator or the brushes
pulley. may break.
3. Remove the alternator fasteners.
Brush Replacement
DISASSEMBLY AND TESTING 1. Measure the length of the exposed brushes, if less
than 0.276” (7mm), replace.
Intake Cover Removal
2. Unsolder the lead and remove the worn brush.
1. Place the alternator in a clamp.
3. Insert the new brush into the regulator and solder
the lead.

NOTE: Use only rosin-core solder.

4. Check the brushes for freedom of movement.

5. Measure the length of the exposed brushes. They
should be 0.630” (16mm).

Noise Suppression Capacitor Test and

Removal
1. Disconnect the suppression capacitor from
terminal B+.
2. Connect a multimeter to the suppression capacitor
lead and the alternator B--- terminal.
3. The capacitance should read between 1.8 and 2.6
FIGURE 2 microfarad. If not, replace the capacitor.
4. Remove the screw that secures the capacitor.

2. Remove the air intake cover fasteners (Figure 2.) NOTE: Short the capacitor on the capacitor mounting
3. Remove the intake cover. strip to prevent accidental discharge.

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Pulley and Fan Removal

1. Use an allen key to hold the rotor shaft and a box
wrench to remove the pulley nut (Figure 4.)

FIGURE 5

Rectifier Assembly Test

FIGURE 4 With a multimeter set to diode test:
1. Connect the negative lead of the tester to the
collector end shield and the positive lead to each of
the stator connection solder joints, no current
should flow.

CAUTION 2. Connect the positive lead of the tester to the

collector end shield and the negative lead to each of
the stator connection solder joints, current should
Do not use an impact wrench to remove the flow.
nut; the alternator bearings may be damaged.
3. Connect the positive lead of the tester to the B+
terminal and the negative lead to each of the stator
connection solder joints, no current should flow.
4. Connect the negative lead of the tester to the B+
2. Remove the pulley and cooling fan from the
terminal and the positive lead to each of the stator
alternator.
connection solder joints, current should flow.
5. Connect the positive lead of the tester to the D+
Separating the Drive Shield and Collector End
Shield terminal and the negative lead to each of the stator
connection solder joints, no current should flow.
1. Scribe a match mark between the drive end and
6. Connect the negative lead to the tester to the D+
collector end shields.
terminal and the positive lead to each of the stator
2. Remove the fasteners (Figure 5.) connection solder joints, current should flow.
3. Slide the drive end shield and rotor out of the If the rectifier assembly fails any test, replace the
collector end shield. assembly.

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Stator Removal and Testing

Test the stator’s resistance while it is still connected to
the rectifier with a multimeter set to read 0 to 0.5 ohms.
1. Connect the test leads between the phase outputs
of the stator. All three phases should read between
0.036 and 0.040 ohms (Figure 6.)

FIGURE 7

Rectifier Assembly Removal

1. Remove the fasteners (Figure 8.)

FIGURE 6

2. Unsolder the stator phase connections from the

rectifier assembly.
3. Open the lead connections and pull the stator leads
from the rectifier eyelets.

Insulation testers apply 80 VAC. When per-

forming this test, take care when handling the
stator or any component connected to the FIGURE 8
stator. Wear insulated gloves and do not 2. Unsolder the W terminal.
touch the work surface or personal injury or
death may result. 3. Remove the nuts fastening terminals B+, B--- and
D+ to the collector end shield.
NOTE: Terminals B+, B--- and D+ are permanently
attached to the rectifier assembly. Terminal W is
4. With an insulation tester, apply 80 VAC to each of attached to the collector end shield.
the stator phase leads with one probe while the
other is on the stator’s exterior (Figure 7.) If there is 4. Remove the rectifier assembly from the collector
any continuity, replace the stator. end shield.

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Dampening Resistor Test and Removal 5. If the bearing is stuck in the end shield:
The W terminal incorporates a dampening resistor. e. Remove the extractor from the bearing.
f. Destroy the bearing cage with a screwdriver.
g. Remove the rollers from the bearing.
h. Insert a spring collet into the bearing outer race.
i. Screw the threaded rod into the spring collet.
j. Slide the receiver cup onto the threaded rod.
k. Screw on the handle and rotate until the bearing
race comes out.
Collector End Shield Bushing Removal
1. Place collector end shield in an arbor press, support
the mounting boss on a mandrel.
2. Place a bushing mandrel on the bushing.
3. Press the bushing out (Figure 11.)

FIGURE 9
1. Connect a multimeter lead to the exterior portion of
the W terminal and connect the other lead to the
other side of the W terminal (Figure 9.) The reading
should be between 3.1 and 3.5 k ohm, if not replace
the W terminal assembly.
Collector End Shield Bearing and Seal
Removal
1. Insert an extractor into the bearing.
2. Screw a threaded rod into the extractor.
3. Slide a receiver cup onto the threaded rod.
4. Screw on the handle and rotate it until the bearing
and seal come out of the collector end shield FIGURE 11
(Figure 10.)

FIGURE 10

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Rotor Removal Collector End Bearing Removal

1. Protect the threaded end of the rotor. 1. Remove the collector end bearing from the rotor
2. Place the drive end shield onto the pressing ring. shaft with a universal bearing puller. Place the jaws
3. Place the pressing ring into an arbor press (Figure behind the bearing not the spacer ring (Figure 14.)
12.) 2. With the bearing puller remove the spacer ring from
the shaft.

FIGURE 14

FIGURE 12 NOTE: All bearings must be replaced any time the

4. Press the rotor out. rotor is removed.
5. Remove the spacer ring from the rotor.
Rotor Inspection
NOTE: All bearings must be replaced any time the 1. With a multimeter, measure the resistance between
rotor is removed. the collector rings of the rotor (Figure 15.) The value
should be 7.5---8.3 ohms.
Drive End Shield Bearing and Seal Removal
1. Remove the fasteners (Figure 13.)

FIGURE 13 FIGURE 15
2. Remove the spacer ring. 2. Apply 80 VAC with an insulation tester to the rotor
3. Remove the bearing from the drive end shield. claw poles and to each collector ring (Figure 16.)

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Insulation testers apply 80 VAC. When per-

forming this test take care when handling
the rotor or any component connected to
the rotor. Wear insulated gloves and do not
touch the work surface or personal injury
or death may result.

FIGURE 17

5. Position the dial indicator to measure the outer

diameter of the collector rings. The maximum
run-out is 0.0012” (0.03 mm) as required, machine
the collector rings down to a minimum of 1.240”
(31.5 mm) diameter. If machining drops the
diameter below the minimum, replace the collector
rings.
Collector Ring Removal
1. Unsolder the rotor leads from each collector ring.
2. With a bearing puller, remove the collector rings one
at a time (Figure 18.)

FIGURE 16

3. Mount the rotor in pair of V-blocks at the bearing

points.
4. Position a dial indicator to measure the outer
diameter of the rotor. The maximum run-out is
0.002” (0.05 mm) as required replace the rotor
(Figure 17.) FIGURE 18

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ALTERNATOR ASSEMBLY 6. Slide the support ring onto the drive end of the rotor.
Ensure that the undercut side of the ring faces the
Rotor Assembly retaining ring on the rotor.
1. Place the rotor, drive end down, in an arbor press. 7. Place the rotor into the drive end bearing (Figure
2. Press the leads for the rotor winding into the slot on 20.)
the shaft.
3. Press a collector ring as far down the shaft as
possible by hand ensuring that the winding leads
are not damaged.
4. Align the slot in the pressing tool with the rotor leads
and press the collector ring as far onto the rotor
shaft as possible (Figure 19.)

FIGURE 20

8. Put the tool onto the end of the rotor and press the
rotor into the drive end bearing until the bearing
seats against the support ring.

Collector Ring End Shield Assembly

FIGURE 19 1. Pack the collector end roller bearing with 0.07---0.09
oz. (2---2.5 g) of grease.
5. Solder one of the rotor winding leads to the collector 2. Place the shield on the arbor press.
ring with rosin core solder.
3. Place the tool into the bearing and press the bearing
6. Clean any solder from the collector ring brush into the shield.
contact surface.
4. Pack the bottom of the collector end housing
7. Repeat steps 3---6 for the second collector ring. bearing bore with 0.07 oz. (2 g) of grease.
8. Press the collector end shield spacer ring onto the
shaft with the tool until the ring contacts the stops
with no gap.
9. Place the radial seal on the shaft.
10. Press the collector end bearing onto the shaft.

Drive End Shield Assembly

1. Insert sealed ball bearing into the drive end shield.
2. Align the bearing cover plate holes with the drive
end shield holes.
3. Insert the screws and torque to 36.3---48.7 in-lbs
(4.1---5.5 Nm).
FIGURE 21
4. Insert the spacer ring into the shield from the fan
side. 5. Coat the sealing lip of the radial lip seal and pack the
5. Place the shield on the arbor press with the fan side seal with 0.07 oz. (2 g) of grease and press the seal
down. into the collector end shield (Figure 21.)

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CAUTION
Do not assemble the alternator with a dry seal
as the seal will fail and contaminate the
brushes and collector rings.
Ensure that there is no excess grease on the
exterior of the seal before installation in the
collector end shield as the brushes and col-
lector rings will be contaminated.

FIGURE 22
5. Install the insulating washer, flat washer and nut to
6. Place the tool into the seal and press the seal into terminal studs B+ and D+.
the shield. 6. Install flat washer and nut onto terminal B---.
7. Place the shield mounting boss on the arbor press. 7. Ensure that the W terminal’s soldering lug is still
properly positioned.
8. Coat the inside of the bore with Molycote.
8. Torque B+ and B--- terminal nuts to 88.5---115 in-lbs
9. Place the sliding bushing on the boss bore. (10---13 NM.)
10. With the tool, press the sliding bushing into the 9. Torque D+ terminal nut to 21.2---28.3 in-lbs
end shield until the bushing is flush with the inner (2.4---3.2 Nm.)
surface of the mounting boss. 10. Install flat washer and second nut and torque B+
11. Insert terminal W into the shield in the location and B--- terminal nuts to 88.5---115 in-lbs (10---13
marked W. Ensure that the terminal’s locating lug NM.)
matches the shield correctly. 11. Install flat washer and second nut and torque D+
terminal nut to 21.2---28.3 in-lbs (2.4---3.2 Nm.)
12. Place the insulator and flat washer onto terminal
12. Install the three screws and torque to 11.5---15
W.
in-lbs (1.3---1.7 Nm.)
13. Install the nut and torque to 36.3---48.7 in-lbs 13. Solder the W terminal’s lug to the rectifier
(4.1---5.5 Nm.) assembly’s solder pad with rosin core solder
14. Install the protective cap onto terminal W. (Figure 23.)

Rectifier Assembly
1. Place flat washers and insulators onto the B+ and
D+ terminal studs of the rectifier assembly.
2. Coat the keyhole shaped opening of the rectifier
with adhesive.
3. Place the rectifier seal on the outside edge of the
keyhole shaped opening on the rectifier. Ensure
that the seal conforms to the shape of the opening.
4. When the adhesive has cured, place the rectifier
into the the collector end shield. Ensure that the
solder lug of the W terminal passes into position on
the rectifier assembly (Figure 22.) FIGURE 23

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Stator Assembly
1. Position the stator on the collector end shield. The
side of the stator with the winding leads should be
closest to the collector end shield.
2. Line up the scribe marks of the stator and end
shield. If either was replaced a new mark should be
scribed across the new part using the replaced
component as a reference.
3. Place each of the stator leads into the
corresponding soldering lug of the rectifier
assembly. After the lead is through the soldering
lug, bend the lead so it forms a U around the lug.
4. Solder each of the stator leads to the rectifier
assembly with rosin core solder (Figure 24.)
FIGURE 25

7. Torque the drive end shield to collector end shield

screws to 21.2---28.3 in-lbs (7.2---9.7 Nm.)
8. Remove the four feeler gauges from between the
stator and rotor.
9. Turn the rotor by hand. The rotor should rotate freely
when turned by hand, if not loosen the fasteners
and repeat steps 6---9.

NOTE: When turning the rotor, listen for rubbing

between the rotor and the stator or stator leads. If any
rubbing sounds are audible, determine the cause and
repair, then return to step 1.
FIGURE 24
10. Remove the alignment pin from the alternator.

Regulator and Capacitor Installation

1. Depress the brush closest to the regulator into the
Rotor and Drive End Shield Installation holder.
1. Position the collector end shield and stator
2. Insert a straightened paper clip into the hole on the
assembly so that the rotor and drive end shield can
regulator to hold the brush in place.
be lowered into place.
3. Pivot the regulator into the opening of the alternator.
2. Guide the rotor and drive end shield assembly until Once the brush holder is inside the alternator cavity,
the rotor shaft enters the bearing. slowly remove the paper clip.
3. Insert the guide pin through the sliding bushing of 4. Align the regulator and alternator mounting holes
the collector end shield and the bushing of the drive while ensuring that the brushes do not break.
end shield.
5. Install the 3 screws and torque to 11.5---15 in-lbs
4. Insert the 4 screws that fasten the drive end shield to (1.3---1.7 Nm.)
the collector end shield, but do not torque. 6. Install the capacitor and torque the screw to
5. Place the alternator assembly in a clamp. 38---54.4 in-lbs (4.3---5.7 Nm.)
6. Insert four 0.012” (0.03 mm) feeler gauges between 7. Connect the capacitor lead to the + spade terminal.
the stator and the rotor at diametrically opposed 8. Install the air intake cover. To not torque the
positions (Figure 25.) fasteners until the alternator is reinstalled.

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TORQUE CHART

63.7-- 85.9 in-lbs

(7.2-- 9.7 Nm)
11.5-- 15.0 in-lbs
(1.3-- 1.7 Nm)

88.5-- 115 in-lbs

(10.0-- 13.0 Nm)
99.5-- 125.4 ft-lbs
(135-- 170 Nm) 26.5-- 30.1 in-lbs
(3.0-- 3.4 Nm)

36.3-- 48.7 in-lbs

(4.1-- 5.5 Nm)

11.5-- 15.0 in-lbs 38.0-- 50.4 in-lbs

(2.4-- 3.2 Nm) (4.3-- 5.7 Nm)

36.3-- 48.7 in-lbs

21.2 28.3 in-lbs 88.5-- 115 in-lbs (4.1-- 5.5 Nm)
(2.4-- 3.2 Nm) (10.0-- 13.0 Nm)

SPECIFICATIONS
ALTERNATOR
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bosch
Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . T1
Current (24 volts) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 Amps @ 1500 RPM
Voltage (Maximum) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Volts
Ground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Negative

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SECTION 7B2
DELCO 50-DN ALTERNATOR
(Used with the Caterpillar C12 Engine)

CONTENTS OF THIS SECTION

SUBJECT PAGE
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7B2-1
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7B2-2
Voltage Regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7B2-7
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7B2-10

GENERAL DESCRIPTION 1. PULLEY NUT

2. ALTERNATOR MOUNTING BRACKET
3. WASHER
The belt driven 50-DN alternators are oil cooled, 4. BOLTS, BRACKET TO ALTERNATOR (3)
5. BOLT, BRACKET TO FRONT COVER
brushless and self-rectifying. All current carrying 6. NUT (3)
members, windings, diodes, and field coils are 7. ALTERNATOR VENT HOSE
8. ALTERNATOR
stationary. The rotor is the only moving component. 9. OIL SUPPLY TUBE
10. ALTERNATOR BRACKET SUPPORT
Alternator installations can be reached through the rear 11. SUPPORT BOLT TO BLOCK
engine access doors and right side service door. 12. BRACKET SUPPORT BOLT
13. OIL DRAIN TUBE CONNECTOR
14. OIL DRAIN TUBE
The alternator is a sealed unit, cooled and lubricated 15. ALTERNATOR PULLEY
by engine oil. The oil inlet is on the diode end cover. The 16. WASHER
17. KEYWAY
oil drains back into the engine crankcase through an oil 18. TEE
19. ELBOW
drain tube. A continuous flow of engine oil flows through
the alternator to lubricate the bearings and cool the
rectifier. The alternator should never be operated with
the oil supply line disconnected.
During operation, the alternator sends 24 volt B+
7 9
current back through the main disconnect switch to
charge the batteries. The charge rate (approximately
27.2 volts) can be adjusted by turning the voltage 18
regulator adjusting screw. See Voltage Regulator --- 19 8
“Adjustment” page 7B2-8, Figures 7, 9 and 10.
Figure 1 shows the 50 DN installation on the 15
10
16
Caterpillar C12 engine and the major installation 1 11
components. 13

3
12
4 14
3
4 17

Figure 1. Alternator Installation -- Caterpillar C12

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MAINTENANCE 5. Release plunger on the gauge handle and read

the tension on the face of the gauge. Repeat the
Access the alternator through the rear engine measurement several times to ensure accuracy.
compartment door, the RH rear side service door and the
access hatch under the rear cross seat. A spring tensioner pulley mechanism assures proper
belt tension. New belts should have a tension of

CAUTION approximately 350 pounds (Detroit Diesel).

NOTE: New belts lose tension rapidly during the
first few minutes of operation. Recheck belt tension
After installing a new or rebuilt alternator, after a 10 minute run-in and 15 minute cool-down
ensure that the wiring between the voltage period. Used belts should have a tension of
regulator and alternator is installed.
approximately 250 pounds (Detroit Diesel).
Do not remove any wires or cables from the
alternator or voltage regulator while the
If the belt tension is less than 200 pounds after the
battery disconnect switch is ON or the
engine is running. run-in period, the tensioner mechanism may need to be
replaced.

The alternator is controlled by a field relay and voltage

regulator. There are three components in the alternator
that require electrical checks: the field winding, the six
diodes and the stator winding (Figure 2).

Alternator Drive Belt Tensioning: Delco-Remy

The ribbed poly-V alternator drive belts of hypalon
material are very sensitive to tensioning. Belt tension
cannot be accurately measured without a tensioning
gauge and a proper measurement. A Burroughs belt
tension gauge (Kent-Moore P/N J41251-B or equivalent)
is recommended by MCI and the engine manufacturer.
To check belt tension follow these procedures.
1. Set park brake, and turn off the battery at the
disconnect switch.
2. Clean any dirt and oil from the alternator drive Figure 2 -- Simplified Alternator Wiring Diagram
belt.
3. Make measurements of the belt tension midway
between the drive pulley and the upper idler, or between CAUTION
the upper idler pulley and the alternator pulley.
4. Fully depress the plunger on the gauge and The alternator is designed for negative
install onto belt. The belt must be positioned over the ground systems. If polarity is reversed, the
hook and under the leg pads to attain a reading. alternator and wiring harness will be
destroyed. Ensure that the alternator and
NOTE: The entire belt width must be supported by battery polarity are negative ground. Do not
the hook and covered by the leg pads. Support ground or short across any of the alternator
legs on gauge should not contact pulleys or any or regulator terminals. Before checking the
other engine components while making alternator, turn the battery disconnect
measurements. Assure that drive belt tension is switch to OFF.
equally distribute during measurement.

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Inspection -- Field Windings to each diode lead and the end frame as shown in
Figure 3 (D, E and F.) Reverse the ohmmeter lead
Check the field windings for shorts and opens with an connections to the same diode to obtain two
ohmmeter. readings.
1. Connect the ohmmeter from the field terminal to
ground. The normal resistance value is 3.0---3.3 NOTE: Ohmmeter readings may vary considerably
ohms at 80_F. when checking diodes, but if both readings are below
300 ohms, or if both readings are above 300 ohms,
NOTE: If the field winding resistance is not in this the diode is defective and should be replaced. A good
range, it should be replaced. See Disassemble. diode will give one high and one low reading.

7. Reattach all leads, torque to 60 --- 80 lb-in.

Inspection -- Diodes
NOTE: When reinstalling diodes, torque to 9---11
Check diodes as follows: ft-lbs. Restake next to the threads in an arbor press
1. Set the main battery disconnect switch to OFF. with an 1/8 inch round punch. Press the punch with
2. Remove the pipe plug from the end housing to drain gradual pressure; do not strike. The shock may
the engine oil from the rectifier. damage the diodes.
3. Remove the diode cover from the end housing.
8. Replace the diode cover and screws.
4. Detach the diode leads from the DC terminal and
relay R1 terminal, then disconnect the end frame 9. Replace the oil plug.
mounted diode leads from the supports.
Inspection -- Stator Windings
NOTE: Use an analog ohmmeter with a 1-1/2 volt cell.
Select a range where the 300 ohm value lies within the (Check with diode leads disconnected.)
middle third. Checked for open circuits and shorts with an
ohmmeter as follows (Figure 4):
5. Check the three diodes mounted in the diode 1. Connect the ohmmeter leads to two pairs of diode
supports for shorts or open circuits. Connect the supports as shown in Figure 4 (A and B.) The
ohmmeter to each diode lead and to each support ohmmeter should show a low resistance. If a high
as shown in Figure 3 (A, B and C.) Reverse the resistance is measured in either check, the stator
ohmmeter lead connections to the same diode to windings are open.
obtain two readings.

A B
A B C

Do Not Ground

C
D E F
Figure 4 -- Stator Winding Inspection
Figure 3 -- Diode Inspection (Sample)
2. Connect the ohmmeter leads to the diode support
6. Check the three diodes mounted in the end frame to check for grounds. If a low resistance is
for shorts or open circuits. Connect the ohmmeter measured, the stator winding is grounded.

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Output Check 2. Disconnect the electrical wiring at the diode end

frame.
IMPORTANT: The alternator is controlled by a 3. Disconnect engine oil supply and return lines.
field relay and voltage regulator. At voltages above
31.5 volts DC (for 0.5 seconds), the main PC NOTE: Leave alternator oil distributor tube attached.
board’s over-voltage circuit will shut down all A new tube is provided with the replacement
output from the 50-DN alternator by energizing the alternator.
field relay and turning on the “RED” over-voltage
LED. The board is reset by turning ignition “OFF” 4. Remove jack screw tensioner and remove the drive
and “ON” again. Note the voltmeter after resetting belt.
to determine if alternator is producing over-voltage 5. Remove the four mounting bolts and lift alternator
conditions. Correct voltage output should be 27.2
volt DC. off mounting bracket.

Disassemble
CAUTION Refer to Figure 6 --- “50 DN Alternator Components”,
page 7B2-6 to identify the components for disassembly.
1. Remove the pulley hex nut and pulley from the
Do not operate the alternator at outputs
splined shaft.
greater than 100 amps for 15 seconds
without circulating oil. The alternator will 2. Remove the nuts and washers from the DC terminal
overheat and damage the winding and on the diode end frame.
diodes. 3. Separate the diode cover (1) from the diode end
frame (2) by removing the mounting screws.
The alternator may be bench tested without 4. Disconnect all diode leads.
circulating oil, providing the output is limited to 100 amps 5. Remove the nuts and washers attaching the diode
or less. The alternator may be checked without support brackets (54) to the diode end frame and
circulating oil at outputs exceeding 100 amps for less the stator stud terminals (12).
than 15 seconds (Figure 5). 6. Remove the diode support brackets from the diode
end cover.
7. Mark the positions of the drive end frame and diode
end frame with respect to the stator assembly so
that the parts can be reassembled in the same
position.
8. Remove the diode end frame (2) and field assembly
(3) from the stator assembly (4).
9. Separate the field assembly from the diode end
frame.
10. Remove the drive end frame (6) and rotor (5) from
the stator assembly.
11. Press the rotor shaft out of the drive end frame.
12. Remove the rotor plate (24) from the drive end
frame.
13. Pull the inner and outer bearings (7 and 8) from the
Figure 5 -- Alternator Output Check Set-Up drive end frame.

Remove NOTE: Torque the outside nut on the DC output

terminal to 30---35 ft-lbs. The lower nut should be
1. Turn the main battery disconnect switch OFF. secured while torquing the top nut.

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Assemble Torque fasteners to specification.

2. Tension the drive belt See heading: --- “Alternator
Refer to Figure 6 --- “50 DN Alternator Components”,
Drive Belt Tensioning” -- Page 7B2-2.
page 7B2-6 to identify the components for assembly.
1. Press the inner bearing (7), spacer (9) and outer START-UP
bearing (8) into the drive end frame (6). Press
After installing an alternator, perform the following
against the bearing’s outer race only.
procedure to fill the oil galleries and prevent the
2. Install the rotor plate (24) over the bearings. alternator from overheating.
3. Press the rotor shaft into the drive end bearings. 1. Turn battery disconnect switch OFF.
Support the rotor (5) from the inside base of the
2. Disconnect and remove the field relay from rear
shaft to avoid deforming the bronze ring. Press
junction box.
against the bearing’s inner race only.
4. Assemble the remaining components by reversing 3. Turn all dash switches OFF, and place battery
the disassembly. disconnect switch to ON.
5. Slide the pulley onto the splined end of the shaft, 4. Turn the master switch ON, and start the engine.
hold the pulley with a non-slip device (such as a 5. Run the engine for five minutes to ensure that
rubber snubbing vice) and torque it to 200 ft-lbs. engine oil has circulated into the alternator.
6. Stop the engine, turn master switch OFF and turn
Install battery disconnect switch OFF.
1. Install the alternator by reversing the removal. 7. Reinstall field relay in rear junction box.

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1. Cover - DE 19. Diode Support Bracket 38. Diode Mounting Nut

2. Frame - DE 20. DC Terminal Washer 39. Bearing Retainer Plate Screw
3. Field Assembly 21. Stator Terminal Washer 40. DE Bearing Retainer Plate Screw (inner)
4. Stator & Frame Assy 22. DC Terminal O-Ring 41. DE Frame & Cover Screw
5. Rotor Assy 23. Field & Relay Terminal O-Ring 42. DE Cover Washer
6. Frame - Drive End 24. DE Rotor Plate 43. DE Cover Screw & Washer
7. Ball Bearing - Inner DE 25. DE Frame Pipe Plug
8. Roller Bearing - Outer DE 44. Field Mounting Screw
26. DC Terminal Sleeve 45. Diode Lead Screw & Washer
9. Spacer - Bearing 27. Field and Relay Terminal Sleeve
10. Diode - In-Frame 46. DC Terminal Washer
28. DE Frame & Field Terminal Lockwasher 47. DC Terminal Bushing Washer
11. Field Stud Terminal 29. Field Mounting Lockwasher 48. Field Terminal Washer
12. Stator Stud Terminal 30. DC Terminal Lockwasher 49. Field & Relay Terminal Bushing
13. Relay Terminal and Lead Assy 31. DC Terminal Lockwasher Washer
14. DC Terminal Stud 32. Field Terminal Lockwasher 50. Stator Terminal Washer
15. Stator and DE O-Ring 33. Field and Relay Lockwasher 51. Stator Terminal Washer
16. Bracket Spacer 34. Relay Terminal Lockwasher 52. Gasket
17. Shaft Washer 35. DC Terminal Nut 53. Diode Support Bracket Stud
18. DE - Shaft Nut 36. DC Terminal Nut Assembly
37. Field & Relay Terminal Nut 54. Diode Support Bracket

Figure 6 -- 50 DN Alternator Components

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(SECTION 7B2)
VOLTAGE REGULATOR
CONTENTS OF THIS SECTION
SUBJECT PAGE
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7B2-7
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7B2-8
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7B2-9
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7B2-10

GENERAL DESCRIPTION The voltage regulator is mounted in the battery

compartment. The cover contains a hole through which
The voltage regulator for the 50-DN (Figure 7) is a the regulator adjusting screw can be reached.
potted, temperature-compensated unit with no The regulator limits the alternator voltage to a pre-set
user-serviceable parts. The terminals are: value by controlling the alternator field current. The
a. Ignition (IGN) voltage at which the alternator operates is determined
b. Battery (BAT) by the regulator adjustment. Once adjusted, the
alternator voltage remains constant.
c. Field (FLD)
A typical wiring diagram of a negative ground system
d. Ground (GND). is illustrated in (Figure 8). This diagram shows only the
basic charging system components.
FIELD TERMINAL
GROUND
TERMINAL
ADJUSTING TERMINAL

BATTERY IGNITION
TERMINAL TERMINAL

Figure 7 -- Voltage Regulator

Figure 8 -- Simplified Charging System Diagram

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MAINTENANCE REGULATORVOLTMETER

This regulator connects to the electrical system through GFBI

the Ground (G); Field (F); Battery (B) and Ignition (I) IGNITION SWITCH
terminals. A typical wiring diagram of a negative ground
system and its components has been provided (Figure AMPMETER
8). This diagram shows only the basic charging system VOLTMETER
components, and not other components.
F R1 RELAY
+
-
Adjustment: Voltage Regulator:
Delco-Remy BAT -
+

Before making any changes in the regulator’s BATTERIES

ALTERNATOR G0537
adjustment, ensure that the batteries are fully charged
(approximately 20 minutes running time), and that water G0537 Figure 9. Checking or Setting Regulator
level is correct. Quickly check the battery condition
through the Vanner’s charging circuit to assure that both 5. If the voltage is not within this limit the regulator
are evenly charged. To check and set the voltage on the should be reset. Make any necessary changes by
regulator follow this procedure. turning the adjusting screw (Figure10). This will change
1. Disconnect, tape and secure the BAT wire from the the voltage to meet the needs of the vehicle as dictated
auxiliary (pony) alternator (if equipped). by operating conditions and/or ambient temperature.
2. Connect a voltmeter across the POS and NEG 24 6. Replace the wire on the auxiliary (pony) alternator’s
volt terminals on the batteries (Figure 9). BAT wire (if removed).
7. If the voltage cannot be adjusted to the desired
3. Operate the engine at fast idle with the air value, make a complete service check of the alternator. If
conditioning turned off and the headlights and and the alternator checks out, proceed with the
interior lights turned on to produce a load of about 50 to troubleshooting procedure that follows.
60 amperes.
4. The voltage measured at the batteries should be
steady at approximately 27.2 volts (plus or minus 0.3
volts). This is the factory setting that will be used on most
vehicles.

NOTE: Where maintenance-free batteries are

used, a slightly higher regulator voltage setting
may be allowed. The absence of any gassing and
the continuous appearance of the green dot in the 5323
built-in hydrometer should indicate that the
regulator’s voltage setting is satisfactory. 5323 Figure10. Adjusting Voltage Regulator

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TROUBLESHOOTING 8. Replace the BAT wire from the auxiliary alternator (if
The usual symptom of trouble in the regulator circuit is removed).
undercharged or overcharged batteries. An improper Over-Voltage Battery Symptoms
voltage regulator setting can cause either condition.
IMPORTANT: The alternator is controlled by a
Undercharging field relay and voltage regulator. At voltages above
The alternator is not charging sufficiently when the 31.5 volts DC (for 0.5 seconds), the main PC
dash voltmeter reading is low, the lights are dim, the board’s over-voltage circuit will shut down all
starter solenoid chatters, the battery indicator is on output from the 50-DN alternator by energizing the
when the engine is running or the starter cranks slowly or field relay and turning on the “RED” over-voltage
LED. The board is reset by turning ignition “OFF”
does not crank at all. and “ON” again. Note the voltmeter after resetting
Overcharging to determine if alternator is producing over-voltage
conditions. Correct voltage output should be 27.2
The alternator is overcharging when battery volts DC.
electrolyte levels are low, lights burn brightly or burn out,
the dash voltmeter is reading high, the batteries are hot If an over-charged battery symptom exists and turning
or smell bad or the battery indicator light is on when the the adjusting screw does not adjust the voltage, use the
engine is running. following procedure:
1. Disconnect the BAT wire from the auxiliary
Under Voltage Battery Symptoms
alternator as before.
If an under-charged battery symptom exists and turning
2. Operate the engine at fast idle with the air
the adjusting screw does not adjust the voltage, use the
conditioning turned off and the headlights and and
following procedure:
interior lights turned on to produce a load of about 50 to
1. Disconnect the BAT wire from the auxiliary 60 amperes.
alternator (if equipped).
3. Check the voltage between the regulator’s
2. Make sure the ignition key is off. “Battery” and “Ground” terminals. A voltage of
3. Turn the master switch on, and place the positive approximately 27.2 volts (plus or minus 0.3 volts) should
voltmeter lead at the regulator’s “Ignition” terminal. The be present. If not, reset the voltage at the regulator.
reading should be the same as the “Battery” voltage. If 4. Remove the regulator’s “Field” wire and check
so, go on to step #4. If the voltage is low or zero, check voltage at the terminal. Compare this reading with the
the switches and wiring harnesses between the battery voltage at the “Battery” terminal. If the regulator’s “Field”
and the regulator’s “Ignition” terminal for opens an loose voltage is more than 1 volt above the battery voltage,
connections. Repair and recheck the voltage to verify check the wires between the battery and the regulator
the repair. for shorts.
4. With voltage now at “Ignition” terminal, place the
voltmeter positive lead at “Field”. This reading should be NOTE: The voltage of the regulator’s field wire
within 3 volts of the “Battery” terminal’s voltage. If so, should be zero when removed. If the voltage is any
then check the “Field” voltage at the alternator’s higher, check for a field wire short to a B+ power
terminal. source.
5. If the alternator’s “Field” voltage is near zero, find
5. If the voltage still cannot be adjusted and/or
the open in the wire from the regulator to the alternator’s
corrected, replace the regulator and recheck the
“Field” terminal and repair it. Recheck the voltage to
alternator’s output.
verify the repair.
6. If the voltage at regulator’s “Field” terminal is less Voltage Drift Test
than 5 volts of “Battery”, remove the wire from the 1. Check and set the voltage regulator to 27.2 volts
terminal and recheck the voltage at regulator. (plus or minus 0.3 volts) with the coach running at fast
idle, the air conditioning turned off, and with the
NOTE: If it is now within 3 volts of the battery’s headlamps on.
voltage, check the field wire for grounds and/or the
2. Turn on the A/C switch and slowly open the engine
alternator field for shorts or grounds. Refer to
throttle until full throttle is reached.
sub-section 7B for properly checking the
alternator. 3. If the voltage rises above 27.8 volts, reset or replace
the regulator.
7. If the voltage is still less than 5 volts, replace the 4. If the voltage regulator reading does not exceed
regulator. 27.8 volts, it may be left in service.

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SPECIFICATIONS
ALTERNATOR
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Delco-Remy
Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50-DN
Current (24 volts Minimum Recharging) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2---8.0 Amps
Current (24 volts Hot Output) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 270 Amps at 80_F Ambient
Voltage (Maximum) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Volts
Drive RPM (Approximate) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3000
Ground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Negative

TORQUE CHART
Diode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9---11 lb-ft
Diode Leads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60---80 lb-in
DC Output Terminal (Top nut when double nutted) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30---35 lb-ft
Field Assembly Mounting Screws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22---28 lb-ft
Shaft Nut (Pulley) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200 lb-ft
Alternator-to-Bottom Mounting Bracket . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 ft-lbs (94 N.m)
Alternator Mounting Bracket Strut . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 ft-lbs (54 N.m)

REGULATOR (24-VOLT)
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Delco-Remey
Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Solid State
Voltage Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .External Screw

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SECTION 7C
STARTER MOTOR
CONTENTS OF THIS SECTION
SUBJECT PAGE
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7C-2
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7C-2
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7C-2
Lubrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7C-2
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7C-2
Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7C-2
Starting Motor Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7C-3
Disassembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7C-4
Brushes and Holders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7C-4
Armature (Testing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7C-4
Field Coil Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7C-5
Solenoid Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7C-5
Bushing Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7C-6
Clutch Drive Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7C-6
Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7C-6
Pinion Clearance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7C-7
Starter Lockout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7C-7
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7C-8

MOTOR COACH INDUSTRIES

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 Date March 2003 Page 7C-2

GENERAL DESCRIPTION Remy No. 1960954 lubricant on the shaft washer

between the armature and the shift lever housing. Other
The starter is a heavy duty, solenoid-operated D.C. than periodic lubrication and keeping cable connections
cranking motor. The unit has an enclosed shift lever and clean and tight, the starter requires no maintenance.
solenoid plunger to protect them from exposure to dirt, The brushes can be inspected by removing the
icing and splash. The commutator end cap can be commutator end cap. However, the starter must be
removed to inspect the brushes (Figure 1). removed and partially disassembled to replace the
brushes.

TROUBLESHOOTING
Ensure that the battery is fully charged then proceed
as follows:
1. Inspect the wiring for damage (Figure 2). Inspect all
connections to the starting motor, solenoid, ignition
switch or multiplexing modules and all ground
connections.
2. Clean and tighten connections as required.
3. Inspect all switches and solenoids to determine
their condition. As required troubleshoot
multiplexing controls.

FIGURE 1. 50MT Starter Motor

OPERATION
The start switch energizes the starter solenoid to
engage the pinion gear and crank the start motor. If the
pinion gear does not mesh with the ring gear, the motor
will not energize to protect both gears from tooth
damage. The pinion gear and motor will stay engaged,
cranking the motor, until the start switch is released and
the return spring disengages the pinion gear.

Starter Protection
The engine ECU has a start enable signal to lock out
the starter once the engine is running. A clutch drive FIGURE 2. Typical Starter Wiring Circuit
between the starter motor and the pinion gear prevents
the motor from reaching excessive speed.
4. If the electrical circuits are functional, the starter
needs repair.
MAINTENANCE
REMOVAL
Under normal operating conditions, no maintenance 1. Turn the main battery disconnect switch off.
is required between engine overhaul periods.
2. Apply the park brake and ensure the engine run
switch and rear start switch are off.
LUBRICATION
Lubrication is provided in the sintered bronze 3. Label and disconnect the electrical wires at the
bushings by an oil saturated wick. Add oil to each wick starter.
by removing an oil reservoir cup which is accessible on 4. Remove the mounting nuts. Ensure that the starter
the outside of the motor. is properly supported.
All bearings, wicks and oil reservoirs should be 5. Pull the starter off the mounting studs and remove it
saturated with an SAE 20 oil. Place a light coat of Delco from the engine compartment.

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 Date March 2003 Page 7C-3

STARTING MOTOR TESTS 6. Compare the starter’s performance to the following

specifications.
Armature Movement
NOTE: A carbon pile is not required unless a battery
1. With the starter removed from the engine, check the
load test will be performed.
armature for freedom of rotation by prying the
pinion with a screwdriver. Tight bearings, a bent
armature shaft, or a loose pole shoe screw will
cause the armature to bind. Test Min. Max. Min. Max.
Voltage Draw Draw RPM RPM
2. If the armature does not turn freely, disassemble the (Amps) (Amps)
motor. If the armature does rotate freely, the motor
should be given a no-load test before disassembly. 20 80 125 5500 8500

The voltage need not be identical to the chart. A

No-Load Test slightly higher voltage will give a slightly higher RPM with
A no-load test will verify normal motor operation or the current drawn remaining the same.
identify specific problems. The problems can be verified If the starter is within specifications, the motor is in
with tests after the motor is disassembled. The no-load good condition. If not, see the following list of possible
test is used to identify open or shorted fields which are problems.
difficult to check when disassembled and to verify
normal operation of a repaired motor before it is
installed. INTERPRETATION OF TEST RESULTS
1. Connect a voltmeter between the motor terminal to Low speed and high current draw:
the ground return terminal (Figure 3). a. Too much friction - tight, dirty, worn bearings, bent
armature shaft or loose pole shoes allowing
armature to drag.
b. Shorted armature - Check further after
Battery disassembly.
24V
-- + c. Grounded armature or fields - Check further after
disassembly.

Failure to operate with high current draw:

a. A direct ground in the terminal or fields.

Failure to operate with no current draw:

a. Open field circuit - This can be checked after
disassembly by inspecting terminal connections
and tracing circuit with a test lamp.
b. Open armature coils - Inspect the commutator for
badly burned bars after disassembly.
FIGURE 3. No-Load Test c. Broken brush springs, worn brushes, high
insulation between the commutator bars or other
causes which would prevent good contact between
2. Connect an ammeter between the solenoid’s the brushes and commutator.
battery terminal and a 24V battery.
Low speed and low current draw:
3. Connect a switch between the solenoid’s battery
a. A high internal resistance due to poor connections,
and switch terminals.
defective leads or a dirty commutator.
4. Connect the starter’s ground terminals to the
battery. High speed and high current draw:
5. Holding a tachometer on the pinion shaft, close the a. A shorted field. If shorted fields are suspected,
switch and record the voltage, current draw and replace the field coil assembly and check the motor
speed of the starter. for improved performance.

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 Date March 2003 Page 7C-4

DISASSEMBLY ARMATURE - (TESTING)

Check the armature for opens, short circuits and
1. Match-mark the solenoid, lever housing, and nose
grounds as follows:
housing so the starter motor can be reassembled in
the same positions. Opens
Opens are usually caused by excessively long
2. Disconnect the field coil leads from the solenoid
cranking periods. The most likely place for an open to
motor terminal and the solenoid ground terminal.
occur is at the commutator riser bars. Inspect the points
3. Remove the brush inspection plugs, and unfasten where the conductors are joined to the commutator bars
the brush lead screws. This will disconnect the field for loose connections. Poor connections cause arcing
leads from the brush holders. and burning of the commutator bars during cranking. If
the bars are not too badly burned, repair by resoldering
4. Remove the commutator end frame from the field the leads in the riser bars (using rosin flux). Turn the
frame. commutator in a lathe to remove the burned material.
5. Separate the nose housing and field frame from the Shorts
lever housing. Short circuits in the armature are located with a
6. Remove the armature and clutch assembly from the growler. Revolve the armature in the growler with a steel
lever housing. strip such as a hacksaw blade held above it. The blade
will vibrate above the area of the armature core where
7. Separate the solenoid from the lever housing. the short circuit is located. Shorts between bars are
sometimes produced by brush dust or copper between
the bars. Eliminate these shorts by cleaning out the slots
Cleaning (Figure 4).
Clean all parts except the drive with mineral spirits
and a soft brush. Wipe the drive with a clean dry cloth.

CAUTION
Do not clean the drive, armature or fields in a
degreasing tank or with degreasing solvents;
the drive lubricants will be removed and the
insulation in the armature and field coils will
be dissolved.

FIGURE 4. Armature Shorting Test

Grounds
Use a 110VAC test lamp and test points to detect
BRUSHES AND HOLDERS grounds in the armature. If the lamp lights when one test
Inspect the brushes for wear. Replace if worn. Make point is placed on the commutator with the other point
sure the brush holders are clean and the brushes do not on the core or shaft, the armature is grounded. Grounds
bind in the holders. The full brush surface should ride on occur because of insulation failure. This is often caused
the commutator. Ensure that the brush springs give firm by starting motor overheating or by brush dust
contact between the brushes and the commutator. accumulation between the commutator bars and the
Replace springs if distorted or discolored. steel commutator ring.

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FIELD COIL TEST SOLENOID TEST

A typical circuit is shown in the wiring diagram of With all other leads disconnected, check the solenoid
Figure 5. Check the field coils for grounds and opens by windings by making the test connections shown in
using a 110 volt test lamp: Figure 6.

HOLD---IN PULL---IN
WINDING WINDING

G S
M BATT

START
SWITCH

BATT.

FIGURE 6. Internal Solenoid Circuit

Hold-In Winding
FIGURE 5. Internal Starter Wiring Make connections to the “S” and ground return
terminals (Figure 7). If needed, use the carbon pile to
decrease the battery voltage to the value specified.
Connect one lead of the 110VAC test lamp to the field Compare the ammeter reading with the hold-in winding
frame and the other lead to the field connector. If the specifications. High current draw indicates a shorted
lamp lights, at least one field coil is grounded. It must be winding, and low current draw indicates excessive
repaired or replaced. This check cannot be made if the resistance.
ground lead cannot be disconnected.

Opens
Connect the test lamp leads to the field coil ends. If
the lamp does not light, the field coils are open.
Remove field coils from the field frame assembly by
using a pole shoe screwdriver. A pole shoe spreader
may also be used to prevent distortion of the field frame.
Careful installation of the field coils is necessary to
prevent shorting or grounding of the field coils as the
pole shoes are tightened into place.
Where the pole shoe has a long lip on one side and a
short lip on the other, assemble the long lip in the
direction of armature rotation so it becomes the trailing
(not leading) edge of the pole shoe. Figure 7. Testing Hold-In Winding

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 Date March 2003 Page 7C-6

Pull-In Winding BUSHING REPLACEMENT

To check the pull-in winding, connect from the 1. Remove the expansion plug from the armature shaft
solenoid switch terminal to the solenoid motor terminal bore.
(Figure 8). Compare the ammeter reading with the
pull-in winding specification. High current draw 2. Remove the expansion plug from the oil reservoir.
indicates a shorted pull-in winding, and low current draw 3. Remove the pipe plug from the oil wick passage.
indicates excessive resistance. 4. Remove the packing land oil wick from the reservoir.
5. Press the old bushing from the end frame.
6. Press the bushing into place.
7. Soak tangent wicks in SAE 20 oil.
8. Insert wick.
9. Dip bearing in SAE 20 oil.
10. Insert bearing.

NOTE: It is not necessary to cross-drill a sintered

bearing with a tangent wick. Because the bearing is
so highly porous, oil from the wick touching the
outside bearing surface will bleed through and
lubricate the shaft.

FIGURE 8. Pull-in Winding Test

SOLENOID TEST SPECIFICATIONS CAUTION

Pull-In Winding Hold-In Winding Do not drill, ream or machine sintered
bearings in any way. These bearings are
Test Current Resist- Test Current Resist- supplied to size. If drilled or reamed, the
Voltage Draw ance Voltage Draw ance
inside diameter will be too large and the
10 20---23 0.44 to 20 6.1-6.8 2.94 to bearing pores will be sealed.
0.5 3.26
ohms ohms

NOTE: To avoid excessive heating, do not energize

The middle bearings are support bearings and
the pull-in winding for more than 10 seconds at a time.
prevent armature deflection during cranking. As
Heating will damage the winding. compared to end frame bearings, the clearance
between middle bearing and shaft is large and the
clearance provides a loose fit when assembled.
Grounds
11. Install a new expansion plug with gasket in the
To check for grounds, move the battery lead from the
armature bore in the end frame.
“M” terminal to a clean metal ground on the solenoid
case. The ammeter should read zero. If not, the hold-in
or pull-in winding is grounded. CLUTCH DRIVE REPAIR
The drive pinion must rotate freely in the overrunning
NOTE: To reduce the voltage to the specified value,
direction and must not slip in the cranking direction. The
connect the carbon pile between the battery and the
Positork Drive clutches are replacement only.
“M” terminal as shown.

Check the magnetic switch in the same manner by ASSEMBLY

connecting across its winding. Assemble by reversing the disassembly procedure.

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 Date March 2003 Page 7C-7

PINION CLEARANCE
To check pinion clearance proceed as follows:
1. Make the connections as shown in Figure 9.

FIGURE 10. Pinion Clearance Measurement

5. Adjust clearance by removing plug and turning
shaft nut.

INSTALLATION
1. Properly supporting the starter, raise it into position
FIGURE 9. Pinion Clearance Test on the studs that fasten it to the engine.
2. Secure the starter with the mounting fasteners and
torque to 140 ft-lbs (190 N.m) torque for all engine
2. Flash a jumper lead from the ground return terminal installations with aluminum housings.
to terminal MTR. The drive will now shift into
3. Connect the electrical wires as previously labeled.
cranking position and remain so until the battery is
disconnected. 4. Set the main battery disconnect switch to “ON.”
5. Start the engine to test its operation.
3. Push the pinion or drive back toward the
commutator end to eliminate slack movement. STARTER LOCKOUT
4. Measure the distance between drive and housing The starter lockout circuit is controlled through the
(Figure 10). DDEC IV.

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SPECIFICATIONS
Starter Motor
Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Delco-Remy MT
Rotation (Drive End) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Clockwise
Pinion Clearance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.327”---.0389”
No-Load Test
Volts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Current Draw (Amps) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80---125 amps
RPM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5500---8500 RPM
Starter Solenoid
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Delco---Remy
Test Specifications
Pull-In-Winding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20---23 Amps at 10 VDC
Hold-In Winding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1---6.8 Amps at 20 VDC

MOTOR COACH INDUSTRIES

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 Date March 2003 Page 7D-1

SECTION 7D

ALARMS AND SIGNALS

CONTENTS OF THIS SECTION

SUBJECT PAGE
Alarm Buzzers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7D-2
Turn Signal Flasher . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7D-2
Horns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7D-2
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7D-3

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 Date March 2003 Page 7D-2

ALARM BUZZERS
The alarm system buzzer is in the instrument panel
and the chime is mounted behind the lower left-hand
panel in the driver’s area, on the dash sub-structure
(Figure 1). They are not adjustable.

FIGURE 2

FIGURE 1

TURN SIGNAL FLASHER

Relay modules (Section 7G) provide this function.
FIGURE 3

HORNS
The coach is equipped with two 24V electric horns
located in the left-hand front service compartment.
(Figure 2).
The electric horns are operated by pressing a switch
panel on the steering wheel.(Figure 3) The air horns are
operated by pressing a button on the end of the turn
signal “smart stick.”.(Figure 4)

The only maintenance that may be required is an

electric current adjustment of the adjusting screws on
the electric horns. On each system, one horn produces a
high note and the other a low note. FIGURE 4

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SPECIFICATIONS
LOW AIR PRESSURE SWITCH
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Texas Instruments
Terminals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SPDT
Maximum operating Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500 psi
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Contacts set to transfer at 95 psi(max) increasing pressure
Contacts reset at 75 psi as pressure decreases
Setting Tolerance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 psi ±5 Increasing
68 psi±5 decreasing

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 Date March 2003 Page 7E-1

SECTION 7E

BATTERIES
CONTENTS OF THIS SECTION

SUBJECT PAGE
Batteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7E-2
Battery Disconnect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7E-2
Battery Box . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7E-2
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7E-2
Cleaning and Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7E-2
Checking Electrolyte and Gravity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7E-3
Battery Charging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7E-3
Causes of Battery Failure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7E-3
Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7E-4
Booster Starting and Charging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7E-5
Auxiliary 12-Volt Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7E-6
Battery Equalizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7E-7
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7E-8

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 Date March 2003 Page 7E-2

BATTERIES NOTE: Keep the battery vent plugs securely in place

during this procedure to prevent soda solution or
BATTERY DISCONNECT water from entering the cells.
The main battery disconnect switch shuts off both
Inspect all grommets and cable hangers to ensure
12/24 volt electrical supply from the batteries, except for
that the battery cables make a proper connection.
the engine ECU, the transmission ECU and the auxiliary
heater. The dual 12/24 volt switch assembly is panel If the battery posts or cable clamps are corroded or
mounted to the left of the batteries. It can be reached by pitted, clean them separately with soda solution and a
opening the electrical compartment access door. To stiff wire brush. Stubborn deposits may require careful
disconnect the batteries, push the switch in (Figure 1). removal with a knife.
After all surfaces are clean and dry, reconnect the
BATTERY BOX cables to the battery posts, observing proper polarity.
The battery box is a high-density polyurethane case Tighten the cable terminals securely onto the battery
that has two corrosion-resistant plastic doors for access posts. Apply a liberal coating of neutral dielectric
to the caps and battery cables. The front of the battery lubricant on the cable terminals and battery posts to
box is open for access when the battery compartment prevent acid deposit build-up.
door is open. The box seals up to the battery Check the electrolyte level in the battery cells at least
compartment door when this door is shut. Holes in the every week or 5,000 miles (8,000 km). The check can be
door exhaust battery fumes to the exterior. Small holes in facilitated by using a mirror and flashlight. After
the floor allow battery and wash fluid to escape. removing the cell vent plugs, hold the mirror over the cell
to be checked and direct the flashlight beam into the
CAUTION mirror to check the electrolyte level. If the electrolyte level
in any cell is low, add sufficient distilled water to bring the
level up to the bottom of the cell vent well.
Keep the contact surface between the ac-
cess door seals and the top of the battery
box clean to ensure that battery fumes do
not escape into the engine compartment.

MAINTENANCE
CLEANING AND INSPECTION

CAUTION
Maintain battery connections as shown on
the decal inside the battery compartment or
damage to electrical equipment will result. FIGURE 1

Check the external condition of the batteries and

battery cables periodically. Keep the top of the battery
CAUTION
clean and the battery bolts tight, but do not overtighten.
Keep cable clamp bolts tight. Use only distilled water in battery cells to
prevent the introduction of impurities in the
If a build-up of acidic residue occurs on the battery
batteries. Do not add any substance to the
surface, the posts, cables or on compartment surfaces, electrolyte except distilled water. Do not
apply a solution of baking soda and water with a brush to overfill the cells, since electrolyte expands
neutralize and remove it. Flush all affected areas with during battery use.
clean water and dry these areas thoroughly.

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 Date March 2003 Page 7E-3

ELECTROLYTE SPECIFIC GRAVITY CHECK

The minimum permissible specific gravity for CAUTION
electrolyte in each battery cell is 1.200. As the following
table shows, electrolyte with this specific gravity will Replace batteries only in matched pairs.
freeze at a temperature of -17_F (-27_C). Use batteries of the required specifications
Before checking any cell’s electrolyte specific gravity, only. Refer to the specifications listed at the
first add distilled water if necessary to bring the level up end of this section.
to the required point. If a substantial amount of distilled
water is added to any cell, charge the battery before the
specific gravity is checked. Refer to the Battery Charging BATTERY CHARGING (OPTIONAL)
procedure below. An on-board battery charger, rated at 42 amps, is
available for charging the battery. It operates
automatically when plugged in to a 110 volt, 15 amp
NOTE: Since specific gravity varies with temperature,
circuit. For operation and specifications, see the battery
use a temperature-correcting hydrometer for the
charger section.
following step.

Check the electrolyte’s specific gravity in each battery CAUTION

cell. No cell should have a specific gravity of less than
1.200. If any cell specific gravity tests below 1.180,
Do not allow electrolyte temperature to ex-
charge the battery according to the instructions below, ceed 125_F (52_C) during charging. If the
and recheck the specific gravity. temperature rises, decrease the charging
voltage.

FREEZING TEMPERATURE
SPECIFIC GRAVITY (DEG) F (DEG) C CAUSES OF BATTERY FAILURE
Besides the breakdown of internal battery
1.100 +18 -8
components, battery failure may be caused by a faulty
1.120 +14 -10 electrical component associated with the coach
1.140 +8 -13 electrical system, or a condition existing within the
electrical system. Such causes include the following:
1.160 +2 -17
a. A defect in the alternator or voltage regulator, or a
1.180 -6 -21 faulty connection (high-resistance or open)
1.200 -17 -27 associated with these components.
1.220 -31 -35 b. A defective starter motor or the excessive use of
accessories over long runs.
1.240 -51 -46
c. Defective electrical accessories which tax the
alternator beyond its capacity to produce charging
If the difference in specific gravity is 0.050 or more current.
from the highest to the lowest cell, for any single battery d. Dirt, electrolyte or acidic deposits on the top
after charging, the battery requires replacement. surfaces of the batteries.

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TESTING BATTERY TEST

Since the primary purpose of the coach batteries is to
RECOMMENDED TESTING EQUIPMENT supply cranking power for the engine, a cold cranking
The following items are recommended to perform the performance battery test is the most meaningful test to
tests of electrical equipment, including batteries: determine the condition of the batteries. It is based on
S One 0-500 amp. clamp-on ammeter to indicate the requirement that a 12V automotive battery be able to
alternator output. maintain 7.2 volts for a 20-second period while turning
S One 10-amp. circuit breaker to be placed in series over an engine at 0_F (-18_C).
with the 15-ammeter when checking the field coil The following procedure will be useful in determining
circuit. the condition of the batteries while they are installed in
S One digital voltmeter. the coach. The batteries are assumed to be in
satisfactory condition if the test readings agree with
S One temperature-corrected battery hydrometer.
those in the table following the procedure.
S Tube of neutral dielectric lubricant.
S Baking soda, jar and small paint brush. NOTE: Test results will not be valid if the starter motor
is defective or if there are high-resistance connections
S Battery terminal and post cleaner. in the starter motor circuit.
S Wire brush.
S Corrosion-resisting felt washers to be placed over the To test the batteries, follow this procedure:
battery posts before cable clamp installation. 1. Place the engine run switch in the engine
compartment in the OFF position to prevent the
HIGH RATE DISCHARGE TEST engine from starting.
2. Place a voltmeter (50-volt scale) across the battery
terminals.
CAUTION 3. Turn the engine over for 15 seconds and record the
lowest voltmeter reading during the 15-second test
DO NOT do this test on a battery suspected period. Refer to the following table for voltage
of being in a discharged state. The specific readings to determine the relative condition of the
gravity must be above 1.230 before conduct- batteries.
ing this test. After slow charging a battery, al-
low the battery to stand 8-10 hours before TEMPERATURE MINIMUM TEST VOLTAGE
conducting this test.
70_ 19.2
60_ 18.8
1. The battery must be installed in the coach. Place the
50_ 18.6
voltmeter range selector to measure 10VDC.
2. Check the voltage drop between the grounded 40_ 18.2
(negative) battery terminal and vehicle frame. With 30_ 17.4
the starting motor turning over, the voltage reading 20_ 16.4
should be less than 0.3 volts. If it is higher, the circuit
has excessive resistance. 10_ 15.8
3. Check the voltage drop between the battery’s 0_ 14.4
positive terminal and the starting motor terminal A defective battery condition is indicated if the lowest
stud while the starting motor is turning over. If the voltage reading during the 15 seconds of engine
reading is more than 10 volts, the resistance is cranking is less than the minimum test voltage for the
excessive. appropriate ambient temperature. The above procedure
4. Check the voltage drop between the starting motor requires batteries to be fully charged and cells to be filled
housing and the coach frame. If it is over 0.2 volts, to capacity with electrolyte of the correct specific gravity.
the resistance is excessive. These subjects are discussed above.

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BOOSTER STARTING & CHARGING CONNECTING BOOSTER CABLES

1. Set the parking brake.
2. Turn the lights, heater and other loads off.
3. Remove the vent caps from both the booster and
the discharged batteries. Lay a cloth over each
WARNING battery’s open vent wells. These two actions help
reduce the possibility of an explosion, which is
always present when connecting a “live” booster
Any procedure other than the following battery to a dead battery.
could result in:
4. Attach one end of one jumper cable to the positive
1. Personal injury caused by electrolyte terminal of the booster battery (identified by a red
squirting out of the battery vents. color “+” or “P” on the battery case, post or clamp),
2. Personal injury or property damage due and the other end of the same cable to the post on
to battery explosion. top of the lower waste tank, below the A/C
3. Damage due to the booster vehicle’s compressor base (Figure 2). A rubber boot covers
charging system or that of the this post during normal coach operation, and must
immobilized vehicle. be removed when attaching booster cable.
NOTE: Do not permit vehicles to touch, because this
could establish a ground connection and counteract
Do not attempt to jump start a vehicle having a frozen the benefits of this procedure.
battery, because the battery may rupture or explode. If a
5. Attach one end of the remaining negative (---) cable
frozen battery is suspected, examine all fill vents of the
to the negative terminal (black color “-” or “N” of the
battery. If ice is visible, do not attempt to start the vehicle
booster battery, and the other end to the ground
with jumper cables while the battery remains frozen.
stud on the top of the air compressor front mounting
Treat both the booster battery and the discharged
rail (Figure 2). Take care that clamps from one cable
battery carefully when using jumper cables. Follow
do not inadvertently touch the clamps on the other
EXACTLY the procedure outlined below, being careful
cable.
not to cause sparks.
DISCONNECTING BOOSTER CABLES
1. Taking care that clamps from one jumper cable do
not touch clamps on the other jumper cable,
disconnect the jumper lead from ground stud on
the vehicle being started.
2. Remove one end of negative (-) jumper cable from
the booster battery.
3. Remove the end of the remaining jumper cable from
the post on the side of the front mounting rail of the
A/C compressor, then remove the other end of the
same cable from the positive terminal of the booster
battery. Secure the rubber boot over the post on the
POSITIVE
NEGATIVE A/C compressor mounting rail.
BOOST POST BOOST POST
4. Remove the cloths from the open vent wells of each
battery. Discard these cloths since they may have
FIGURE 2 corrosive acid on them. Install vent caps on both the
booster and the discharged battery.

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AUXILIARY 12-VOLT POWER

12-VOLT POWER (40-AMP. LIMIT)
There are four 12 volt power supplies in the driver’s
area (Figure 3):
1. Two 12-volt power sources fused at 10 amps.
2. A polarized two-pin outlet, fused at 10 amps.
3. A five-way binding post.

FIGURE 3

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BATTERY EQUALIZER OPERATION

The Equalizer causes the 12 volt current draw to be
taken from both the batteries of the 24 volt system.For
DESCRIPTION
example; if a 10 amp., 12 volt load is presented to the
The coach has a 100-amp. battery equalizer
system, 5 amps would be supplied by battery A and 5
(Figure 4). The battery equalizer circuit is protected by a
amps would be supplied by battery B.
105 amp breaker. This system maintains the voltage
balance and charge acceptance rate of each battery to MAINTENANCE
anywhere from 0.1 to 0.01 volts under a light load and 1. Clean the exterior of the equalizer regularly.
0.5 volts with a full load.
2. Ensure all connections are clean and tight.
With this system, the equalizer system will maintain a
balance between the two batteries. TROUBLESHOOTING
Any time that wire connections are hot, that the studs,
NOTE: When replacing only one of the batteries, nuts, fuse cover or insulation are discolored, that there is
install the new battery in the grounded position (at the low or no output, or that there is an audible noise or tick
rear of the battery compartment). from the converter clean the connections and as
required replace the fuse link.
1. Remove all nuts and metal washers.
2. Clean all stud threads with steel wool, etc.
3. Burnish the face of the jam nuts that contact the
fuse.
4. Refit the washers and jam nuts on the studs.
Tighten and loosen several times to ensure good
electrical contact.
5. Burnish the fuse link side that contacts the jam nut.
6. Reinstall the fuse cover. flat washers, and outside
nuts. Tighten securely.
EQUALIZER
REMOVING THE BATTERIES

WARNING
Batteries weigh approximately 130 lbs (59
kg) each. Take care when lifting and moving
CIRCUIT BREAKER batteries.

To remove the batteries:

1. Remove the battery cables.
2. Loosen the capscrew at the hold-down between the
batteries.
3. Lift and slide the batteries out, using the handles
FIGURE 4
provided at the battery case.

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SPECIFICATIONS
BATTERIES (24-VOLT SYSTEM)
Ampere Hour Capacity at 20 Hour Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
Number of Plates Per Cell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Separators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Plastic
Reserve Capacity @ 25 amp. rate and 81oF (27oC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 450 mins.
Cold Cranking At 0_F (-18_C) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1350 amps
Weight Dry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 lbs. (47 kg)
Weight Wet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146 lbs. (66 kg)
Acid to Fill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.2 Qts. (U.S.)(15.4 liters)
Number of Batteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
SAE Number . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8D
Terminal type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Negative
Grounded Terminal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Tapered SAE
Operating temperatures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ---50oC to +50oC (---58oF to +122oF)
Applicable Standards . . . . . . . . . . . . . . . . . . . . . . . . . . SAE J537, J2185, J1495, BCI Battery Technical Manual

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SECTION 7F

LIGHTS, BULB DATA AND SPECIFICATIONS

CONTENTS OF THIS SECTION

SUBJECT PAGE
Headlight Assemblies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7F-2
Front Turn Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7F-3
Taillight Assemblies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7F-3
Parcel Rack Lights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7F-4
Instrument Panels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . NO TAG

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HEADLIGHT ASSEMBLIES door. Proceed per the curbside instructions.

The headlights are projector style, that provide

increased lighting for night driving. Each headlight unit
has one high beam and one low beam lamp.

OPERATION
A switch on the right-hand dash controls the
headlights. The turn signal lever controls the high beam:
pull the turn signal lever up for flash-to-pass with the
headlamp switch off. With the headlight switch on,
pulling the lever up will toggle between high and low
beams.

MAINTENANCE
Check light operation daily as part of the pre-trip
inspection. (See Operator’s Manual.)
Clean the front lenses with soap and water and a
good glass cleaner whenever they are dirty.
For maximum light output, keep the headlights clean
and maintain the proper voltage. A low battery, loose or
dirty electrical contacts, and poor ground can all
contribute to a decrease in voltage.
Check the wiring and connections regularly and keep
the battery properly charged.

Replacing Curbside Lamps

When a headlamp burns out, install a new lamp:
1. Remove the access panel below the passenger
side dash.
2. Take off the snap plug over the headlight bracket
(Figure 1).
3. Give the lamp holder 1/8 turn counter-clockwise to
remove the lamp.
4. Being careful not to touch the glass, install the new
lamp and reinstall the lamp holder with a 1/8
clockwise turn.

Replacing Roadside Lamps

Access to the road side light is via the left front service FIGURE 1

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Aiming Curbside Headlamps NOTE: Do not, under any circumstances, adjust the
The headlights are factory-aimed and should need no pivot bolt.
adjustment. If an adjustment is needed, due to a
collision or other problem, proceed as follows:
1. Make sure the coach is on perfectly level ground.
2. Remove the panel under the curb-side dash to FRONT TURN SIGNAL
access the headlight.
3. Remove the caps from the plastic housing to access The front turn light bezel is mounted beside the
headlamp bezel. To remove a lamp, remove the same
the adjustment screws and bubble level (Figure 2).
panel as for the headlamp (above) and turn the bulb
assembly 1/4 turn (Figure 3).

FIGURE 2 FIGURE 3
4. Adjust the vertical adjustment screw to center the
bubble in the level.
5. Adjust the horizontal adjustment screw to adjust the TAILLIGHT ASSEMBLIES
left-right aim of the headlight. The locator wheel has The taillight housings are mounted to the rear corners
an arrow that points up to show the factory-set of the coach.
condition. The taillight assemblies (stop, tail, turn and back-up)
Aiming Roadside Headlamps are LED and require no maintenance.
Access to the roadside light is via the left front service The assemblies have three lamps on each side of the
door. Proceed per the curbside instructions, except that coach. One lamp is for back-up warning, one is a
the levelling bubble is on the underside of the unit. stop/taillamp, and the top is a turn indicator.

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PARCEL RACK LIGHTS Florescent Tubes

Access to the light tubes is gained by removing the
Reading Lights lens as follows:
The reading light bulbs are designed for long life and 1. Remove the vinyl snap-in molding by inserting a flat
rarely require replacement. To replace the parcel rack tip screwdriver under the lip of the molding (near the
reading lights (Figure 4): molding joint).
1. Remove the lens with a slot-end screwdriver. 2. Pry the molding from the housing track.
2. Grasp the bulb and pull it directly out. 3. Remove lens to expose the bulbs.
3. Press the new bulb into the socket. 4. To replace the lens, first position the lens in the
housing groove.
5. Then position the molding in the housing track and
push up to snap the lock molding in.

SWITCHES
With the exception of the mirrors, all instrument panel
switches have LED illumination. This means they should
never require service. Should an LED fail, it can be
reached by snapping off the rocker, either by hand or
with a small screwdriver. To replace the mirror switch
bulb, pull out the small drawer to access the bulb.

FIGURE 4

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 Date March 2003 Page 7G-1

SECTION 7G

MULTIPLEX SYSTEM
CONTENTS OF THIS SECTION

SUBJECT PAGE
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7G-2
PDM Footprtint and Pinouts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7G-6
Module Footprint and Pinouts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7G-10
Input Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7G-12
Logic Ladder Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7G-13
Diagnostic Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7G-17

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GENERAL DESCRIPTION

PDM MODULE DESCRIPTION

The PDM is a general purpose high current switch device for 12V or 24V. It is designed to take power in through two
power cables (called bus bars) and distribute this power to pins on the output connector. The PDM is a solid state
device with no electromechanical components. Two stage electronic fusing provides fast short circuit protection and
slower over current protection. It mimics a fuse operation and allows for inrush currents without nuisance tripping. The
solid state design is more robust than electromechanical designs because there are no physical contacts that wear.
The PDM also offers two low current bidirectional outputs that behave like single pole, single throw (SPST) relays.
The PDM has 20 diagnostic LEDs that act as quick visual indicators of module faults such as short circuits or
absence of proper in put signals. Please refer to the overlay drawing in section 6.3 for the location of the diagnostic
LEDs.
The PDM is analog in nature and contains no microprocessors or firmware/software. The enable inputs are
designed to drive the appropriate outputs directly when external signals are applied to the enable inputs. There is no
user programming required. No diagnostics are available through a network such as J1939.

PDM HARDWARE
The PDM can be described as four functional blocks:

High Side Outputs 1-- 6

High Side Outputs 7-- 12
Solid State Relay 1 (SSR1)
Solid State Relay 2 (SSR2)

HIGH SIDE OUTPUTS 1---6

Inputs
High Side Outputs 1---6 are all turned on at the same time by one of two input enables. Enable+ is asserted when it is
switched to battery. Enable--- is asserted when it is switched to ground. The enables are fed into an OR circuit. The
outputs will be turned on when Enable+ OR Enable--- is asserted (Pin 26 OR Pin 25).
Outputs
Outputs 1---6 are six individual High Side Outputs. They act as a switch to battery. When the inputs are asserted,
they connect the voltage on Bus Bar 1 to the output pins 1---6. High side outputs typically drive power to vehicle loads
such as bulbs, motors, solenoids and switch---to--- battery signal inputs on ECMs.
Each output is protected with two stage electronic fusing that provides fast short circuit protection and slower over
current protection. Each output will sustain its rated output of 10A or 20A. If current draw rises above this for
approximately 1 second, the output will turn off. In the event of a short circuit, current rises very rapidly. If the current
rises above 42 amps the output will shut off within 5 milliseconds. To reset an output from a protected state, the enables
must be removed and reapplied.

PIN 1, 13, 24 -
BUS BAR 1: 20 AMP
12/24V PIN 2 - 10 AMP
PIN 3 - 10 AMP
PIN 4 - 10 AMP
26: ENABLE 1 PIN 5 - 10 AMP
PIN 6 - 10 AMP

25: ENABLE 2

FIGURE 1

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LED Diagnostics
Outputs 1---6 have 8 LEDs for diagnostics. These are located on the housing overlay.
PWR LED is lit when power is applied to Bus Bar 1
ON LED is lit when the outputs are enabled
(Enable+, or Enable-)
O/P 1---6 LEDs are lit when power is being delivered to the load. If the ON LED is lit and
one or more of the OUTPUT LEDs are not lit, then an output fault has been detected and the output has been turned off.

INPUTS OUTPUTS

1
BUS BAR 1
2
PWR
3
ON
4

FIGURE 2
HIGH SIDE OUTPUTS 7---12
Inputs
High Side Outputs 7---12 are all turned on at the same time by one of two input enables. Enable+ is asserted when it
is switched to battery. Enable--- is asserted when it is switched to ground. The enables are fed into an OR circuit. The
outputs will be turned on when Enable+ OR Enable--- is asserted (pin 28 OR pin 27).
Outputs
Outputs 7---12 are six individual High Side Outputs. They act as a switch to battery. When the inputs are asserted,
they connect the voltage on Bus Bar 1 to the output pins 7---12.
Each output is protected with two stage electronic fusing that provides fast short circuit protection and slower over
current protection. Each output will sustain its rated output of 10A or 20A. If current draw rises above this for
approximately 1 second, the output will turn off. In the event of a short circuit, current rises very rapidly. If the current
rises above 42 amps, the output will shut off within 5 milliseconds. To reset an output from a protected state, the
enables must be removed and reapplied.

BUS BAR 2: PIN 7 - 10 AMP

12/24V
PIN 8 - 10 AMP
PIN 9 - 10 AMP
PIN 10 - 10 AMP
28: ENABLE 1 PIN 11 - 10 AMP
PIN 12, 23, 35
20 AMP
27: ENABLE 2

FIGURE 3
LED Diagnostics
Outputs 7---12 have 8 LEDs for diagnostics. These are located on the housing overlay.
PWR is lit when power is applied to Bus Bar 2
ON is lit when the outputs are enabled.

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(Enable+, or Enable-)
O/P 7---12 are lit when power is being delivered to the load. If the ON LED is lit and one or more of the OUTPUT LEDs
are not lit, then an output fault has been detected and the output has been turned off.

INPUTS OUTPUTS

7
BUS BAR 2
8
PWR
9
ON
10

11

12

FIGURE 4
SOLID-STATE RELAY 1 (SSR1)
Inputs
Enables for SSR1 operate like the connections to a SPST relay coil The Enable+ input (pin 29) must be connected to
battery and the Enable--- input (pin 18) must be connected to a ground to energize the ”coil” and close the ”contacts”
(pin 31 and 32). Either the Enable+ or the Enable--- can be switched in and out to turn the solid state relay ON or OFF.
Outputs
The SSR1 outputs behave in the same manner as a pair of SPST relay contacts. They are not a switch---to---ground
or a switch---to---battery. The SSR1 outputs are bidirectional. They allow current to flow in either direction through the
circuit. The SSR1 output can be used to switch high side, low side, or low ---level signals.
When the output of SSR1 is enabled (Enable+ switched to battery AND Enable--- switched to ground) the contacts
will close and allow current to flow between pins 31 and 32. The SSR1 output has a current sense circuit that monitors
the current and disconnects the relay when current exceeds 6 amps in either direction.
SSR1 has short circuit and over current protection. Short circuit protection occurs at approximately 20A and will
cause the faulted output to turn off in less than 5 milliseconds. Over current protection occurs at 6A with a turn off time
of approximately 1 second. To reset an output from a protected state, one of the enables must be removed and
reapplied.

31

29 ENABLE+
SSR 1

32
18 ENALBE-

FIGURE 5
LED Diagnostics
SSR1 has 2 LEDs for diagnostics. These are located on the housing overlay.
SSR1 is lit when Enable+ is HI and Enable--- is LO
The coil is energized; the contacts should be closed.
O/P 13 is lit whenever the SSR1 LED is on (contacts closed).If it is not, then an output fault has been detected.

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INPUTS OUTPUTS

SSR1 13

SSR2 14

FIGURE 6
SOLID-STATE RELAY 2 (SSR2)
Inputs
Enables for SSR2 operate like the connections to a SPST relay coil The Enable+ input (pin 30) must be connected to
battery and the SSR1 Enable--- input (pin 19) must be connected to a ground to energize the ”coil” and close the
”contacts” (pin 33 and 34). Either the Enable+ or the Enable--- can be switched in and out to turn the solid state relay
ON or OFF.
Outputs
The SSR2 outputs behave in the same manner as a pair of SPST relay contacts. They are not a switch---to---ground
or a switch---to---battery. The SSR2 outputs are bidirectional. They allow current to flow in either direction through the
circuit. The SSR2 output can be used to switch high side, low side, or low ---level signals.
When the output of SSR2 is enabled (Enable+ switched to battery AND Enable--- switched to ground) the contacts
will close and allow current to flow between pins 33 and 34. The SSR2 output has a current sense circuit that monitors
the current and disconnects the relay when current exceeds 6 amps in either direction.
SSR2 has short circuit and over current protection. Short circuit protection occurs at approximately 20A and will
cause the faulted output to turn off in less than 5 milliseconds. Over current protection occurs at 6A with a turn off time
of approximately 1 second. To reset an output from a protected state, one of the enables must be removed and
reapplied.

33

30 ENABLE+
SSR 2

34
19 ENABLE-

FIGURE 7
Led Diagnostics
SSR2 has 2 LEDs for diagnostics. These are located on the housing overlay.
SSR2 is lit when Enable+ is HI and Enable--- is LO
The coil is energized; the contacts should be closed.
O/p 14 is lit whenever the SSR1 LED is on (contacts closed).If it is not, then an output fault has been detected.

INPUTS OUTPUTS

SSR1 13

SSR2 14

FIGURE 8
Summary & Notes
The following table summarizes the inputs and outputs available on the PDM.

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PIN # INPUT NAME INPUT FUNCTION O/P AFFECTED PIN #

26 Enable O/P 1-6 Turns on O/P 1-6 1-6 1-6, 13, 24
when switched to
battery
25 /Enable O/P 1-6 Turns on O/P 1-6 1-6 1-6, 13, 24
when switched to
ground
28 Enalbe O/P 7-12 Yurns on O/P 7-12 7-12 7-12, 23, 35
when switched to
battery
27 /Enable O/P 7-12 Turns on O/p 7-12 7-12 7-12, 23, 35
when switched to
ground
29 SSR1 Eanble+ Turns on SSR1 when SSR1 31, 32
switched to battery
AND SSR1 Eanble-
is switched to
ground
18 SSR1 Enable- Turns on SSR1 when SSR1 31, 32
switched to battery
AND SSR1 Enable+
is switched to
ground
30 SSR2 Enable+ Turns on SSR2 when SSR2 33, 34
switched to battery
AND SSR2 Enable-
is switched to
ground
19 SSR2 Enable- Turns on SSR2 when SSR2 33, 34
switched to battery
AND SSR2 Enable+
is switched to
ground

PDM FOOTPRINT AND PINOUTS

Connectors
35 pin PDM Connector: AMPSEAL P/N 1---776163---1
Mating Connector: . . . AMPSEAL P/N 776164---1
Mating Terminals: . . . . AMPSEAL P/N 770854---3

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1 12
13 23 1 2
24 35

FIGURE 9

PIN # PIN FUNCTION OUTPUT BUS BAR

1 Output 1A 1
2 Output 2 1
3 Output 3 1
4 Output 4 1
5 Output 5 1
6 Output 6 1
7 Output 7 2
8 Output 8 2
9 Output 9 2
10 Output 10 2
11 Output 11 2
12 Output 12A 2
13 Output 1B 1
14 Ground N/A
15 Ground N/A
16 Ground N/A
17 Ground N/A
18 SSR1 Enable- N/A
19 SSR2 Enable- N/A
20 Reserved CAN Shld N/A
21 Reserved CAN+ N/A
22 Reserved CAN- N/A
23 Output 12B 2
24 Output 1C 1

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25 /Enable Outputs 1-6 N/A

26 Enable Ouputs 1-6 N/A
27 /Enable Outputs 7-12 N/A
28 Enable Outputs 7-12 N/A
29 SSR1 Enable+ N/A
30 SSR2 Enable+ N/A
31 SSR1 Contact 1 N/A
32 SSR1 Contact 2 N/A
33 SSR2 Contact 1 N/A
34 SSR2 Contact 2 N/A
35 Output 12C 2
2 Pin PDM Connector: ITT CANON P/N 121583-0027
Mating Connector: . . . 121583-0025
Mating Terminals (AWG 6): 430-8645-002 (AWG 6)
Mating Terminals (AWG 8): 430-8645-003 (AWG 8)
Wire Seals (AWG 6): . . 908-8672-007
Wire Seals (AWG 8): . . 980-8672-009
Hexagonal Nut: . . . . . . 980-8672-000

PIN # PIN FUNCTION

1 Bus bar for outputs 1 to 9
2 Bus bar for oututs 10 to 18
Connector part numbers were valid when this manual was created. Please check manufacturer website for
updates.

SOLID-STATE MULTILEX MODULE (SMM) DESCRIPTION

The SMM is a general purpose multiplexed input/output controller which is designed to allow several digital and
analog inputs to control several solid---state switch outputs according to a logic table or vehicle configuration table. All
input and output state information for the SMM is communicated on a Controller Area Network (CAN) communication
bus which allows one modules inputs to control another Modules outputs and vice versa.

SMM HARDWARE
This section will discuss the various features of the SMM hardware including a description of inputs, outputs,
communications, addressing and diagnostic LEDs.
Inputs
There are two types of inputs on each SMM: digital inputs and analog inputs. Digital inputs read signals that are
either high or low in value (that is, battery voltage or ground), analog in puts read signals that are a voltage value
between 0 volts and 32 volts. Digital inputs are typically connected to vehicle signals that have two states, these
include rocker switches, toggle switches or on/off signals from other vehicle electronic control modules (ECMs).
Analog inputs can be connected to vehicle signals that have a wide range of values between ground and 32 volts, these
include air pressure sensors, fuel level sensors, battery voltages.
The following table shows a list of inputs available on each SMM.

Input Number Input Type Power Save Control

Digital 1 to 5 Switch to ground Yes

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Digital 6 to 10 Programmable: switch to ground or No

switch to battery
Digital 11 to 28 Switch to ground No
Analog 1 0V to 32V No
Analog 2 0V to 32V No
Analog 3 0V to 32V No
Vbat Analog Internally connected to SMM power No
input
Digital inputs 1 to 5 and 11 to 28 can be connected to any signals that are considered active when they are at ground
potential. Digital inputs 6 to 10 can be connected to any signals that are considered active when they are at ground
potential or at battery potential. These inputs are programmed as either switch to battery or switch to ground by the
user depending on which type of signal they are connected to.
Furthermore, digital inputs 1 to 5 also control SMM power save mode. If any of these five inputs are active (ground
potential) then the SMM will power up and begin normal operation; if all of these five inputs are inactive (floating or at
battery potential) then the SMM will power down to Power Save Mode. When the SMM is in power save mode, all power
is disconnected from the microprocessor and logic circuits inside the unit. This allows for a power save mode, which
puts the least amount of drain on the vehicle battery.
SMM Outputs
There are two types of outputs on each SMM, these are high side outputs and bidirectional outputs. The high side
outputs switch battery voltage to output pins, the bidirectional outputs act like single pole single throw relays in that
when they are active they connect two points together. High side outputs are typically used to drive power to vehicle
loads such as bulbs, motors, solenoids and switch to battery signal inputs on other ECMs. Bidirectional outputs are
typically used to connect ground to vehicle loads such as bulbs, motors, solenoids and switch to ground signal inputs
on other ECMs. This typical bidirectional use is called a low side driver, but the bidirectional switches are not limited to
this function, they can be arranged as high side, low side or simply a method of connecting two points together. They
do not require a voltage or a ground on either of their pins to operate (unlike the high side drivers).
Half of the high side outputs are connected to bus bar 1 and the other half are connected to bus bar 2. Each SMM
has two external power pins, one connects to bus bar 1 and the other connects to bus bar 2. This allows a single SMM
to switch either 12V, 24V or both.
The following table shows a list of outputs available on each SMM.

Output Number Output Type Max Continuous Connected to Bus Allowable Load
Current Bar (1/2) Type
1 to 9 High Side 6A Bus Bar 1 Resistive, Bulb, In-
ductive, Motor
10 to 18 High Side 6A Bus Bar 2 Resistive, Bulb, In-
ductive, Motor
19 to 20 Bi-directional 4A N/A Resistive, Bulb, In-
ductive, Motor
Outputs 1 to 18 have a maximum continuous current rating of 6 amps which means that a load of approximately 2.3
ohms can be connected to each output if each output is supplying 14V (4.6 ohms if each output is supplying 28V).
Outputs 19 and 20 are the two bi-directional outputs supplied with the SMM, these have a maximum continuous current
rating of 4 amps which means that a load of approximately 3.5 ohms can be connected to each output if each output is
supplying 14V (7 ohms at 28V).
Outputs 1 to 16 can be Pulse Width Modulated (PWM) which allows the output to send out a 100Hz square wave with
an On to Off duty cycle ratio of 0% to 100%.
All outputs are protected against short circuits, over currents and reverse battery. High side outputs can handle
inrush currents of approximately 42 A for a period of one second, inrush currents of a higher value must drop below the
42 A point within approximately 0.5 ms.

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Short circuit protection turns the corresponding output to the off state, which removes power from the faulted
circuit. Outputs that are in short circuit protection mode will attempt to re---energize the circuit after a 5 second delay, if
the fault is still present the output will turn off again and continue the re---energize cycle until the fault is removed.
Over current protection turns the corresponding output to the off state if an output maintains a current value greater
than 10A for a period of 1 second. Outputs which are in over current protection mode will attempt to re---energize the
circuit after a 5 second delay, if the fault is still present, the output will turn off again and continue the re---energize cycle
until the fault is removed.
Reverse Battery: High side outputs turn on if they sense a reverse battery on the vehicles electrical system. Short
circuit and over current protection is not operational in a reverse battery situation. Bidirectional outputs turn off in a
reverse battery situation and block reverse voltages up to 100V.
Inrush: An inrush, which peaks greater than 42 A and which lasts longer than 0.5 ms will cause the output to enter a
short circuit shotdown mode. No damage will result from inrush current waveforms of this type.
SMM Communications
The SMM has one communication port for use in a multiplex system environment. This communication port is a
Controller Area Network (CAN) type. CAN is a high---speed serial communication network which allows up to 32 nodes
or CAN based ECMs to be connected at any given time. The SMM CAN conforms to the SAE J1939 standards which
makes it an industry standard device that can be used with other CAN J1939 based equipment without conflict. The
SMM CAN operates at a bit rate of 250 kbps (kilo bits per second) which is more than 26 times faster than the industry
standard SAE J1708 communication bus.
The SMM CAN is the multiplex system backbone. It is the communication cable through which all system inputs and
outputs are multiplexed. Each SMM has a CAN port which when connected together in a two or more module system,
creates a CAN communication bus.
SMM Addressing
Each SMM is exactly the same as all other SMMs in a multiplex system. That is, each SMM has the exact same
hardware configuration (28 digital inputs, 3 analog inputs, 1 CAN port, 18 high side outputs and 2 bidirectional outputs)
and each SMM is programmed with the exact same firmware configuration. Since each SMM is exactly the same, a
method of telling which SMM is to perform which task is required. This is accomplished through addressing. The
addressing is done in the harness.
As stated above, the firmware in each module is exactly the same, this means that each module contains the full
vehicle configuration ladder logic. Each SMM then selects which section of the ladder logic to run depending on the
physical wire harness address. This feature allows SMMs to be interchanged without affecting the vehicle operation,
this can be done without the need to reprogram or set dip switches, simply pop, swap and go! The reason you may
want to swap one module with another is for diagnostics, which is discussed further in the SMM Trouble Shooting
Guide.
SMM Diagnostic LEDs
The SMM has two main diagnostic features, one is driven on the CAN communication bus and requires Vansco
SMM software to operate. The second is diagnostic LEDs located on the front of each SMM. The latter will be
discussed in this section.
Each SMM has 28 digital inputs, 20 outputs and a CAN port. Each SMM also has 28 LEDs representing active digital
inputs, 20 LEDs representing active outputs, one LED representing CAN activity and one representing overall module
power/health.
The 28 input LEDs have two states, ON/OFF. If an input LED is ON, the corresponding input that the LED represents
is Active. If an input LED is OFF, the corresponding input that the LED represents is Inactive.
The 20 output LEDs have three states, ON/OFF/FLASHING. If an output LED is ON, the corresponding output that
the LED represents is Active. If an output LED if OFF, the corresponding output that the LED represents is Inactive. If an
output LED is FLASHING, the corresponding output that the LED represents is Faulted. There are four types of faults
that will cause output LEDs to flash, these are short circuit, over current, back drive or if not power is detected at the
output pin.
A short circuit fault occurs when the circuit that a SMM output is driving shorts to ground. An over current fault occurs
when the circuit that a SMM output is driving is drawing excessive current. A back drive fault occurs when the circuit

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that a SMM output is driving is shorted to battery voltage. A no power detected fault occurs if an output circuit is
physically damaged or there is not power on the output bus bars. Note that a back drive fault is detected when an
output is in the off state and the short circuit/over current/no power faults are detected when the output is in the on
state.
The power LED has three states, ON/OFF/FLASHING. If the power LED is OFF, the module is in either power save
mode or the vehicle power has been completely disconnected. If the LED is ON, the module is powered up and is
operating normally. If the LED is FLASHING, the module is powered up, but it currently has no vehicle configuration
loaded into it or there is an internal SMM fault.
The diagnostic LEDs are designed to ease vehicle debugging. Each LED represents an input or output, and as
such, each LED is essentially a circuit continuity tester. For more information on diagnostic techniques using the SMM
LEDs and the SMM diagnostic software, please refer to the SMM Trouble Shooting Guide.
Plug and Play Automatic Module Programming
The SMM has a very powerful Plug and Play feature, which allows a single module to be replaced in a vehicle system
with a SMM that contains a different vehicle configuration or no vehicle configuration at all without the need for
reprogramming equipment. Upon every system power up each SMM communicates its firmware and ladder logic
revision on the CAN. If one module mismatches the majority, that one module automatically downloads the firmware
and ladder logic from another SMM in the system. Once this process completes, all modules are put online and
continue to operate as though a module was never changed.
This feature is particularly useful for in field module changes in the unlikely event that a module in a system fails to
operate properly.
CAN Diagnostics
The SMM is capable of logging errors in non---volatile memory, which can later be retrieved for analysis by service
personnel. Items that are logged include output faults, CAN failures and user selectable event counters and timers.
Output faults and CAN failures are automatically logged by the SMM, this function is not user customizable. Output
faults and CAN failures are logged once per type of event. For example, if output 1 faults due to a short circuit, this event
is logged. If the short occurs again on output 1, before service personnel have cleared this log, the second event will
not be logged. If however, another output shorts ( or faults in some way) this will be logged as a separate event.
User selectable event counters and timers are user customizable features for the SMMs which are set in the SMM
software when creating ladder logic. Event counters allow the user to set up a log for a specific event (such as door
solenoid activation) and count whenever this event goes true. In a similar manner, event timers count time duration of
an event being active in increments of seconds. These log types are set up in the ladder logic for the vehicle in the same
way that outputs are defined in the ladder logic. See the SMM Software User Guide for more information on this. Each
SMM has a maximum of 8 counter or timer logs available. Each counter has a maximum of 65536 counts available and
each timer has a maximum of 665536 seconds ( 18 hours). If the maximum count or time is reached in the event
counters or timers, they will retain this maximum value and will not clear the log or start again from zero.
Using the Vansco SMM software application, fault logs event counts and event timers can be retrieved and cleared.
This application also allows real time viewing of system logic operations and allows inputs and outputs to be forced to
active/inactive states regardless of what the input/output is supposed to be doing (this is useful for vehicle logic
debugging, but should be used with caution).

MODULE FOOTPRINT AND PINOUTS

35 PIN SMM Connector:AMP P/N 1-776163-1
Mating Connector: . . . AMP P/N 776164-1
Mating Terminals: . . . . AMP P/N 770854-3

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1 12
13 23 1 2
24 35 3

FIGURE 10

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PIN # PIN FUNCTION OUTPUT BUS BAR

1 Output 6 1
2 Output 5 1
3 Output 4 1
4 Output 3 1
5 Output 2 1
6 Output 1 1
7 Output 10 2
8 Output 11 2
9 Output 12 2
10 Output 13 2
11 Output 14 2
12 Output 15 2
13 Output 7 1
14 Reserved N/A
15 Reserved N/A
16 Reserved N/A
17 Reserved N/A
18 Reserved N/A
19 Reserved N/A
20 Reserved N/A
21 Reserved N/A
22 Reserved N/A
23 Output 16 2
24 Output 8 1
25 Output 9 1
26 Ouput 19 A N/A
27 Output 19 B N/A
28 Reserved N/A
29 Reserved N/A
30 Reserved N/A
31 Reserved N/A
32 Output 20 B N/A
33 Output 20 A N/A

PIN # PIN FUNCTION OUTPUT BUS BAR

34 Output 18 2
35 Output 17 2
3 PIN SMM Connector: AMP P/N 21389-2
Mating Connector: . . . AMP P/N 213905-1

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Mating Terminals: . . . . AMP P/N 213841-3

PIN # PIN FUNCTION

1 Bus bar for outputs 1 to 9
2 Bus bar for outputs 10 to 18
3 Reserved

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INPUT CONNECTORS:
35 PIN SMM Connector: AMP P/N 1-776163-1
Mating Connector: . . . AMP P/N 776164--1
Mating Terminals: . . . . AMP P/N 770854-3

1 12 1 8
13 23 9 15
24 35 16 23

FIGURE 11

PIN# PIN FUNCTION

1 Input 1
2 Input 2
3 Input 3
4 Input 4
5 Input 5
6 Input 6
7 Input 7
8 Input 8
9 Input 9
10 Input 10
11 Input 11
12 Input 12
13 Address 1
14 Address 2
15 Address 3
16 Address 4
17 Address 5
18 Analog Input 1

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19 Analog Input 2
20 Reserved
21 Reserved
22 Reserved
23 Reserved
24 +V batt
25 +V batt
26 +V batt
27 GND
28 GND
29 GND
30 GND
31 CAN Shield
32 CAN High
33 CAN Low
34 Reserved
35 Reserved
23 PIN SMM Connector: AMP P/N 1-776087-1
Mating Connector: . . . AMP P/N 770680-1
Mating Terminals: . . . . AMP P/N 770854-3

PIN# PIN FUNCTION

1 Input 13
2 Input 14
3 Input 15
4 Input 16
5 Input 17
6 Input 18
7 Input 19
8 Input 20
9 Input 21
10 Input 22
11 Input 23
12 Input 24
13 Input 25
14 Input 26
15 Input 27
16 Input 28
17 Analog Input 3
18 Reserved

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19 Reserved
20 Reserved
21 Reserved
22 Reserved
23 Reserved

LADDER LOGIC DEFINITION

Ladder logic is a graphical view of standard Boolean logic (AND, OR NOT, etc). It was developed to provide a simple
method of writing and reading complex logic. Ladder logic uses geometric symbols to represent certain aspects of the
system being programmed, for example module inputs would be represented by a symbol and module outputs would
be represented by a symbol. The placement of these symbols and the way they are interconnected creates Boolean
operations. Ladder logic is so named because the logic is drawn in ”rungs” where one rung represents the logic to
activate/deactivate a specific output in the system. Each symbol has several fields associated with it that the user can
alter; these fields define certain required aspects of a symbol. A list of symbols available in the SMM software is shown
below:
Digital Input Symbol

lx-y

Digital.Input.Label

FIGURE 12
This symbol represents digital inputs into SMM input circuits. There are three user changeable fields associated
with this symbol: Name, Label and State. The State field can be either Active High or Low.
Analog Input Symbol

Ax-y

32.0

AnalogInput.Label

FIGURE 13
This symbol represents analog inputs into the SMM Analog input circuits.
There are four user changeable fields associated with this symbol: Name, Label, Threshold and State.

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Output Symbol

Ox-y

Output Label

FIGURE 14
This symbol represents an output state used in a Ladder Logic Rung.There are five user changeable fields
associated with this symbol: Name, Label, Description, State, and Soft Start.
Telltale Symbol

Tx-y

Telltale Label
FIGURE 15
This symbol represents a special type of output, which sends J1939 messages to telltale clusters for turning on/off
dash telltale lights.There are four user changeable fields associated with this symbol: Name, Label, State and
Description.
Flag Symbol

Fx-y

Flag Label

FIGURE 16
This symbol represents a logical output. This output doesnt physically turn a SMM output on/off, it sets a memory
location to true or false. This memory location, or flag, can then be used as an input condition on other rungs in any
SMM. Typically used to simplify ladder logic drawings for repetitive logic.There are four user changeable fields
associated with this symbol: Name, Label, Description and State.

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J1939 Transmit Message Symbol

Sx-y

J1939 Message
FIGURE 17
This symbol represents a message transmission output on the J1939 network. This allows a SMM to send specific
J1939 messages. This is a terminator symbol for a Ladder Logic Rung.There are four user changeable fields
associated with this symbol: Name, Label, J1939 Data and Description.
Timer Symbol

Cx-y
A B
A 00:00:00.000
B 00:00:00.000

Timer Label
FIGURE 18
This symbol represents a timer in a Ladder Logic Rung. This symbol is used to create delay on make, delay on
break, one shot or periodic timing operations. The timer type and time values are displayed within the symbol
box.There are four user changeable fields associated with this symbol: Label, Type, Time A and Time B.
Mathematical Symbol

A + B

A 0
B 0

FIGURE 19
This symbol represents a mathematical calculation or storage operation on a specified source. Valid sources
include analog inputs, values from J1939 message inputs, direct value, etc. Operation and source text appears inside
the symbol box. Valid operations include: Add, Subtract, Multiply, Divide, Greater than, Greater than or Equal, Less
than, Less than or Equal, and Equal.There are three user changeable fields associated with this symbol: Operation,
Source A and Source B. Valid numbers can have up to one decimal place.

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Pulse Width Modulation Symbol

FIGURE 20
This symbol represents a pulse width modulation duty cycle percentage. This box can be placed anywhere in a
ladder logic rung and will cause the output of that rung to pulse width modulate at 100Hz and the duty cycled entered in
the symbols field.
Log Symbol

Lx-y

L
C
Log Label

FIGURE 21
This symbol represents an internal SMM log, which can be set up as either a count log or a duration log. The count
log will increment by one every time the ladder logic run its used in goes true. The duration log will increment by one
every second as long as the ladder logic rung its used in stays true. Count and duration logs maintain their values even
after power is turned off. The user must clear these logs in order to reset them to zero.
The field in the symbols above are required to give the SMM system more information on what the symbol is. A list of all
fields and their functions is shown below.
NAME:
The NAME field tells the SMM system what SMM address and what input or output numbers the symbol represents.
For example, Ix---y is the field for I (Input) #y on SMM address x. The same scheme is used for output and telltale
symbols, for example Ox---y is the name field for O (Output) #y on SMM address x and Tx---y is the name field for T
(Telltale) #y on Telltale Module x. The Flag symbols can be used by all SMMs in a system and therefore dont originate
from a specific SMM address, therefore the NAME field for Flag symbol is simply a number. For example Fy is the name
field for F (Flag) #y. The NAME field for J1939 receive and transmit symbols represents a specific SPN#, for example
SPNx---y is the name field for J1939 SPN (Suspect Parameter Number) y on SMM address x. There is no name field for
timers or mathematical operation.
LABELS:
The LABEL field provides the user with a field for custom labels on the symbol (Ex. ”Park Brake SW” for the input that
receives the park brake sensor). The LABEL field is standard text and can contain any description required by the user.
The LABEL field is the same for all symbols above.
STATE:
The STATE field provides the user with two options, ACTIVE and INACTIVE. When ACTIVE is selected the symbol
appears as it does in the pictures above, when INACTIVE is selected, the symbol appears with a diagonal line through

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it. The STATE field provides the user with a Boolean NOT function. For example, if a Digital Inputs STATE field is set to
INACTIVE the Digital Input becomes TRUE when the physical value of the input is inactive.
DESCRIPTION:
The DESCRIPTION is a text field and is intended to be a rung descriptor.
PWM DUTY CYCLE:
The PWM DUTY CYCLE field is used to specify the PWM value for a SMM output. PWM can be done from 0% to 100%
in 1% increments. The frequency of PWM operation is 100Hz. A setting of 100% in this field is the default for output
symbols and sets the output on constantly.
FLASH:
The FLASH field is specific to Telltale Outputs. This field has two choices, ACTIVE or INACTIVE. When ACTIVE the
telltale output will flash at 50% duty cycle at a TBD frequency.
THRESHOLD:
The THRESHOLD field is available on Analog Inputs and J1939 Receive Messages. The THRESHOLD value is set
such that if the Analog Input or J1939 Message Data Value is greater than the THRESHOLD, that symbol becomes
TRUE in the logic. Note that for analog inputs a STATE field is available as well which reverses the logic of the
THRESHOLD value.
J1939 MESSAGE:
The J1939 MESSAGE field is specific to the J1939 Transmit Output symbol and contains the full J1939 message to be
transmitted.
TYPE:
The TYPE field is specific to the Timer Symbol and can be set to DELAY ON MAKE, DELAY ON BREAK, ONE SHOT,
PERIODIC.
ON TIME
The ON TIME field is specific to the Timer Symbol and sets the length of time (in milliseconds) that the timer is to stay
on for. The ON TIME field must be set for all types selected.
OFF TIME:
The OFF TIME field is specific to the Timer Symbol and sets the length of time (in milliseconds) that the timer is to stay
off for. This field is only used in conjunction with the PERIODIC TYPE field and the ON TIME field. The frequency and
duty cycle are defined by the ON TIME and OFF TIME of the symbol.
OPERATION:
The OPERATION field is specific to the Math Symbol. This field selects the type of mathematical operation that is to
be done on the two SOURCE fields. Valid selections for this field are ADD, SUBTRACT, MULTIPLY, DIVIDE, MOVE.
SOURCE A:
The SOURCE A field is specific to the Math Symbol. In order to do a mathematical operation (such as add, subtract,
multiply or divide) two sources are required. SOURCE A defines what the first source for the operation is. Valid sources
are Analog Inputs, J1850 Message Data or direct values (or numbers). Source A is also the receiving end of the result of
the operation.
SOURCE B:
The SOURCE B field is specific to the Math Symbol. This defines the second source that is to mathematically
calculate with SOURCE A. This field is required for all mathematical functions.

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DIAGNOSTIC TOOL

Diagnostics X

Inputs Outputs Telltales Flags Timers

Module

V1 N... Fo... State R...

V2 I1-1 NO ACTIVE ON
V3 NO INACTIVE OFF
I1-2
V4
I1-3 NO INACTIVE OFF
V5 INACTIVE OFF
I1-4 YES
V6 INACTIVE OFF
I1-5 NO
INACTIVE OFF
I1-8 NO INACTIVE OFF
I1-9 NO INACTIVE OFF
I1-11 NO INACTIVE OFF
I1-12 NO INACTIVE OFF

FIGURE 22

Tool Description
The diagnostic tool provides the user with a real time view of the SMM system while it is operating. The tool itself
displays the vehicle Ladder Logic in a screen very similar to the drawing window, except editing and drawing is not
allowed.
The ladder logic displayed has color---coding depending on the state of inputs and outputs and whether a specific
SMM is powered or not. For example, ladder logic symbols are colored GREEN if the input or output they represent is
active in the system; otherwise the symbols are colored RED. If a SMM is not powered up, the logic symbols are left
uncolored to represent an unknown state.
In addition to viewing, symbols can be forced to ACTIVE or INACTIVE states. That is, a symbol representing SMM 1
input 1 could be forced to ACTIVE state even if the input itself is inactive on the vehicle. The forced state overrides the
actual state and allows the user to create certain conditions in the system to aid in logic and vehicle debugging.
Symbols that are forced ACTIVE are colored green with a dark green box outline around the symbol, those forced
inactive are colored red with a dark red box outline around the symbol. A Sub Window gives a quick view of the current
states of all the symbols in the ladder logic.

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Tool Operation
The diagnostic tool has very simple operation. Symbols within the diagnostic window can be right clicked to bring
up a pop up window of available operations that can be made. Operations include forcing the Symbol State ACTIVE or
INACTIVE, removing a force; all force reset (panic button), and show I/O forcing. The ”panic button” or all force reset
will switch all symbols that were forced back to the value current on the vehicle. Show I/O forcing displays the sub
window of all symbols and their current states.
The description above gives the basic idea behind the diagnostic tool operation, note that the tool is not yet
completed so the information given in this document is subject to change.

DOWNLOAD AND UPLOAD TOOLS

Tool Description
The Download and Upload tools provide the user with a means of downloading new updated Application Firmware,
and the SMM ladder logic. The Download and Upload tools also provide the user with a means of uploading the SMM
ladder logic from the SMMs themselves. The tool itself displays a progress bar and allows the user to select the file for
downloading.
Tool Operation
The Download and Upload tools have very simple operation. For downloading simply choose the file for
downloading by clicking the browse button and then click ”begin” to start the downloading process. For uploading
simply click ”begin” to start the uploading process. When prompted, save the uploaded file under the file name
desired.

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SRM 3
VMM SOFTWARE ADDRESS 5
(REAR DRIVER’S SIDE PARCEL RACK)

J1939 SRM
COMMUNICATION
HARNESSING

PDM 2
(FRONT DRIVER’S
SIDE PARCEL RACK)

PGM
(LEFT OF STEERING
COLUMN)

SRM 1
VMM SOFTWARE ADDRESS 2
(UPPER FRONT J-BOX)

SRM 2
VMM SOFTWARE ADDRESS 3
(LOWER FRONT J-BOX)

PDM 1
(L.H. SERVICE
COMPARTMENT)

ACRONYMS
PGM -- POCKET GATWAY MODULE
PDM -- POWER DISTRIBUTION MODULE
SRM -- SOLID-STATE RELAY MODULE

FIGURE 23. SRM Physical Locations & Software Addresses

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MODULE FUNCTION
Input/Output LED Checklist
Each SRM has an “Output” LED panel numbered 1 to 20 and an “Input” LED panel numbered 1 to 28. The numbers
divided by a slash (/) in the “Input LED” and “Ign Sw enable” columns identify the module (SRM) physical address or
location on the coach and the “Input” LED number. As an example: 1/16 means module (SRM) 1 and input LED 16.
NOTE: The software program “address” is different than the actual “physical address” location of the module (SRM).
As an example: SRM (module)1 is software address 2. SRM 2 is software address 3 and SRM 3 is software address 5.
See Figure 23 for SRM locations on the coach.Figure 24 shows SRM Input and Output LEDs..
Refer to this table if a module Input / Output LED illuminates identifying the Function and Device.
SRM (Module) 1
Output LED Function Input LED Ign sw Enable Device
1 Rh cornering light 1/11,2/21 1/1,2/1,3/1 sw,rh turn/ent door open
2 Rh frt turn, rh frt side turn,rh frt int side turn,
rh rear side turn,rh turn tt/clapper 1/11,1/3 sw,rh turn
3 Frt upper markers,int side marker seat aisle lights 1/4, sw clearance light
4 rh lo beam 1/17, sw lo headlight
5 rh hi beam 1/16, sw hi beam
6 lh fog 2/23+1/17 1/1,2/1,3/1 sw fog lamp
7 back up alarm 1/20, 1/1,2/1,3/1 sw reverse
8 hi mount stop lights 1/21, sw service brake
9 spare
10 HVAC control 1/1,2/1,3/1
11 rh rear turn 1/11,1/3 sw,rh turn
12 rear upper marker interior blue running lights 1/4, sw clearance light
13 Back up lights 1/20, 1/1,2/1,3/1 sw reverse
14 kneel exhaust 1/25, 1/1,2/1,3/1 sw kneel
15 kneel fast recovery 1/26, 1/1,2/1,3/1 sw recover
16 kneel rec park brake cut off valve
17 kneel warning/light and buzzer 1/25, 1/1,2/1,3/1 sw kneel
18 spare
19 cruise service brake input
20 fast idle
SRM (Module) 2
Output LED Function Input LED Ign sw Enable Device
1 lh cornering light 2/11, 1/1,2/1,3/1 sw lh turn
2 lh frt turn,lh frt side turn,left frt int side turn,
lh turn tt/clapper 2/11,2/3 sw lh turn
3 lh lo beam 1/17, sw lo headlight
4 lh hi beam 1/16, sw hi beam
5 rh fog light 2/23+1/17 1/1,2/1,3/1 sw fog lamp
6 rh rear stop/lh rear stop 1/21, sw service brake
7 lh frt clr.rh frt clr,lh rear tail,rh rear tail,license plate 1/4, sw clearance light
8 lh rear turn 2/11, sw lh turn
9 spare
10 driver’s light 2/22, 1/1,2/1,3/1 sw driver’s light
11 steplight 2/13, 1/1,2/1,3/1 sw steplight
12 door claw 1/1,2/1,3/1
13 service lights 2/5, sw service lights
14 ecas service brake
15 starter 2/15, 1/1,2/1,3/1 sw crank
16 rear rise 2/12, 1/1,2/1,3/1 sw rear rise
17 tag unload 2/16, 1/1,2/1,3/1 sw tag unload
18 spare
19 shift inhibit
20 trans retarder status/fan control

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Input/Output LED Checklist --- continued

SRM (Module) 3
Output LED Function Input LED Ign sw Enable Device
1 lav light,fan/occ 1/1,2/1,3/1 sw ignition
2 lav heater 1/1,2/1,3/1 sw ignition
3 lh frt aisle light 2/12,2/24 1/1,2/1,3/1 sw aisle lights
4 lh rear aisle light 2/12,2/24 1/1,2/1,3/1 sw aisle lights
5 rh frt aisle light 2/12,2/24 1/1,2/1,3/1 sw aisle lights
6 rh rear aisle light 2/12,2/24 1/1,2/1,3/1 sw aisle lights
7 wcl lights 1/1,2/1,3/1
8 wcl control 1/1,2/1,3/1
9 spare
10 lh frt reading lights 3/19, 1/1,2/1,3/1 sw reading light master
11 lh rear reading lights 3/19, 1/1,2/1,3/1 sw reading light master
12 rh front reading lights 3/19, 1/1,2/1,3/1 sw reading light master
13 rh rear reading lights 3/19, 1/1,2/1,3/1 sw reading light master
14 baggage lights 3/4, sw baggage lights
15 air dryer 1/1,2/1,3/1 sw ignition
16 vacuum inverter enable 2/6,2/7 1/1,2/1,3/1 sw ignition , starter lockout
17 park brake interlock
18 spare
19 throttle disable
20 service brake status

FIGURE 24. Multiplex SRM Input / Output LEDs

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MUX Plug Location Chart

PLUG # SIZE LOCATION
F1 8 FUSE BOX/ BATTERY COMPT
F2 8 FUSE BOX/ BATTERY COMPT
F3 8 FUSE BOX/ BATTERY COMPT
F4 8 FUSE BOX /BATTERY COMPT
P---1A 23 MODULE/FRONT J BOX
P---1B 35 MODULE/FRONT J BOX
P---1C 35 MODULE/FRONT J BOX
P---2A 23 MODULE/FRONT J BOX
P---2B 35 MODULE/FRONT J BOX
P---2C 35 MODULE/FRONT J BOX
P---3A 23 MODULE/LH REAR PARCEL RACK
P---3B 35 MODULE/LH REAR PARCEL RACK
P---3C 35 MODULE/LH REAR PARCEL RACK
P---4 35 MODULE/LH FRONT SERVICE COMPT
P---5 35 MODULE/LH FRONT PARCEL RACK
P---27 48 BOTTOM/FRONT J BOX
P---28 .12---19 BOTTOM/FRONT J BOX
P---30 15 ABS BOX/REAR #1 BAGGAGE COMPT
P---31 .4---28 REAR OF FRONT J BOX
P---32 .4---28 BOTTOM/FRONT J BOX
P---33 48 BOTTOM/FRONT J BOX
P---34 12 ENTRANCE DOOR MODULE/REAR OF STEPWELL
P---35 19 FRONT BOGIE/SPARE TIRE COMPT
P---36 .4---28 ENGINE COMPT
P---37 31 TRANSMISSION PLUG ENGINE COMPT
P---38 .4---28 ENGINE COMPT
P---39 .4---28 ENGINE COMPT/REAR ROOF
P---40
P---41 36 FRONT J BOX
P---42 .4---28 REAR REMOTE BOX
P---43
P---44
P---45 19 FRONT J BOX
P---46 48 REAR BOGIE
P---47 19 LH FRONT BAGGAGE COMPT
P---48 19 RH FRONT BAGGAGE COMPT
P---49 .12---19 ENGINE COMPT
P---50 .12---19 ENGINE COMPT
P---51
P---52
P---53
P---54
P---55
P---56
P---57
P---58
P---59
P---60
P---61 12 ABS BOX/REAR #1 BAGGAGE COMPT
P---62 12 ABS BOX/REAR #1 BAGGAGE COMPT
P---63 12 ABS BOX/REAR #1 BAGGAGE COMPT
P---64 12 ABS BOX/REAR #1 BAGGAGE COMPT
P---65
P---66
P---67

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MUX Plug Location Chart --- Continued

P---68 .4---28 HVAC/ABOVE MAIN EVAPORATER
P---69 12 ENGINE COMPT
P---70 48 FRONT J BOX/DASH
P---71
P---72 15 FRONT J BOX
P---73
P---74 12 DRIVER’S HEATER BOX/RH HEADLIGHT
P---75
P---76
P---77
P---78
P---79
P---80 12 GND MODULE/BATTERY COMPT
P---81
P---82
P---83
P---84
P---85
P---86
P---87
P---88 12 GND MODULE/FRONT J BOX
P---89 12 GND MODULE/FRONT J BOX
P---90 12 GND MODULE/FRONT J BOX
P---91 9 GND MODULE/FRONT J BOX
P---92
P---93
P---94
P---95
P---96 32 TRANSMISSION ECU/BATTERY COMPT
P---97 32 TRANSMISSION ECU/BATTERY COMPT
P---98 32 TRANSMISSION ECU/BATTERY COMPT
P---99
P---100
P---101
P---102
P---103
P---104
P---105
P---106
P---107
P---108
P---109 12 SPARE TIRE COMPT
P---110 .4---28 BOTTOM/FRONT J BOX
P---111 6 ENGINE COMPT
P---112 20 INSTRUMENT PANEL
P---113 20 INSTRUMENT PANEL
P---114 24 INSTRUMENT PANEL
P---115 9 FRONT J BOX
P---116 12 FRONT J BOX
P---117
P---118 19 BATTERY COMPT
P---119 48 BATTERY COMPT

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 Date March 2003

SECTION 8
ENGINE
A1 -- Engine Installation: Detroit Diesel Series 60
A2 -- Engine Installation: Caterpillar
B -- Cold Weather Starting
C -- Jacobs Engine Brake System

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SECTION 8A1

ENGINE INSTALLATION
DETROIT DIESEL SERIES 60
CONTENTS OF THIS SECTION

SUBJECT PAGE
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8A1-2
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8A1-2
Engine Module Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8A1-3
Engine Module Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8A1-4
Lubrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8A1-4
Service and Inspection Intervals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8A1-4
Engine Mounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8A1-5
Torque Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8A1-6
Electronic Engine Control Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8A1-8
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8A1-8
Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8A1-7
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8A1-11
Diagnostics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8A1-11
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8A1-11
Welding Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8A1-13
Diagnostic Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8A1-15
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8A1-23
Service Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8A1-24

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ENGINE

ENGINE SIDE MOUNT

ENGINE CRADLE
ENGINE FRONT MOUNT

POWER MODULE

FIGURE 1

GENERAL DESCRIPTION the Detroit Diesel S60 Service Manual.

The Detroit Diesel Series 60 engine is a six-cylinder, NOTE: In the following engine maintenance
four-stroke, right-hand rotation, high speed, high torque procedures, left, right, forward and rear are used as
diesel engine. The engine is turbocharged, intercooled though looking at the engine from the rear engine
and electronically controlled by the DDEC IV module. service door. This convention is the opposite to
The basic engine is 400-hp which can be Detroit Diesel publications, in which the rear of the
programmed to 375-hp and 430-hp. engine is the flywheel end.

MAINTENANCE NOTE: Illustrations are typical. Differences may exist

For engine maintenance and repair information, see between the illustrations and the actual parts.

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ENGINE MODULE REMOVAL 12. Disconnect the air compressor discharge line from
The engine module (Figure 1), which includes the the air dryer coil.
engine, transmission, power steering pump, starter, 13. Disconnect the fuel supply and return lines from
alternator, isolators and cradle, can be removed from the the air/fuel junction block.
coach by the following sequence: 14. Remove the cradle U-bolts.
An engine dolly is recommended for the removal of 15. Disconnect the ground cable.
the engine module.
16. Disconnect the starter power cable.
1. Switch the main battery disconnect OFF.
17. Disconnect and label the alternator wiring.
2. Block the wheels of the front axle to ensure that the
coach does not move during the procedure. 18. Disconnect the two wire harness plugs at the rear
3. Remove the bumper and rear frame crossmember. bulkhead and tie-wrap the free end to the engine.
4. Drain the coolant. See Section 6. 19. Disconnect the WTEC main coach wire harness at
5. Vent the air system. See Section 4. the transmission.
6. Remove the fan drive and A/C belts. 20. Disconnect and label all coach water temperature
7. Remove the air intake and CAC tubes. See Section gauge and switch wire harnesses on the thermostat
6. housing.
8. Remove the exhaust tube. 21. Disconnect the driveshaft at the differential. See
9. Remove the auxiliary heater exhaust tube. Section 14.
10. Remove the auxiliary heater coolant tube. 22. Raise the coach.
(Figure 2) 23. Position the dolly under the engine.
24. Lower the coach.
COOLANT SUPPLY LINE

CAUTION
Because there is minimal clearance
between the engine and the top of the
engine compartment, lower the coach body
only enough to free the engine cradle.
Clearance between engine cradle and the
coach engine mounting rail should be 1/8 -
1/4 inch (3 - 6 mm).

FIGURE 2 25. Roll the dolly, with the engine module, out of the
11. Remove the coolant tubes. engine compartment.

THERMOSTAT
OUTLET PIPE

MAKE-UP WATER PIPE FRONT OF ENGINE

WATER PUMP INLET PIPE AND HOSE

FIGURE 3

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ENGINE MODULE INSTALLATION Lubricating Oil Specifications

1. To reinstall the engine module, assemble in the
reversed removal sequence. See the Torque Chart Lubricating Oil Recommendation
at the end of this section for torque values. API Service Code Classification SAE Grade
2. Refill the cooling system. CI-4 15W-40
3. Fill the fuel filters with clean diesel fuel, if the fuel
system was disassembled or drained. Policy on Lubricant Additives
4. Start the engine and check for oil pressure and MCI does not recommend or support the use of any
normal operation. supplementary lubricant additives.

5. Check fuel and cooling system connections for

leakage.
6. Check for proper tracking.
7. Test the operation of all engine controls and
accessories.
8. Run the engine to operating temperature.
9. Shut the engine off.
10. Check and top off all fluid levels as required.
11. Retorque the CAC clamps.

LUBRICATION

NOTE: The MCI warranty applicable to Series 60 diesel FIGURE 4. Oil Fill Tube
engines provides in part that the provisions of such
warranty shall not apply to any engine unit that has been
subject to misuse, negligence or accident. Malfunctions
attributable to neglect or failure to follow manufacturer’s
fuel or lubricating oil recommendations will not be
covered by MCI or DDC warranties.

Diesel Engine Lubricating Oil

Detroit Diesel Series 60 engines have an oil capacity
of 38 U.S. quarts (40 liters). Oil is added through the oil fill
tube (Figure 4).
Diesel engines require heavy-duty lubricating oils.
Basic requirements of such oils are lubricating quality,
high heat resistance and contaminant control. FIGURE 5. Oil Level Dipstick
The only lubricating oil recommended for Detroit
Diesel Series 60 diesel engines is the API Service SERVICE AND INSPECTION INTERVALS
Code CI4 and viscosity grade SAE 15W-40. Generally, the service intervals given in the Detroit
Diesel Service Manual are the minimum requirements to
Synthetic Oil keep the engine warranty valid. When determining
Synthetic oils may be used in Detroit Diesel engines, maintenance schedules, more frequent service intervals
provided they are API licensed and meet the should be considered for operating conditions that are
performance and chemical requirements of harsher than normal.
non-synthetic oils in the API Service Code CI4 and Lube oil sample analysis at regular drain intervals is
viscosity grade SAE 15W-40. The use of synthetic oil recommended to detect internal engine malfunctions
does not extend the oil drain interval recommended by before a costly catastrophic failure and a “coach down”
Detroit Diesel. occurs.

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ENGINE MOUNTING
The engine is mounted to the engine cradle with four CAUTION
sets of rubber mounts, two rear mounts attached to
mounts on each side of the flywheel housing (Figure 6),
and two front mounts attached to the trunnion plate on Do not use petroleum-based products to
lubricate the mounts.
each side of the crankshaft
Inspect these rubber mounts during routine
5. Gently lower the engine down onto engine cradle to
maintenance inspections and replace them if necessary.
set the mount correctly.
6. Install the lower engine mount snubber with a new
retaining washer, and hand tighten it with the full
NOTE: Replace mounts only as complete sets (i.e. weight of the engine bearing on the cradle
upper mount and lower snubber). Engine mounts assembly.
need retorquing when they are replaced. Replace
both front or rear mounts as required:
CAUTION
1. Switch the battery disconnect OFF.
Improper installation of the motor mounts
2. Block the wheels of one axle to ensure that the can contribute to excessive engine
coach does not move during the procedure. vibration. When installing new mounts,
3. Unfasten and remove the damaged mount’s leave the mount bolts loose until the engine
bolting, and loosen all other mount fasteners to can be run for a short time. If the engine is
accelerated a few times, the rubber mount
allow its removal.
will find its correct position and then the
4. Position a jack under the engine and lift it until it is mount bolts can be torqued and cotter keys
clear of the cradle and the mount can be removed. installed.
(See Section 3E.)

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TORQUE CHART
(FOR COMPLETE ENGINE SPECIFICATIONS REFER TO THE DETROIT DIESEL ENGINE SERVICE MANUAL.)

Item Description Torque Value

Lb-Ft Nm
1 Front Motor Mount Bolts (Rear of Coach) 180 244
2 Rear Motor Mount Bolts 225 305
3 Rear Motor Mount Strut-to-Engine Locknuts 43 - 54 58 - 73
4 Crankshaft Vibration Damper Bolts 134 - 155 182 - 210
5 Crankshaft Pulley Bolts 134 - 155 182 - 210
6 Oil Drain Plug 33 - 37 45 - 50
7 Alternator Belt Pulley Tensioning Bracket Bolts 75 - 93 101 - 126
8 Alternator Mounting Bracket Bolts 43 - 54 58 - 78
9 Starter Mounting Bolts 138 - 154 187 - 209
10 Air Compressor Housing-to-Gear Case Bolts 43 - 54 58 - 73
11 Adapter and Steering Pump-to-Gear Case Bolts 43 - 54 58 - 73

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ELECTRONIC ENGINE CONTROL SYSTEMS

GENERAL DESCRIPTION feedback regarding the start and end of injection for a
given cylinder.
Diesel engine electronic control systems operate by
receiving, processing and storing information from
sensors located throughout the engine and other related
components. Input from these and devices determines
the command signals issued to maintain the engine’s
environmental and economic operation.
The systems are responsible for the storage and
retrieval of vital engine information, the processing of
received data and the transmittal of command signals
that will achieve correct engine functions relating to
operation. The systems can be interconnected to other
electrically or electronically controlled components such
as transmissions and throttle devices. The following is a
list of functions or tasks that a typical engine control
system addresses:
1. Controlling the engine’s fuel injection function (i.e.,
timing and fuel metering), including transient fuel
control (smoke control).
2. Communication with the transmission control
system.
3. Monitoring of rated speed and power, torque FIGURE 1
shaping, engine governing, cold start logics,
engine oil, intake air and coolant temperatures.
The systems also have protection circuits that reduce NOTE: There are no user-serviceable parts within
power and shut down the engine completely in the event the ECM. If the ECM is defective, it must be replaced.
of a potentially damaging engine condition, such as low
oil pressure, low coolant level or high engine
The ECM is factory-programmed and is determined
temperature. The systems should incorporate a
by a specific engine/transmission/tire size and axle ratio
self-diagnostic feature, and may identify a fault or
combination. Reprogramming is required for any
potential problem by illuminating a telltale and an
change within a combination.
alarms. Fault codes are logged into the system’s
memory for later read-out by maintenance personnel. Allison Transmission Vehicle Interface Module
(VIM)
COMPONENTS Some transmissions’ links to the engine control
system’s ECM require a Vehicle Interface Module (VIM).
This interface enables engines and transmissions of
Engine Electronic Control Module (ECM)
different manufacture to communicate vehicle speed
The Electronic Control Module (ECM) is the micro from a VSS and other related information. Refer to Serial
processor-controlled electronic monitoring and storage Communication Interface (SCI) standards SAE J-1708
unit for an engine control system. The ECM unit mounts and J-1587. The VIM is located in the electrical
on the engine (Figure 1). compartment, in front of the right-hand side drive
The ECM can identify problem conditions within the wheels, in the A/C and DDEC/ATEC junction box.
engine by comparing input from the various sensors to a
set of parameters (calibration and design data) stored Transmission Vehicle Speed Sensor (VSS)
within the ECM. After processing the input, the ECM The Vehicle Speed Sensor (VSS) is located at the
sends high current command pulses to the injector transmission output shaft and provides input to the ECM
solenoids to initiate fuel injection. The ECM also receives regarding vehicle speed.

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Engine Electronic Unit Injectors (EUI) duration of solenoid valve closure (pulse width)
The Electronic Unit Injectors (EUI) (Figure 2) are determines quantity of fuel injected.
electronically-controlled solenoid-operated fuel
injectors mounted into the cylinder head above each
cylinder. The solenoid-operated poppet valve on each
EUI performs injection timing and fuel metering
functions.

SOLENOID VALVE
(CLOSED)

FIGURE 3

ELECTRONIC UNIT
INJECTOR

FIGURE 2

Pressurization of fuel inside the injector occurs by a SOLENOID VALVE

conventional cam-operated plunger. When the solenoid (OPEN)
valve on the EUI is closed, fuel is pressurized and
injection is initiated at the beginning of injection (BOI)
(Figure 3).
1215
When the solenoid valve on the EUI is open, pressure
decreases and fuel injection ends (Figure 4). The FIGURE 4

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Throttle Position Sensor (TPS) sound an alarm and initiate the engine protection
The Throttle Position Sensor (TPS) (Figure 5) is sequence and shut-down procedure.
located in the electronic foot pedal assembly (EFPA) and
converts the throttle position into a signal usable by the
ECM. This sensor, in effect, replaces the mechanical
linkage from the accelerator treadle to the engine.

FIGURE 6. Oil Pressure Sensor

Oil Temperature Sensor (OTS)

The Oil Temperature Sensor (OTS) (Figure 7) is in the
engine oil gallery at rear RH side of the block below the
OPS.

FIGURE 5

Turbocharged Boost Sensor (TBS)

The Turbocharged Boost Sensor (TPS) is located
between the turbocharger discharge and the blower,
and monitors turbocharger compressor discharge
pressure. The TBS provides a signal to the ECM during
engine operation for transient smoke control.

Oil Pressure Sensor (OPS)

The Oil Pressure Sensor (OPS) (Figure 6) is located at
the rear RH side of block above the OTS. The OPS
monitors oil pressure in the engine and, if engine oil
pressure falls below a specified minimum value, the
ECM alerts the driver by lighting the “CHECK ENGINE” FIGURE 7. Oil Temperature Sensor
telltale and/or the “STOP ENGINE” telltale. The ECM will

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Coolant Temperature Sensor (CTS)

The Coolant Temperature Sensor (CTS) monitors LOW LEVEL SENSOR
engine coolant temperature, and is mounted in the
engine thermostat housing (Figure 8). Additionally, the OVERFLOW TUBE VALVE

CTS input may be used in the cold start logic feature of

some electronic control systems’ ECM.
If the coolant temperature exceeds the specified
maximum the ECM will light the “CHECK ENGINE”
telltale. If the coolant temperature exceeds the ECU
shut-down parameters, the “STOP ENGINE” telltale will SHUT DOWN SENSOR

light. The ECM will initiate the engine protection SIGHT GLASS
sequence, and begin engine shut-down.
NOTE: For more information on the engine
FIGURE 9
protection sequence see Diagnostics.

Coolant Level Sensor (CLS)

There are two Coolant Level Sensors, located in the
surge tank. One sends a Low Level warning to the driver, Air Temperature Sensor (ATS)
and the other causes the engine to shut down. The The Air Temperature Sensor (ATS) monitors intake
assembly is made up of a sensor probe and module. manifold air temperature to attain input for charge-air
The CLS probe is located near the bottom of the clutch fan control (Figure 10). Additionally, the ATS input
radiator’s surge tank, and monitors the coolant level may be used in the cold start logic feature of some
(Figure 9). electronic control systems (ECM).

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MAINTENANCE NOTE: This should give the driver enough power to

move the coach to a safe place where it can be shut
DIAGNOSTICS down.
Electronic engine control system diagnostic features
e. After thirty seconds all fuel is cut off completely.
can be separated into three areas: Engine Performance
Diagnostics, Self-Diagnostics and Engine System The engine overrule switch is provided on the driver’s
Protection. upper left-hand switch panel. The switch will allow an
additional thirty seconds of fuel before shutdown
Engine Performance Diagnostics occurs. The overrule switch is designed so that it
The system continuously monitors various sensors CANNOT be held “ON” to continuously overrule
and adjusts injector timing and fuel quantity input shutdown.
(depending on programming and sensor input) to If the engine protection feature is triggered, it will
provide optimum performance and minimal acceleration remain active until the fault goes away or the system is
smoke under all operating conditions. Cold weather reset. The DDEC system can be reset by parking the
starting is improved by matching the fuel input and coach, shutting off the ignition, waiting ten seconds and
timing to the ambient air temperature. then restarting the engine.
System Self-Diagnostics If the fault was temporary, the telltale panel indicator
The system continuously monitors itself and all lights will go out and normal operation will resume. A
fault code will be logged in memory until the memory is
related wiring for faults. If a fault is detected, the “CHECK
ENGINE” and/or “STOP ENGINE” telltale(s) will light cleared. The memory may be cleared by use of a DDR
(Figure 11). The fault may also be cleared by restarting
(depending on the severity of the fault), and if the fault is
in the main microprocessor, a backup microprocessor the engine ten times without the fault being relogged.
takes control.
If the fault remains after the engine is restarted, the
When the system is under the control of the backup problem is not temporary, and maintenance or repair of
microprocessor the engine will continue to function the problem is indicated.
normally. However, fuel injector control logic is based on
the following sensor input information:
Coolant Overtemperature Protection (COP)
1. Throttle Position Sensor (TPS). The COP feature protects the engine from excessive
2. Vehicle Speed Sensor (VSS). coolant overtemperature conditions by automatically
3. Turbocharger Boost Sensor (TBS). reducing engine power when the coolant temperature
4. Coolant Temperature Sensor (CTS). exceeds 215oF (101.6oC).
All other sensor input is ignored and a generic set of If the cause of the overtemperature is temporary, such
calibration data is substituted which may degrade as climbing a severe grade, the amount of available
engine performance while in the backup mode. Auxiliary power will be increased as the temperature decreases,
features which remain operational during backup mode with 100% power available as soon as the temperature
are the engine protection feature and accessary drops to 215oF (101.6oC). At approximately 221oF
equipment pulse width modulation. (203.2oC) the check engine light (CEL) will be activated.
If a severe cooling system problem exists, such as a
Engine Protection (With Shutdown Sequence) broken fan belt, and temperature continues to increase
When the engine protection feature is initiated, the in spite of the power reduction, the stop engine light
“CHECK ENGINE” and “STOP ENGINE” telltales in the (SEL) will be activated at 225F (107.2C). To assure that
center instrument cluster are illuminated. A fault code is adequate power is available to move the coach under
logged into the ECM’s memory and the following power emergency conditions, the COP feature will not reduce
reduction sequence is begun. the amount of available throttle to less than 50%. If the
a. Five seconds after fault detection power is reduced engine overheating continues, programmed engine
to 84% of current throttle. shutdown will occur.
b. Ten seconds after fault detection power is reduced
to 68% of current throttle. TROUBLESHOOTING
c. Fifteen seconds after fault detection power is The replacement of any internal engine components
reduced to 53%of current throttle. should be based on diagnostic codes indicating faulty
d. Seventeen seconds after fault detection power is components. Refer to the applicable system’s
reduced to 40% of current throttle. No further trouble-shooting manual and/or the appropriate
reduction of power occurs past 40% throttle. instruction manual for the diagnostic data reader being

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 Date March 2003 Page 8A1-12

used for complete information on diagnosis of The Diagnostic Data Link (DDL) connectors are
components. installed on the coach and enable the user to connect a
Troubleshooting the DDEC systems can be divided DDR to access and interpret the fault codes logged into
into the following two areas. the ECM’s memory and/or operational data.
1. Mechanical checks such as wiring and connector One of the two DDL connectors is located in the rear
problems. junction box, on the bottom side. The other connector is
2. Proper use of the DDR, and interpreting the logged located on the right-hand side, under the dash on the
codes. driver’s side.
Mechanical Checks The DDR should be able to electronically
Mechanical checks involve checking all wiring and troubleshoot all DDEC system components and related
connectors for proper connection, dirty or corroded wiring. Operation of the DDR should be in accordance
terminals and visual inspection of components for loose, with the “Diagnostic Data Reader User’s Manual”. Refer
damaged, or missing parts. to the instruction book provided for complete diagnostic
All wiring is Teflon-coated with crimp-type procedures.
connectors. Solder-type connectors are not used nor If a DDR is not immediately available, the fault codes
recommended on wiring, because normal vibration will logged in the ECM’s memory can be interpreted by use
cause the solder connection to fail in time. of the “CHECK ENGINE” switch on the upper front of the
DDEC control panel in the A/C DDEC/ATEC junction
Diagnostic Data Reader
The Diagnostic Data Reader (DDR) is a hand-held box, or the diagnostic switch on the LH switch panel.
Turn the switch on and note the flashing light on the
electronic device that can be connected to either of the
two DDLs for accessing and reviewing logged fault telltale panel. The light should flash a sequence of codes
which identify the faulty component or system. For
codes (Figure 11).
example, if the light flashes once, then pauses and
flashes three more times, this would indicate a fault code
13, which is interpreted as a problem with the coolant
level sensor.
Refer to the DDEC Troubleshooting Guide for a
complete listing of the fault codes and their meanings.

7403

FIGURE 11

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CAUTION
CAUTION
WELDING PROCEDURES
Improper welding can destroy electrical components. Read and make sure you understand the following
information before doing any welding. The following precautions and requirements must be followed.

1. Welding must be done only by a qualified and experienced person.

2. Position adequate ground contacts and barriers as close as possible to the weld area and as required to
protect components ( wiring, brake lines, hydraulic lines, etc. ) from damage due to heat or contact by
weld splatter, arcing, or other potentially damaging events associated with welding.
Note: DO NOT DISCONNECT BATTERY GROUND CABLE
3. Switch the main battery disconnect switch to OFF.
4. DISCONNECT THE FOLLOWING:

BATTERY COMPARTMENT:

a. Unplug the battery charger from the AC supply

b. All connectors from the WTEC ECU
c. All connectors from the HVAC controller
d. All connectors from ground module
e. 24 volt cable at battery

ENGINE COMPARTMENT:

a. P-36 and P-50 ( engine adaptor harness )

RH BAGGAGE COMPARTMENT:

a. Four large bulkheads connectors

FRONT JUNCTION BOX

a. All dash connectors

b. Two connectors on relay modules

5. When welding is done, reconnect the items in reverse order. Warn persons in the immediate area before
closing ( pulling ) the main disconnect switch.

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DIAGNOSTIC CODES
SERIES 60 DIAGNOSTIC CODES

FIRST SECOND PID SID FMI CAUSE

FLASH FLASH
1 1 187 -- 4 Variable Speed Governor Sensor Voltage Low
187 -- 7 Variable Speed Governor Switch System Not Re-
sponding
1 2 187 -- 3 Variable Speed Governor Sensor Voltage High
1 3 111 -- 4 Coolant Level Sensor Input Voltage Low
111 -- 6 Add Coolant Level Sensor Input Voltage Low
1 4 52 -- 3 Intercooler Coolant Temperature Sensor Input Voltage
High
110 -- 3 Coolant Temperature Sensor Input Voltage High
175 -- 3 Oil Temperature Sensor Input Voltage High
1 5 52 -- 4 Intercooler Coolant Temperature Sensor Input Voltage
Low
110 -- 4 Coolant Temperature Sensor Input Voltage Low
175 -- 4 Oil Temperature Sensor Input Voltage Low
1 6 111 -- 3 Coolant Level Sensor Input Voltage High
111 -- 5 Add Coolant Level Sensor Input Voltage High
1 7 51 -- 3 Throttle Plate Position Sensor Input Voltage High
72 -- 3 Blower Bypass Position Input Voltage High
1 8 51 -- 4 Throttle Plate Position Sensor Input Voltage Low
72 -- 4 Blower Bypass Position Input Voltage Low
2 1 91 -- 3 Throttle Position Sensor Input Voltage High
2 2 91 -- 4 Throttle Position Sensor Input Voltage Low
2 3 174 -- 3 Fuel Temperature Sensor Input Voltage High
-- 65 3 Oxygen Content Circuit Input Voltage High
2 4 174 -- 4 Fuel Temperature Sensor Input Voltage Low
-- 65 4 Oxygen Content Circuit Input Voltage Low
2 5 -- -- -- Reserved for “No Codes”
2 6 -- 25 11 Aux. Shutdown #1 Active
-- 61 11 Aux. Shutdown #2 Active
2 7 105 -- 3 Intake Manifold Temperature Sensor Input Voltage
High
171 -- 3 Ambient Air Temperature Sensor Input Voltage High
172 -- 3 Air Temperature Sensor Input Voltage High
2 8 105 -- 4 Intake Manifold Temperature Sensor Input Voltage
Low
171 -- 4 Ambient Air Temperature Sensor Input Voltage Low
172 -- 4 Air Temperature Sensor Input Voltage Low

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SERIES 60 DIAGNOSTIC CODES (CONT’D)

2 9 404 -- 4 Turbo Compressor Temperature Out Sensor Input Volt-

age Low (Release 32.0 or later)
3 1 -- 51 3 Aux. Output #3 Open Circuit (HIgh Side) - S3
-- 51 4 Aux. Output #3 Short To Ground (High Side - S3
-- 51 7 Aux. Output #3 Mechanical System Fail - S3
-- 52 3 Aux. Output #4 open Circuit (High Side) - T3
-- 52 4 Aux. Output #4 Short To Ground (High Side) - T3
-- 52 7 Aux. Output #4 Mechanical System Failure - T3
3 2 -- 238 3 SEL Short to Battery (+)
-- 238 4 SEL Open Circuit
-- 239 3 CEL Short to Battery (+)
-- 239 4 CEL Open Circuit
3 3 102 -- 3 Turbo Boost Pressure Sensor Input Voltage High
3 4 102 -- 4 Turbo Boost Pressure Sensor Input Voltage Low
3 5 19 -- 3 High Range Oil Pressure Sensor Input Voltage High
100 -- 3 Oil Pressure Sensor Input Voltage Low
3 6 19 -- 4 High Range Oil Pressure Sensor Input Voltage High
100 -- 4 Oil Pressure Sensor Input Voltage Low
3 7 18 -- 3 High Range Fuel Pressure Sensor Input Voltage High
94 -- 3 Fuel Pressure Sensor Input Voltage High
95 -- 3 Fuel Restriction Sensor Input Voltage High
3 8 18 -- 4 High Range Fuel Pressure Sensor Input Voltage Low
94 -- 4 Fuel Pressure Sensor Input Voltage Low
95 4 Fuel Restriction Sensor Input Voltage Low
3 9 -- 152 7 EGR Valve Not Responding (Release 29.0 or later)
-- 153 7 VNT Vanes Not Responding (Release 29.0 or later)
4 1 -- 21 0 Too Many SRS (missing TRS)
4 2 -- 21 1 Too Few SRS (missing SRS)
4 3 111 -- 1 Coolant Level Low
4 4 52 -- 0 Intercooler Coolant Temperature High
4 4 105 -- 0 Intake Manifold Temperature High
110 -- 0 Coolant Temperature High
172 -- 0 Air Inlet Temperature High
175 -- 0 Oil Temperature High
4 5 19 -- 1 High Range Oil Pressure Low
100 -- 1 Oil Pressure Low
4 6 168 -- 1 ECM Battery Voltage Low
-- 214 1 RTC Backup Battery Voltage Low (Release 29.0 or lat-
er)
-- 232 1 Sensor Supply Voltage Low

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SERIES 60 DIAGNOSTIC CODES (CONT’D)

4 6 -- 232 1 Sensor Supply Voltage Low

4 7 18 -- 0 High Range Fuel Pressure High
94 -- 0 Fuel Pressure High
102 -- 0 Turbo Boost Pressure High
106 -- 0 Air Inlet Pressure High
164 -- 0 Injection Control Pressure High
4 8 18 -- 1 High Range Fuel Pressure Low
94 -- 1 Fuel Pressure Low
106 -- 1 Air Inlet Pressure Low
164 -- 1 Injection Control Pressure Low
404 -- 1 Turbo Compressor Temperature Out High (Release
32.0 or later)
-- 154 1 EGR Temperature Low (Release 29.0 or later)
-- 155 1 EGR Delta Pressure Low (Release 29.0 or later)
4 9 404 -- 0 Turbo Compressor Out Temperature High (Release
32.0 or later)
5 1 404 -- 3 Turbo Compressor Out Temperature Sensor Input Volt-
age High (Release 32.0 or later)
5 2 -- 254 12 A/D Conversion Fail
5 3 -- 253 2 Nonvolatile Checksum Incorrect
-- 253 12 EEPROM Write Error
-- 253 13 Out of Calibration
5 4 84 -- 12 Vehicle Speed Sensor Fault
5 5 -- 216 14 Other ECU fault (Release 27.0 or later) (This fault is
logged in conjunction with another fault to indicate miss-
ing information from another ECU.)
-- 231 12 J1939 Data Link Fault
-- 248 8 Proprietary Data Link Fault (Master)
-- 248 9 Proprietary Data Link Fault (Receiver)
5 6 -- 250 12 J1587 Data Link Fault
5 7 -- 249 12 J1922 Data Link Fault
5 8 92 -- 0 Torque Overload
6 1 -- xxx 0 Injector xxx Response Time Long
6 2 -- 26 3 Aux. Output #1 Short to Battery (+) - F3
-- 26 4 Aux. Output #1 Open Circuit - F3

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SERIES 60 DIAGNOSTIC CODES (CONT’D)

6 2 -- 26 7 Aux. Output #1 Mechanical System Not Responding

Properly - F3
-- 40 3 Aux. Output W2 Short to Battery (+) - A2
-- 40 4 Aux. Output #2 Open Circuit - A2
-- 40 7 Aux. Output W2 Mechanical System Not Responding
Properly - A2
-- 53 3 Aux. Output #5 Short to Battery (+) - W3
-- 53 4 Aux. Output W5 Open Circuit - W3
-- 53 7 Aux. Output #5 Mechanical system Not Responding
Properly - W3
-- 54 3 Aux. Output #6 Short to Battery (+) - X3
-- 54 4 Aux. Output #6 Open Circuit - X3
-- 54 7 Aux. Output #6 Mechanical System Not Responding
Properly - X3
-- 55 3 Aux. Output #7 Short to Battery (+) - Y3
-- 55 4 Aux. Output #7 Open Circuit - Y3
-- 55 7 Aux. Output #7 Mechanical System Not Responding
Properly - Y3
-- 56 3 Aux. Output #8 Short to Battery (+) - A1
-- 56 4 Aux. Output #8 Open circuit - A1
-- 56 7 Aux. Output #8 Mechanical System Not Responding
Properly - A1
6 3 -- 57 0 PWM #1 Above Normal Range
-- 57 1 PWM #1 Below Normal Range
-- 57 3 PWM #1 Short to Battery (+)
-- 57 4 PWM #1 Open Circuit
-- 58 0 PWM #2 Above Normal Range
-- 58 1 PWM #2 Below Normal Range
-- 58 3 PWM #2 Short to Battery (+)
-- 58 4 PWM #2 Open Circuit
-- 59 0 PWM #3 Above Normal Range
-- 59 1 PWM #3 Below Normal Range
-- 59 3 PWM #3 Short to Battery (+)
-- 59 4 PWM #3 Open Circuit
-- 60 0 PWM #4 Above Normal Range
-- 60 1 PWM #4 Below Normal Range
-- 60 3 PWM #4 Short to Battery (+)
-- 60 4 PWM #4 Open circuit
6 4 103 -- 0 Turbo Overspeed
103 -- 8 Turbo Speed Sensor Input Failure

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SERIES 60 DIAGNOSTIC CODES (CONT’D)

6 5 51 -- 0 Throttle Plate Position Above Normal Range

51 -- 1 Throttle Plate Position Below Normal Range
51 -- 2 Throttle Plate Position Erratic
51 -- 7 Throttle Plate Not Responding
107 -- 3 Air Filter Restriction Sensor Voltage High
107 -- 4 Air Filter Restriction Sensor Voltage Low
6 6 99 -- 3 Oil Filter Restriction Sensor Voltage High
99 -- 4 Oil Filter Restriction Sensor Voltage Low
-- 76 0 Engine Knock Level Above Normal Range
-- 76 3 Engine Knock Level Sensor Input Voltage High
-- 76 4 Engine Knock Level Sensor Input Voltage Low
-- 76 7 Engine Knock Level Sensor Not Responding
6 7 20 -- 3 High Range Coolant Pressure Sensor Input Voltage
High
20 -- 4 High Range Coolant Pressure Sensor Input Voltage
Low
106 -- 3 Air Inlet Pressure Sensor Input Voltage High
106 -- 4 Air Inlet Pressure Sensor Input Voltage Low
109 -- 3 Coolant Pressure Sensor Input Voltage High
109 -- 4 Coolant Pressure Sensor Input Voltage Low
6 8 -- 230 5 TPS Idle Validation Circuit Fault (open circuit)
-- 230 6 TPS Idle Validation Circuit Fault (short to ground)
7 1 -- xxx 1 Injector xxx Response Time Short
7 2 84 -- 0 Vehicle Overspeed
84 -- 11 Vehicle Overspeed (Absolute)
-- 65 0 Oxygen Content Too High
-- 65 1 Oxygen Content Too Low
7 3 107 -- 0 Air Filter Restriction High
-- 77 0 Gas Valve Position Above Normal Range
-- 77 1 Gas Valve Position Below Normal Range
-- 77 3 Gas Valve Position Input Voltage High
-- 77 4 Gas Valve Position Input Voltage Low
-- 77 7 Gas Metering Valve Not Responding
-- 151 14 ESS Transmission Stuck in Gear
-- 226 11 Transmission Neutral Switch Failure (ESS Transmis-
sion)
-- 227 2 Aux Analog Input Data Erratic, Intermittent, or Incor-
rect (ESS Transmission)
-- 227 3 Aux Analog Input #1 Voltage High (ESS Transmission)
-- 227 4 Aux Analog Input #1 Voltage Low (ESS Transmission)

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SERIES 60 DIAGNOSTIC CODES (CONT’D)

7 4 70 -- 4 Optimized Idle Safety Loop Short to Ground

99 -- 0 Oil Filter Restriction High
7 5 168 -- 0 ECM Battery Voltage High
-- 214 0 RTC Backup Battery Voltage High (Release 29.0 or
later)
-- 232 0 Sensor supply Voltage High
7 6 121 -- 0 Engine Overspeed With Engine Brake
7 7 3 -- 0 Cylinder Head Temperature High
19 -- 0 High Range Oil Pressure High
20 -- 0 High Range Coolant Pressure High
72 -- 0 Blower Bypass Door Position High
72 -- 1 Blower Bypass Door Position Low
73 -- 1 Fire Pump Pressure Low
81 -- 0 Exhaust Back Pressure High
81 -- 1 Exhaust Back Pressure Low
81 -- 3 Exhaust Back Pressure Sensor Voltage High
81 -- 4 Exhaust Back Pressure Sensor Voltage Low
81 -- 12 Exhaust Back Pressure at Rampdown Threshold
95 -- 1 Fuel Filter Differential Pressure Low
99 -- 1 Oil Filter Differential Pressure Low
100 -- 0 Engine Oil Pressure High
102 -- 1 Turbo Boost Pressure Low
105 -- 1 Inlet Manifold Temperature Low
107 -- 1 Air Filter Restriction Pressure Low
108 -- 0 Barometric Pressure High
108 -- 1 Barometric Pressure Low
109 -- 0 Coolant Pressure High
110 -- 1 Coolant Temperature Low
111 -- 0 Coolant Level High
171 -- 0 Ambient Air Temperature High
171 -- 1 Ambient Air Temperature Low
172 -- 1 Air Inlet Temperature Low
174 -- 0 Fuel Temperature High
174 -- 1 Fuel Temperature Low
175 -- 1 Engine Oil Temperature Low
222 -- 14 Anti-Theft Fault Present

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SERIES 60 DIAGNOSTIC CODES (CONT’D)

7 7 251 -- 10 Clock Module Abnormal Rate of Change

251 -- 13 Clock Module Failure
252 -- 10 Clock Module Abnormal Rate of Change
222 -- 14 Anti-Theft Fault Present
251 -- 10 Clock Module Abnormal Rate of Change
251 -- 13 Clock Module Failure
252 -- 10 Clock Module Abnormal Rate of Change
252 -- 13 Clock Module Failure
-- 151 11 Service Now Lamp Fault Expiration (Release 32.0 or
7 8 86 -- 14 later)
Cruise Control/Adaptive Cruise Control Fault (Release
27.0 or later)
8 1 98 -- 3 Oil Level Sensor Input Voltage High
101 -- 3 Crankcase Pressure Sensor Input Voltage High
153 -- 3 Extended Crankcase Pressure Input Voltage High (Re-
lease 27.0 or later)
164 -- 3 Injection Control Pressure Sensor Input Voltage High
173 -- 3 Exhaust Temperature Sensor Input Voltage High
-- 129 3 Exhaust Port Temperature #1 Sensor Voltage High
(Release 32.0 or later)
-- 130 3 Exhaust Port Temperature #2 Sensor Voltage High
(Release 32.0 or later)
-- 131 3 Exhaust Port Temperature #3 Sensor Voltage High
(Release 32.0 or later)
-- 132 3 Exhaust Port Temperature #4 Sensor Voltage High
(Release 32.0 or later)
-- 133 3 Exhaust Port Temperature #5 Sensor Voltage High
(Release 32.0 or later)
-- 134 3 Exhaust Port Temperature #6 Sensor Voltage High
(Release 32.0 or later)
-- 135 3 Exhaust Port Temperature #7 Sensor Voltage High
(Release 32.0 or later)
-- 136 3 Exhaust Port Temperature #8 Sensor Voltage High
(Release 32.0 or later)
-- 137 3 Exhaust Port Temperature #9 Sensor Voltage High
(Release 32.0 or later)
-- 138 3 Exhaust Port Temperature #10 Sensor Voltage High
(Release 32.0 or later)
-- 139 3 Exhaust Port Temperature #11 Sensor Voltage High
(Release 32.0 or later)
-- 140 3 Exhaust Port Temperature #12 Sensor Voltage High
(Release 32.0 or later)
-- 141 3 Exhaust Port Temperature #13 Sensor Voltage High
(Release 32.0 or later)

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SERIES 60 DIAGNOSTIC CODES (CONT’D)

8 1 -- 142 3 Exhaust Port Temperature #14 Sensor Voltage High

(Release 32.0 or later)
-- 143 3 Exhaust Port Temperature #15 Sensor Voltage High
(Release 32.0 or later)
-- 144 3 Exhaust Port Temperature #16 Sensor Voltage High
(Release 32.0 or later)
-- 154 3 EGR Temperature Input Voltage High (Release 29.0 or
later)
-- 155 3 EGR Delta Pressure Input Voltage Low (Release 29.0
or later
8 2 98 -- 4 Oil Level Sensor Input Voltage Low
101 -- 4 Crankcase Pressure Sensor Input Voltage Low
153 -- 4 Extended Crankcase Pressure Input Voltage Low (Re-
lease 27.0 or later)
164 -- 4 Injection Control Pressure Sensor Input Voltage Low
173 -- 4 Exhaust Temperature Sensor Input Voltage Low
-- 129 4 Exhaust Port Temperature #1 Sensor Voltage Low
(Release 32.0 or later)
-- 130 4 Exhaust Port Temperature #2 Sensor Voltage Low
(Release 32.0 or later)
-- 131 4 Exhaust Port Temperature #3 Sensor Voltage Low
(Release 32.0 or later)
-- 132 4 Exhaust Port Temperature #4 Sensor Voltage Low
(Release 32.0 or later)
-- 133 4 Exhaust Port Temperature #5 Sensor Voltage Low
(Release 32.0 or later)
-- 134 4 Exhaust Port Temperature #6 Sensor Voltage Low
(Release 32.0 or later)
-- 135 4 Exhaust Port Temperature #7 Sensor Voltage Low
(Release 32.0 or later)
-- 136 4 Exhaust Port Temperature #8 Sensor Voltage Low
(Release 32.0 or later)
-- 137 4 Exhaust Port Temperature #9 Sensor Voltage Low
(Release 32.0 or later)
-- 138 4 Exhaust Port Temperature #10 Sensor Voltage Low
(Release 32.0 or later)
-- 139 4 Exhaust Port Temperature #11 Sensor Voltage Low
(Release 32.0 or later)
-- 140 4 Exhaust Port Temperature #12 Sensor Voltage Low
(Release 32.0 or later)
-- 141 4 Exhaust Port Temperature #13 Sensor Voltage Low
(Release 32.0 or later)

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SERIES 60 DIAGNOSTIC CODES (CONT’D)

8 2 -- 142 4 Exhaust Port Temperature #14 Sensor Voltage Low

(Release 32.0 or later)
-- 143 4 Exhaust Port Temperature #15 Sensor Voltage Low
(Release 32.0 or later)
-- 144 4 Exhaust Port Temperature #16 Sensor Voltage Low
(Release 32.0 or later)
-- 154 4 EGR Temperature Input Voltage Low (Release 29.0 or
later)
-- 155 4 EGR Delta Pressure Input Voltage High (Release 29.0
or later)
8 3 73 -- 0 Pump Pressure High
98 -- 0 Oil Level High
101 -- 0 Crankcase Pressure High
153 -- 0 Extended Crankcase Pressure High (Release 27.0 or
later)
173 -- 0 Exhaust Temperature high
-- 129 0 Exhaust Port Temperature #1 Sensor Voltage High
(Release 32.0 or later)
-- 130 0 Exhaust Port Temperature #2 Sensor Voltage High
(Release 32.0 or later)
-- 131 0 Exhaust Port Temperature #3 Sensor Voltage High
(Release 32.0 or later)
-- 132 0 Exhaust Port Temperature #4 Sensor Voltage High
(Release 32.0 or later)
-- 133 0 Exhaust Port Temperature #5 Sensor Voltage High
(Release 32.0 or later)
-- 134 0 Exhaust Port Temperature #6 Sensor Voltage High
(Release 32.0 or later)
-- 135 0 Exhaust Port Temperature #7 Sensor Voltage High
(Release 32.0 or later)
-- 136 0 Exhaust Port Temperature #8 Sensor Voltage High
(Release 32.0 or later)
-- 137 0 Exhaust Port Temperature #9 Sensor Voltage High
(Release 32.0 or later)
-- 138 0 Exhaust Port Temperature #10 Sensor Voltage High
(Release 32.0 or later)
-- 139 0 Exhaust Port Temperature #11 Sensor Voltage High
(Release 32.0 or later)
-- 140 0 Exhaust Port Temperature #12 Sensor Voltage High
(Release 32.0 or later)
-- 141 0 Exhaust Port Temperature #13 Sensor Voltage High
(Release 32.0 or later)
-- 142 0 Exhaust Port Temperature #14 Sensor Voltage High
(Release 32.0 or later)
-- 143 0 Exhaust Port Temperature #15 Sensor Voltage High
(Release 32.0 or later)

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SERIES 60 DIAGNOSTIC CODES (CONT’D)

8 3 -- 144 0 Exhaust Port Temperature #16 Sensor Voltage High

(Release 32.0 or later)
-- 154 0 EGR Gas Temperature High (Release 29.0 or later)
-- 155 0 EGR Delta Pressure High (Release 29.0 or later)
8 4 98 -- 1 Oil Level Low
101 -- 1 Crankcase Pressure Low
153 -- 1 Extended Crankcase Pressure Low (Release 27.0 or
later)
8 5 190 -- 0 Engine Overspeed
190 -- 14 Engine Overspeed Signal (Release 28.0 or later)
8 6 73 -- 3 Pump Pressure Sensor Input Voltage High
108 -- 3 Barometric Pressure Sensor Input Voltage High
8 7 73 -- 4 Pump Pressure Sensor Input Voltage Low
108 -- 4 Barometric Pressure Sensor Input Voltage Low
8 8 20 -- 1 High Range Coolant Pressure Low
109 -- 1 Coolant Pressure Low
8 9 95 -- 0 Fuel Restriction High
111 -- 12 Maintenance Alert Coolant Level Fault

SPECIFICATIONS

DETROIT DIESEL 400-HP SERIES 60 ENGINE

Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 cycle
Number of Cylinders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Bore . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.12 inches (130 mm)
Stroke . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3 inches (160 mm)
Compression Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.5:1
Total Displacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 788 in# (12.7 L)
Rated Full Load Speed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2100 RPM
OIL FILTER ASSEMBLY (TWO FILTER SYSTEM)
Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Spin-On Full-Flow (28 Micron)
Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (Filter Head Mounted) LH Side of Coach
FUEL FILTER ASSEMBLY
Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Spin-On
Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (Filter Head Mounted) RH Side of Coach
WATER CHARGE FILTER ASSEMBLY
Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Spin-On
Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (Filter Head Mounted) LH Side of Coach

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SERVICE TOOLS
SOME TOOLS LISTED IN THIS SECTION ARE SPECIALLY DESIGNED TO MEET THE
NEEDS OF VARIOUS SERVICE OPERATIONS. THEY ARE AVAILABLE FOR PURCHASE
THROUGH MCI SERVICE PARTS OR, WHERE PRACTICAL, MAY BE MANUFACTURED
BY THE OPERATOR. DRAWINGS ARE AVAILABLE UPON REQUEST.

J9737.5
DIAL INDICATOR
J8001.2 SWIVEL CLAMP

J29893.2
UNIVERSAL J29893.1
ATTACHMENT BODY ASSEMBLY

HOUSING
GEAR
5311

Dial Indicator and Mounting Tool

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SECTION 8A2

ENGINE INSTALLATION
CATERPILLAR C-12
CONTENTS OF THIS SECTION

SUBJECT PAGE
Engine Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8A2-2
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8A2-2
Lubrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8A2-3
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8A2-4
Electronic Engine Control Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8A2-6
General Descripiton . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8A2-6
Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8A2-6
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8A2-9
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8A2-9
Diagnostic Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8A2-11
Troque Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8A2-13

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FIGURE 1

ENGINE ASSEMBLY

GENERAL DESCRIPTION full pressure lubrication is supplied to all main,

connecting rod bearings and other moving parts within
The Caterpillar C-12 is a four-stroke cycle, right hand the engine. A gear-type pump draws oil from the oil pan
rotation, high speed high torque (380 HP) engine. These through an intake screen and delivers it to the oil filter,
engines utilize a turbo-charged air intake manifold for from the filter, a small portion is delivered to the
optimum engine aspiration, and Caterpillar’s electronic turbocharger by an external oil line. The remainder of the
control system for efficient operation. filtered oil is delivered to the oil cooler, or bypasses the
The caterpillar C-12 utilizes an in-line cast iron block, cooler, and enters the block’s oil gallery. This gallery
together with a cast iron head. Each engine module is feeds oil to the camshaft bearings and rocker
equipped with an oil cooler, one fuel filter assembly, a assemblies, and the remainder lubricates the main and
starting motor, air compressor, water pump, charge connecting rod bearings.
water filter, turbocharger and the electronic engine Coolant is circulated through the engine by a
control system. additionally, the engine is fitted with a centrifugal-type water pump. The cooling system,
single combination full-flow/ by-pass oil filter and oil including the radiator and surge tank, is a closed-type
cooler assembly. system. Heat is removed from the coolant by the

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radiator. Control of the engine temperature is This is opposite to the position of these parts with
accomplished by thermostats which regulate the flow of respect to a coach installation. All parts of the coach are
the coolant within the cooling system. designated “Left-Hand”,”Right-Hand”, “Front” or “Rear”
Fuel is drawn from the fuel tank through the rear in relation to the normal position of the driver facing
gear-case driven fuel pump, and then through the forward. Engine manufacturer’s designations have
electronic engine control system’s ECM, through the been retained to eliminate potential problems in engine
fuel filter and into the fuel supply and return manifold. It is parts identifications and locations.
then forced into the fuel inlet in the cylinder heads and
finally to the injectors. Excess fuel from the injectors is LUBRICATION
returned to the fuel tank via the manifold and connecting
lines. Since the fuel is constantly circulating through the OIL CHANGE INTERVALS: CATERPILLAR
injectors, it serves to cool the injectors and also carries C-12
off any air in the fuel system. The oil change intervals for engines are greatly
Fresh air is drawn through the air cleaner assembly by dependent on the operating conditions of a particular
the turbocharger which is powered by the engine’s coach (e.g. loads, speed, terrain etc.). The engine oil
exhaust gas. The air then flows through the should be changed every 10,000 miles (16,000 km). Use
Charge-Air-Cooler in the radiator assembly, where it is lubrication specification S-2 (Heavy Duty Engine Oil -
cooled and returned to the intake manifold. The cooled 15W-40) as shown in Section 10 of this manual.
air charge is then introduced into each cylinders with the Coaches equipped with a Caterpillar C-12 engine have
engine’s intake strokes. an oil capacity of 36 U.S. quarts (34.1 liters). Oil is added
Some general specifications of these engine are through the oil fill nozzle on the front gear case. All diesel
shown in the following chart. engines require heavy-duty lubricating oils The only
lubricating oil recommended for Caterpillar C-12 diesel
Engine Specifications engines is the API Service Code CF4 - SAE 15W-40.
Caterpillar C-12 NOTE: Solvents should not be used as flushing oils in
Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 cycle running engines. Dilution of the fresh refill oil supply
Number of Cylinders . . . . . . . . . . . . . . . . . . . . . . 6 can occur, which may be detrimental.
Bore (inches) . . . . . . . . . . . . . . . . . . . . . . . . . 5.12
Bore (mm) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130 LUBRICATING OIL: CATERPILLAR C-12
Stroke (inches) . . . . . . . . . . . . . . . . . . . . . . . . 5.91 The reduction of friction and wear by maintaining an
oil film between moving parts is the primary requisite of a
Stroke (mm) . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
lubricant. Film thickness and its ability to prevent
Compression . . . . . . . . . . . . . . . . . . . . 16.25 to 1 metal-to-metal contact of moving parts is related to oil
Total Displacement (inches) . . . . . . . . . . . . . . 732 viscosity. Basic requirements of such oils are lubricating
Total Displacement (mm) . . . . . . . . . . . . . . . . . 12 quality, high heat resistance and control of
Rated Full Load Speed (RPM) . . . . . . . . . . . 2100 contaminants.
Valve Lash (engine stopped) . . . . . . . . . . . . . . Temperature is the most important factor in
determining the rate at which deterioration or oxidation
Inlet Valve 0.38 ¦ 0.08 mm (.015 ¦ .003 inch) of the lubricating oil will occur. The oil should have
Exhaust Valve0.64 ¦ 0.08 mm (.025 ¦ .003 inch) adequate thermal stability at elevated temperatures,
Compression Brake . . 1.02 ¦ 0.08 mm (.040 ¦ thereby precluding formation of harmful carbonaceous
and/or ash deposits. The piston and compression rings
.003 inch)
must ride on a film of oil to minimize wear and prevent
Maintenance and repair information on the engine will ring seizure. At normal rates of consumption, oil reaches
be found in the engine manufacturer’s service manuals. a temperature zone at the upper part of the piston where
Engine controls, accessories and related components rapid oxidation and carbonization can occur. In addition,
are covered in the applicable sections of the manual. as oil circulates through the engine, it is continuously
Refer to Section 6 (Cooling), 7 (Electrical), 9 (Fuel), and contaminated by soot, acids, and water originating from
10 (Lubrication). combustion.
MCI Parts Books, Maintenance Manuals, Service Oil that is carried up the cylinder liner wall is normally
Bulletins and other technical publications identify all consumed during engine operation. The oil and
engine parts as “Left-Hand”, “Right-Hand”, “Front” or additives leave carbonaceous and/or ash deposits
“Rear” when viewing the engine from the flywheel end. when subject to the elevated temperatures of the

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combustion chamber. The amount of deposits is use of synthetic oil does not permit extension of
influenced by the oil composition, additive content, recommended oil drain intervals.
engine temperature and oil consumption rate.
Policy On Lubricant Additives
Until they are exhausted, detergent and dispersant
MCI does not recommend or support the use of any
additives aid in keeping sludge and varnish from
supplementary lubricant additives. These include all
depositing on engine parts. But such additives in
products marketed as top oils, break-in oils, graphitizers
excessive quantities can result in detrimental ash
and friction reducing compounds.
deposits. If abnormal amounts of insolubles form,
particularly on the piston in the compression ring area, NOTE: MCI warranty applicable to Caterpillar C-12
early engine failure may result. diesel engines provides in part that the provisions of
such warranty shall not apply to any engine unit which
Specification has been subject to misuse, negligence or accident.
Oil quality is the responsibility of the oil supplier. (The Accordingly, malfunctions attributable to neglect or
term “oil supplier” is applicable to the refiners, blenders failure to follow the manufacturer’s fuel or lubricating
and rebranders of petroleum products, and does not recommendations may not be within the coverage of
include distributors of such products.) There are many the warranty.
brands of commercial crankcase oil marketed today.
Obviously, engine manufacturers or users cannot
completely evaluate the numerous commercial oils. The
selection of a suitable lubricant in consultation with a MAINTENANCE
reliable oil supplier, observance of his oil drain
recommendations (based on used oil sample analysis INSPECTION AND TESTS
and experience) and proper filter maintenance, will
provide the best assurance of satisfactory oil Engine
performance. Generally, the service intervals noted in the Caterpillar
API Service Code Military SAE Service Manual are minimum requirements to keep the
Classification Specification Grade engine warranty valid. Engine conditions may vary
CF-4 MIL-L-46167 15W-40 depending on the service environments from one coach
to another, therefore, maintenance schedules should be
SAE 15W-40 grade oil is recommended in the C-12 formulated with the specific coach’s service conditions
diesel engines. The expected ambient temperatures in mind.
and engine operational parameters must be considered A suggested preventive maintenance practice
by the owner-operator when selecting the proper grade includes a regularly scheduled testing of fuel and
of oil. lubricating oils by either the oil supplier or an
Lubricants meeting specification MIL-L-46167 are independent testing laboratory. Since the oil supplier
used in Alaska and other extreme sub-zero locations. knows the physical properties of his products and
Generally they may be described as 5W-20 multigrade maintains laboratories to determine practical oil drain
lubricants made up of synthetic base stock and having intervals, take advantage of this service and request a
low volatility characteristics. Although they have been check of frequently drained oil samples and a report of
used successfully in some severe cold regions, they are the results.
not considered as desirable as SAE 15W-40 with Engine oil cooler flow and oil temperature should be
auxiliary heating. For this reason, they should be checked every 25,000 miles (40,000 km) to determine oil
considered only where engine cranking is a severe cooler efficiency. This check should be made by
problem and auxiliary heating aids are not available on inserting a steel jacketed digital thermometer into the
the engine. dipstick tube immediately after stopping a hot, loaded
engine. If the oil temperature exceeds the coolant
Synthetic Oils temperature by more than 60_F (33_C), the oil cooler
Synthetic oils may be used in Caterpillar engines, may be clogged.
provided they are API licensed and meet the
perfomance and chemical requirements of Mounts
non-synthetic oils. Synthetic oils offer improved low The rubber engine mounts should be inspected every
temperature flow properties and high temperature 24 months or 75,000 to 96,000 miles, whichever comes
oxidation resistance. Product information about first. The isolator’s transmissibility (i.e., the ratio of
synthetic oils should be reviewed carefully. Performance vibration transferred across an isolator) can be quickly
additives often respond differently in synthetic oils. The checked using the following procedure.

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NOTE: After operating the engine for 20-30 minutes

! CAUTION ! shut off and remove the rocker covers. Inspect the
lube oil puddles that normally form where the fuel
connectors join the cylinder head and where the fuel
pipes join the fuel pipe nuts. If there is any leakage at a
When working close to a running engine, stay
connection, disassemble, inspect, and correct or
away from moving belts, be sure all loose
clothing is secured and eye protection is worn. replace the suspect part (connector washer,
connector, injector or any jumper line). Test and
reinspect.
1. Using a mechanic’s stethoscope or equal, place REPLACEMENT: ENGINE COMPONENTS:
one end on the un-isolated side of engine mount (top CATERPILLAR C-12 ENGINE
bracket). Make note of the tone or sound. Engine Oil Filter
2. Next, place the end on the isolated side of engine Engine oil filter should be changed every 10,000 miles
mount (cradle rail). Make note of this tone or sound. (16,000 km) or whenever the crankcase oil is drained
and refilled. The engine oil filter is located along the
If the mount is in good order, two different tonal lower RH side of the engine block.
qualities should be present. A high metallic pitch should 1. Turn battery disconnect switch to “OFF” position.
be present at the un-isolated side, while a lower dull 2. With appropriate filter removal tool, unfasten the
sound should be present on the isolated side. The same screw-on filter element.
tone or pitch on both sides would indicate a
3. Replace with new element and tighten 2/3 turn
non-functioning isolator.
past element gasket contact with base.
4. Start engine and check for leaks.
OPERATIONAL CHECKS Rubber Mounts
NOTE: Mounts should be replaced only as complete
sets (i.e. upper mount and lower snubber).

! CAUTION ! ! CAUTION !
Improper installation of the motor mounts can
Always check the internal fuel distribution contribute to excessive engine vibration. When
system for leaks after injector, jake brake or new mounts are installed, mount bolts should
rocker arm tube replacements, and anytime the be left loose until engine can be run for a short
fuel connections under the rocker cover are period of time. If engine is accelerated a few
suspected of leaking. Failure to correct a times, the rubber mount will find its correct
serious fuel leak in this area, can lead to position and then mount bolts can be torqued
dilution of the lube oil and bearing and/or and cotter keys installed.
cylinder wall damage.

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ELECTRONIC ENGINE CONTROL SYSTEMS

GENERAL DESCRIPTION control functions, refer to the “Caterpillar Electronic
Engine” schematic provided in the “Air & Electrical
Generally speaking most diesel engine electronic Schematics” booklet. Detailed service procedures for
control systems operate approximately in the same the Caterpillar electronic engine control system may be
manner. The systems receive, process and store found in the applicable Caterpillar Troubleshooting
information from sensors located throughout the engine and/or Service Manuals.
and other related components. Input from these and
other devices determines the command signals issued
to maintain the engine’s proper environmental and COMPONENTS
economic operation.
The systems are responsible for the storage and ELECTRONIC CONTROL MODULE (ECM)
retrieval of vital engine information, the processing of The Electronic Control Module (ECM) is the
received data and the transmittal of command signals micro-processor controlled electronic monitoring and
that will achieve correct engine functions relating to storage unit. The ECM unit mounts directly to the lower
operation. The systems can be interconnected to other LH side of engine block (Figure 2). The ECM should
electrically or electronically controlled components such identify problem conditions within the engine by
as transmissions and throttle devices. The following is a comparing input from the various sensors to a set of
list of functions or tasks that a typical engine control parameters (calibration and design data) stored within
system should address. Control of the engine’s fuel the ECM. After processing input data the ECM sends
injection function (i.e., timing of and fuel metering), command pulses to engine components (i.e., injector
including transient fuel control (smoke control). solenoids to initiate fuel injection), or other coach
Communication with the transmission control system. components. The ECM also receives feedback from
Monitoring of rated speed and power, torque shaping, engine components regarding the start and end of
engine governing, cold start logics, engine oil, intake air injection for a given cylinder, or from other coach
and coolant temperatures. components such as WTEC and ABS control modules.

NOTE: Caterpillar system automatically controls

components such as: Jake brake, fast idle, cruise
control, turbo-boost dump and cooling fan, etc...

These systems also have protection circuits that

reduce power and eventually shut down the engine
completely in the event of a potentially damaging engine
condition such as; low oil pressure, low coolant level or
high engine temperature. The systems should
incorporate a self-diagnostic feature, and may identify a
fault condition or potential problem by illuminating
telltale lights. Fault codes identifying failed components
are logged into the system’s ECM memory for later
readout by maintenance personnel. ELECTRONIC CONTROL
G0509
MODULE
The specific systems that are covered by this
sub-section are the Caterpillar electronic engine control
systems. For convenience this write-up will reference
Caterpillar terminology where applicable to describe the
components. In order to better explain the engine G0509 Figure 2. Electronic Control Module (C-12)

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The Caterpillar engine control utilizes the J1587 serial occur in either of the sensor circuits, the engine can be
link source inputs, which are furnished direct from the started and will run with only one sensor.
engine ECM to the transmission ECU, and from the
transmission to other coach components via the vehicle BOOST PRESSURE SENSOR
interface module (VIM). The Caterpillar electronic The Boost Pressure Sensor is an absolute pressure
engine control system is used to control all engine and sensor measuring intake manifold air pressure. Boost
selected coach components functions. The ECM is Pressure as displayed by service tools and
factory programmed and is determined by specific communicated over the data link is the value obtained by
engine, transmission, tire size and axle ratio subtracting the atmospheric pressure (as measured by
combinations. Reprogramming of ECM will be required the Atmospheric Pressure Sensor) from the absolute
for any change from the OEM combination. value measured by the Boost Pressure Sensor for the
C-12 engine. The Boost Pressure Sensor can measures
pressures from 0 kPa (0 psi) up to 472 kPa (68psi). The

! !
sensor is supplied by the ECM with 5 Volts DC.
CAUTION ATMOSPHERIC PRESSURE SENSOR
Read the “WELDING CAUTION” in the The atmospheric pressure sensor is an absolute
introduction of this book before beginning any pressure sensor measuring crankcase pressure. Both
welding procedures on coaches equipped with the boost pressure and oil pressure communicated to
an electronic engine control system. service tools and over the data link is calculated by
subtracting the atmospheric pressure sensor reading.
ELECTRONIC UNIT INJECTORS (EUI): The atmospheric pressure sensor can measure
CATERPILLAR C-12 ENGINE pressures from 0 kPa (0 psi) to 116 kPa (16.8 psi). The
sensor is supplied by the ECM with 5 volts DC.
The Electronic Unit Injectors (EUI) are electronically
controlled solenoid operated fuel injectors mounted into ENGINE OIL PRESSURE SENSOR
the cylinder head above each cylinder. The The oil pressure sensor is an absolute pressure
solenoid-operated poppet valve on each EUI performs sensor measuring oil pressure in the oil gallery. The
injection timing and fuel metering functions. While the difference between the pressure measured by this
EUI’s solenoid valve is de-energized (poppet open), the sensor (oil pressure) and the atmospheric pressure is
fuel enters the injector through two fuel inlet filter the oil pressure as displayed on the service tools and
screens. communicated over the data link. The ECM uses this
At the Beginning Of Injection (BOI), which occurs at a sensor input only if the parameter for engine monitoring
specific degree of crank angle before (TDC) the ECM is programmed to Warning, Derate, or Shutdown. The oil
would request EUI function and energize the solenoid pressure sensor can measure pressure from 0 kPa
valve. When the valve is energized (poppet closed), fuel (0psi) to 1135 kPa (165 psi). The sensor is supplied by
is pressurized and injection is initiated. The duration of the ECM with 5 volts DC.
solenoid valve being closed is referred to as the Pulse
Width (PW), which determines quantity of fuel injected. COOLANT TEMPERATURE SENSOR
Pressurization of fuel inside the injector occurs The coolant temperature is used to control “Cold
mechanically by a conventional cam-operated plunger. Mode” operation and for engine monitoring. The coolant
After the pulse width time has passed, the EUI’s solenoid temperature sensor is a thermistor (passive sensor) not
valve is de-energized, it is re-opened, pressure requiring a supply voltage. Cold mode operation is
decreases and fuel injection ends. activated whenever the coolant temperature is below
64ºF (18ºC). Cold mode remains active until coolant
ENGINE SPEED/TIMING SENSORS temperature exceeds 64ºF (18ºC). In cold mode, engine
The engine speed/timing sensors are used to power is limited and the low idle engine speed may be
determine both engine speed and fuel injection timing. elevated. Cold mode is not disabled if the engine
The camshaft position sensor detects this information monitoring feature is programmed to OFF.
from a gear on the camshaft and the crankshaft position
sensor detects this information from a gear on the THROTTLE POSITION SENSOR (TPS):
crankshaft. Under normal operating conditions the The Throttle Position Sensor (TPS) is the
engine monitors both the camshaft and crankshaft potentiometer assembly which is mounted in the
position sensor while cranking (starting) and the electronic foot pedal assembly (EFPA), located on the
crankshaft position sensor while running. However, the driver’s area floor. It converts the throttle’s relative
design provides for a redundant system. Should a failure position into a signal usable by the ECM (Figure 4).

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COOLANT LEVEL SENSOR (CLS): coolant level drops, the ECM should alert the driver by
CATERPILLAR C-12 illuminating the amber “CHECK ENGINE” and/or the red
The Coolant Level Sensor (CLS) is OEM supplied and “STOP ENGINE” tell-tale warning lamps. The ECM
mounted in the surge tank assembly. The CLS monitors should initiate the engine power-down and/or
the coolant level and sends a constant signal to the ECM shut-down protection sequence.
to indicate coolant level in the engine’s cooling system. If

COOLANT INTAKE MANIFOLD BOOST

TEMPERATURE AIR TEMPERATUREPRESSURE
CAMSHAFT POSITION SENSOR SENSOR
SENSOR OIL PRESSURE SENSOR
SENSOR

COOLANT
TEMPERATURE
SENSOR

FRONT TOP VIEW

LEFT SIDE VIEW

CATERPILLER C12 ENGINE
CRANKSHAFT POSITION
SENSOR

FRONT RIGHT SIDE VIEW

G1313

G0536 Figure 3. Sensor Locations

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INTAKE MANIFOLD AIR TEMPERATURE Engine Protection (With Shutdown Sequence)

SENSOR When the engine protection feature is initiated both
The intake manifold air temperature is used to control the amber “CHECK ENGINE” and red “STOP ENGINE”
the cooling fan output and for engine monitoring. The warning lights on the instrument/gauge panel’s tell-tale
intake manifold air temperature sensor is a thermistor strip are illuminated. A fault code is logged into the
(passive sensor) not requiring a supply voltage. The ECM’s memory and the power reduction sequence is
intake manifold air temperature is used to warn the driver begun.
of an excessive intake manifold air temperature. It will The engine override switch is provided in the driver’s
not cause the ECM to derate or shutdown the engine area. The switch will allow an additional thirty seconds of
when engine monitoring is programmed to derate or fuel before shutdown occurs. The override switch is
shutdown. designed so that it can be held “ON” to continuously
overrule shutdown, however, an override code is logged
into the ECM when the override switch is activated.
If the engine protection feature is triggered, it will
PEDAL TREAD remain active until the fault is cleared, corrected or the
system is reset. The Caterpillar system can be reset by
THROTTLE ASSEMBLY parking the coach, shutting off the ignition, waiting ten
POTENTIEOMETER seconds and then restarting the engine. If the fault was
temporary, the indicator lights on the tell-tale strip cluster
should go out and normal operation should resume, and
a fault code would be logged into memory. The memory
may be cleared by use of the Caterpillar ET. If the fault
remains after the engine is restarted, the problem is not
temporary, and maintenance or repair of the problem is
C0763
indicated.

C0763 Figure 4. Throttle Position Sensor

Coolant Over-Temperature Protection
Coolant Over-Temperature Protection (COP) protects
the engine from excessive coolant over-temperature
conditions by automatically reducing engine power
MAINTENANCE when the coolant temperature exceeds 225 ˚F (107 ˚C)
(Figure 3). The amount of power reduction depends on
DIAGNOSTICS: CATERPILLAR C-12 the position of the TPS at the time of condition, and how
ENGINE much the coolant temperature increases above 225 ˚F
(107 ˚C). If the cause of the over-temperature is
The Caterpillar electronic engine control system’s
temporary, such as climbing a severe grade, the amount
diagnostic features can be separated into three areas:
of available power will be increased as the temperature
Engine Performance Diagnostics, Self-Diagnostics and
decreases, with 100% power available as soon as the
Engine System Protection.
temperature drops to 225 ˚F (107 ˚C).
Engine Performance Diagnostics
The Caterpillar system continuously monitors various
sensors and makes adjustments to injector timing and TROUBLESHOOTING
fuel quantity input, depending on PROM programming Troubleshooting the Caterpillar systems can be
and sensor input, to provide optimum performance and divided into the following two areas. The first being
minimal acceleration smoke under all operating mechanical checks such as wiring and connector
conditions. Cold weather starting is improved by problems. The second being the proper use of a
matching the fuel input and timing to the ambient air Caterpillar Electronic Technician (ET) in interpreting
temperature. logged codes and/or obtaining complete information on
diagnosis of components. The replacement of any
System Self-Diagnostics
internal engine components should be based on
The system continuously monitors itself and all diagnostic codes indicating faulty components.
related wiring for faults. If a fault is detected, the “CHECK
ENGINE” and/or “STOP ENGINE” light(s) should NOTE: Refer to the applicable troubleshooting
illuminate (depending on the severity of the fault). manual and/or the appropriate instruction manual for
the ET being used.

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MECHANICAL CHECKS: CATERPILLAR flashes three more times, this would indicate a fault code
C-12 ENGINE 13, which is interpreted as a problem with the coolant
Mechanical checks involve inspection of all wiring level sensor. Refer to the Caterpillar Troubleshooting
and connectors for proper connection, dirty or corroded Manual for a complete listing of the fault codes and their
terminals and visual inspection of components for loose, meanings.
damaged, or missing parts. All wiring is Teflon coated
with crimp-type connectors. Solder-type connectors are REPLACEMENT: ECM/SENSORS:
not used nor recommended on wiring because normal CATERPILLAR C-12
vibration will cause the solder connection to fail in time. Electronic Control Module
1. Turn main battery disconnect switch to “OFF”.
ELECTRONIC TECHNICIAN: CATERPILLAR
C-12 ENGINE 2. Disconnect the harnesses from ECM.
The Caterpillar electronic service tools for the 3. Unfasten and remove the mounting fasteners
electronic control system are designed to help the retaining ECM to engine block.
service technician analyze faults or problems within the 4. Reinstall service replacement ECM in reverse
system. The Caterpillar electronic service tools are order of removal steps.
required to perform some sensor calibrations
electronically. The Caterpillar electronic service tools are Turbo-Boost & Timing Reference Sensors
required to change engine parameters. The Caterpillar 1. Turn main battery disconnect switch to “OFF”.
Electronic Technician requires a personal computer with 2. Disconnect the harnesses from sensor.
the ET software. Cat ET also requires a Caterpillar 3. Unfasten and remove the fastener(s) and sensor
Communication Adapter. from manifold or gearcase.
MANUAL FAULT CODE RECALL: 4. Reinstall replacement sensor in reverse order of
CATERPILLAR C-12 removal steps.
If a Caterpillar ET system is not immediately available, Threaded Sensors
the fault codes logged in the ECM’s memory can be 1. Turn main battery disconnect switch to “OFF”.
manually flashed by use of the override switch on the LH
switch panel. When the switch is actuated, the “Stop 2. Disconnect the harnesses from sensor.
Engine” tell-tale lamp should begin flashing (if codes are 3. Unfasten and remove the sensor from engine
present). The tell-tale should flash a sequence of codes block, manifold or surge tank.
which identify the faulty component or system. For 4. Reinstall replacement sensor in reverse order of
example, if the light flashes once, then pauses and removal steps.

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DIAGNOSTIC CODES
C-12 DIAGNOSTIC CODES

FIRST SECOND CODE CAUSE

FLASH FLASH
0 0 0052-11 Air Inlet Shutoff Shutdown
0084-14 Quick Stop Occurrence
0171-03 Outside Air Temperature Sensor Open Circuit
0171-04 Outside Air Temperature Sensor Short Circuit
0171-11 No Ambient Air Temperature Data
0224-11 Theft Deterrent Active
0224-14 Engine Cranking with theft Deterrent Active
0246-11 Brake Switch #1
0247-11 Brake Switch # 2
0 1 0071-00 Idle Shutdown Override
1 2 0111-02 Coolant Level Sensor Fault
1 3 0174-03 Fuel Temperature Sensor Open Circuit
0174-04 fuel Temperature Sensor Short Circuit
1 4 0121-05 Retarder Solenoid Low/High Open Circuit
0121-06 Retarder solenoid Low/High Short Circuit
0122-05 Retarder solenoid Med/High Open Circuit
0122-06 Retarder Solenoid Med/High Short Circuit
2 1 0041-03 8 Volt Supply Above Normal (Accelerator Pedal)
0041-04 8 Volt Supply Below Normal (accelerator Pedal)
0232-03 5 Volt Supply Above Normal (Engine Pressure Sensor)
0232-04 5 Volt Supply Below Normal (Engine Pressure Sensor)
2 4 0100-03 Oil Pressure Sensor Open Circuit
0100-04 Oil Pressure Sensor Short Circuit
2 5 0102-00 Boost Pressure Reading Stuck High
0102-03 Boost Pressure Sensor Open Circuit
0102-04 Boost Pressure Sensor Short Circuit
2 6 0108-03 Atmospheric Pressure Sensor Open Circuit
0108-04 Atmospheric Pressure Sensor Short Circuit
2 7 0110-03 Coolant Temperature Sensor Open Circuit
0110-04 Coolant Temperature Sensor Short Circuit
2 8 0091-13 Throttle Sensor Calibration
2 9 0030-13 Invalid PTO Throttle Signal
0030-13 PTO Throttle Sensor Calibration
3 1 0084-1 Loss of Vehicle Speed Signal
3 2 0091-08 Invalid Throttle Signal

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3 4 0064-12 Loss of Engine Cam Sensor RPM Signal

0190-12 Loss of Engine Crank Sensor RPM Signal
3 5 0190-00 Engine Overspeed Warning
3 6 0084-02 Invalid Vehicle Speed Signal
0084-08 Vehicle Speed Out of Range
0084-10 Vehicle Speed Rate of Change
3 8 0105-03 Inlet Manifold Temperature Sensor Open Circuit
0105-04 Inlet Manifold Temperature Sensor Short Circuit
4 1 0084-00 Vehicle Overspeed Warning
4 2 0022-11 Camshaft Sensor to Crank Sensor Calibration
0022-13 Check Timing Sensor Calibration
4 6 0100-01 Low Oil Pressure Warning
0100-11 Very Low Oil Pressure
4 7 0071-01 Idle Shutdown Occurrence
0071-14 PTO Shutdown Timer Occurrence
5 1 0168-02 Intermittent Battery
5 5 N/A No diagnostic Code Detected
5 6 0253-02 Check Customer or System Parameters
0253-11 Check Transmission Customer Parameters
5 8 0231-11 J1939 Data Link Fault
0249-11 J1922 Data Link Fault
5 9 0252-11 Incorrect Engine Software
6 1 0110-00 High Coolant Temperature Warning
0110-11 Very High Coolant Temperature
6 2 0111-01 Low Coolant Level
0111-11 Very Low Coolant Level
6 4 0105-00 High Inlet Manifold Temperature
0105-11 Very High Inlet Manifold Temperature
6 5 0174-00 High Fuel Temperature Warning
6 6 0054-05 Output # 6 Open Circuit
0054-06 Output # 6 Short Circuit
6 7 0055-05 Output #7 Open Circuit
0055-06 Output # 7 short Circuit
6 8 0191-07 Transmission Not Responding
7 1 0043-02 Ignition Key Switch Fault
7 2 0001-11 Cylinder 1 Fault
0002-11 Cylinder 2 Fault
7 3 0003-11 Cylinder 3 Fault
0004-11 Cylinder 4 Fault

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7 4 0005-11 Cylinder 5 Fault

0006-11 Cylinder 6 Fault

TORQUE SPECIFICATIONS
(FOR COMPLETE ENGINE SPECIFICATIONS REFER TO THE APPROPRIATE DETROIT DIESEL ENGINE
SERVICE MANUAL)

Front Motor Mount Bolts (Rear of Coach) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 ft-lbs (102 NSm)

Rear Motor Mount Bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195 ft-lbs (260 NSm)
Rear Motor Mount Cradle Bracket Locknuts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 ft-lbs (150 NSm)
Crankshaft Vibration Damper Bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134-155 ft-lbs (182-210 NSm)
Crankshaft Pulley Bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134-155 ft-lbs (182-210 NSm)
Oil Drain Plug . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 ¦ 11 ft-lbs (70 ¦ 15 NSm)

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SECTION 8B

COLD WEATHER STARTING

GENERAL The heater is supplied with a 3/16-inch HPN cord and
plug set. A junction box is supplied. This box is mounted
The following devices will help improve cold weather on the secondary lavatory tank, and is accessible
starting by warming key components. through the rear service door.
These heaters are non-serviceable, except for the
ENGINE HEATERS cords, and if faulty, the heaters must be replaced.

BLOCK HEATER AUXILIARY HEATERS

An immersion engine block heater is standard. It is a The auxiliary heater can preheat the engine coolant to
115-volt, 1500-watt, single loop element type, fitted in aid in cold weather starting. See Section 16B for full
the block behind the crankcase dipstick. details on maintenance and operation.

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SECTION 8C

JACOBS ENGINE BRAKE SYSTEM

For all maintenance information on the Jacobs Engine Brake System for the Series 60 engine, refer to the Detroit Diesel
Series 60 Service Manual (SECTION 1 ENGINE) and for the Caterpillar C-12 engine, refer to the Caterpillar Service
Manual.

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 Date March 2003

SECTION 9
FUEL SYSTEM

A -- Fuel System
B -- Accelerator Pedal
C -- Air Cleaner - Dry Type
D -- Cruise Control

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SECTION 9A

FUEL SYSTEM
CONTENTS OF THIS SECTION

SUBJECT PAGE
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9A-3
Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9A-3
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9A-3
Fueling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9A-3
Diesel Fuel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9A-4
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9A-7
Fuel System Priming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9A-7
Fuel Flow Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9A-7
Fuel Pro 382 Fuel Filter (Optional) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9A-9
Fuel Tank Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9A-10
Fuel Filter (Strainer) Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9A-10
Dry Break System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9A-12
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9A-14
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9A-14

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CHECK VALVE

FIGURE 1. Fuel System

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GENERAL DESCRIPTION NOTE: The filling nozzle is not supplied with the
coach. Service and maintenance information on the
The coach fuel system is a closed loop, continuous nozzle can be obtained from the vendor.
flow system. The coach has a 222 U.S. gallon (840 litre)
at 95% capacity fuel tank. An auxiliary fuel tank is OPERATION
optional. Fuel filling is performed at either the RH or LH The engine fuel pump draws fuel from the tank
side of coach through the fuel filler door. Two different located towards the center of the coach. Fuel flows
types of filler necks (Standard and Dry Break) are through the fuel filter/strainer into the pump and out to
available on the fuel tank. the engine injectors. The fuel then flows through the
The optional Emco Wheaton “Posi-Loc 105” dry break metering device controlled by the engine electronic ECU
fueling system provides for safe and efficient fueling of and out into the fuel manifold to each cylinder’s injector.
the coach. The system allows for unattended fueling Constant pressure from the fuel pump and a restrictor at
without worry of fuel spills through special coupling the return fitting of the fuel manifold assures that all
devices mounted on the fuel tank and on the fuel island injectors are filled. Fuel flows out of the restrictor device
nozzle. This filler neck is designed to assure a leak-free and to the return tube of the fuel tank.
connection and a “dry-break” disconnect. The fueling FUELING
nozzle is designed to connect and lock into the filler neck
adapter. It automatically stops fuel flow by sensing the
back pressure created during filling and triggering the CAUTION
shut off mechanism.
Do not fill the tank from both necks at once,
COMPONENTS or even have both fill caps open simulta-
neously. This would bypass the level con-
Fuel System trol operation, and could result in filling be-
yond 95% tank capacity (in violation of Fed-
The fuel system consists of a fuel tank with standard
eral regulations) and cause a potential
filler nozzle and whistle device, fuel lines, filter, strainer, overflow.
pump, fuel manifolds (integral in cylinder heads), fuel
pipes (inlet and outlet), auxiliary heater check valve, and The standard fuel tank has the basic filler nozzle
injectors (Figure 1). For further information on the basic assembly with the open-style nozzle filler neck. When
engine fuel system components, consult the the fuel fill nozzle is inserted into the filler neck, fueling
appropriate Detroit Diesel Engine Service Manual. can begin. When the tank is approximately 95% full the
whistle feature should signal that fueling is done.
Dry Break System
The fuel nozzle of the dry break system is inserted into
the filler neck adapter and rotated clockwise 30 degrees
Filler Neck Assembly to the locked position. Fueling may begin when the
The system has a filler neck assembly mounted on operator opens the poppet lever of the fuel nozzle, and
the fuel tank. The inlet neck assembly incorporates a 3 pulls and latches the trigger mechanism, allowing fuel to
p.s.i. pressure relief valve, basic overflow level control flow through the nozzle (Figure 2).
valve with whistle, and filler neck adapter assembly with With the nozzle open, fuel enters the tank at 20 to 50
poppet valve adapter and dust cap. GPM. As the tank fills, displaced air activates the whistle.
When the tank is 95% full, the level control valve closes
Fueling Nozzle and the slight back pressure of 1.1 to 1.5 p.s.i. causes
The system consists of a fueling nozzle assembly the fuel nozzle trigger to trip and stop fuel flow.
located at the fuel island. The nozzle assembly The fueling nozzle’s poppet lever can now be rotated
incorporates a manually operated poppet actuation up to allow the nozzle to be disconnected from the filler
lever, fueling trigger with notch latching device and neck adapter. The pressure relief valve equalizes the
adapter locking lugs. tank pressure. Replace the dust cap onto the filler neck.

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NOTE: The cloud point should be 10oF (6oC) below

the lowest expected fuel temperature to prevent wax
crystals from clogging the fuel filters. If prolonged
idling periods or cold weather conditions below
+32oF (0oC) occur, lighter distillate fuels may be more
practical. The same consideration must be made
when operating at altitudes above 5,000 feet (1524
metres).

The Fuel Oil Selection Chart

The Fuel Oil Selection Chart will also guide users in
choosing the proper fuel for various applications. The
FIGURE 2. Engaging the Nozzle fuels used must be clean, completely distilled, stable,
and noncorrosive. Distillation range, cetane number,
sulfur content, and cloud point are four of the most
important fuel properties that must be controlled for
DIESEL FUEL satisfactory engine operation. Engine speed load and
ambient temperature all influence diesel fuel selection
The quality of fuel oil used for high-speed diesel
with respect to distillation range and cetane number.
engine operation is a very important factor in obtaining
satisfactory engine performance, long engine life, and Cold Weather Considerations
acceptable exhaust emission levels. During cold weather engine operation, the cloud
Detroit Diesel designs, develops and manufactures point (temperature at which wax crystals begin to form in
commercial diesel engines to operate on diesel fuels diesel fuel) should be 10_F (6_C) below the lowest
classified by the ASTM as Designation D-975 (grades expected fuel temperature to prevent wax crystals from
1-D and 2-D). These grades are very similar to grades clogging the fuel filters.
DF-1, DF-2 of Federal Specifications VV-F-800. A reputable fuel oil supplier is the only one who can
assure you that the fuel you receive meets the distillation
end point, cetane number, sulfur content, and cloud
“Burner” Fuels point property limits shown in the Fuel Oil Selection
Burner fuel (furnace oils or domestic heating fuels) Chart. The responsibility for clean fuel that meets Detroit
generally require an open flame for satisfactory Diesel-Allison specifications lies with the fuel supplier as
combustion. The ignition quality (cetane rating) of well as the operator.
burner fuel (ASTM D-396) is poor compared to diesel At temperatures below 32_F (0_C) pay particular
fuels (ASTM D-975). attention to cold weather starting aids for efficient engine
In some regions fuel suppliers may distribute one fluid starting and operation.
that is marketed as either diesel fuel (ASTM D-975) or Numerous fuels meeting the properties shown in the
domestic heating fuel (ASTM D-396), sometimes Fuel Oil Selection Chart may be used in the Detroit Diesel
identified as burner, furnace or residential fuel. Under engines. Alternate fuels (some with sulfur and/or cetane
these circumstances, investigate the fuel to determine if limits) that have been used in Detroit Diesel engines are
the properties conform with those indicated in the Fuel No. 1 and No. 2 diesel fuels, kerosene, aviation turbine
Oil Selection Chart (Figure 3). (jet) fuels, and burner fuels.
Final
General Fuel Boiling Cetane Sulfur Cloud
Application Classification Point Number Content Point

All Applications Winter No. 1-D 675_F 45 0.50 SEE

357_C
Summer No. 2-D 675_F 40 0.50 NOTES
357_C

FIGURE 3. Fuel Oil Selection Chart

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Distillation Requirement Diesel Fuel Additives

The fuel chosen should be completely distilled Very small amounts of isopropyl alcohol
material: it should show at least 98% by volume recovery (isopropanol) may be used to preclude fuel line
when it is subjected to ASTM D-86 distillation. Fuels freeze-up in winter. No more than one pint of isopropyl
marketed to meet Federal Specification VV-F-800 alcohol should be added to 125 gallons of diesel fuel for
(grades DF-1 and DF-2) and ASTM Designation D-975 adequate protection.
(grades 1-D and 2-D) meet the completely-distilled
criteria. The following chart shows the differences in
properties of VV-F-800 and ASTM D-975 fuels (Figure 4).
WARNING
Never add commercially-marketed die-
Fuel Contamination sohol, gasohol or gasoline to diesel fuel.
Fuel oil should be clean and free of contamination. An explosion and fire hazard will exist if
Inspect storage tanks and stored fuel regularly for dirt, these blends are mixed or burned.
water or water-emulsion sludge, and clean them if they
are contaminated. Storage instability of fuel can lead to MCI does not recommend or support using any
varnish or sludge forming in the tank. The presence of supplementary fuel additives. These include all products
these contaminants from storage instability must be marketed as fuel conditioners, smoke suppressants,
resolved with the fuel supplier. masking agents, deodorants, and tune-up compounds.

ASTM VV-F-800, DF-2 ASTM

Specification or VV-F-800 D-975 North D-975
Classification Grade DF-1 1-D America Other 2-D
Flash Point, min. 38_C 38_C 52_C 56_C 52_C
100_F 100_F 125_F 133_F 125_F
Carbon residue (10%) 0.15 0.15 0.35 0.20 0.35
residuum), mass % max.
Water & Sediment, % — 0.05 — — 0.05
by vol. max.
Ash, % by wt. max. 0.01 0.01 0.01 0.02 0.01
Distillation Temperature, — — — — 282_C
90% by vol. recovery, 540_F
min. 288_C 288_C 338_C 357_C 338_C
550_F 550_F 640_F 675_F 640_F
max. 330_C — 370_C 370_C —
End Point max. 626_F 698_F 698_F
Viscosity
Kinematic, cSt, min. @ 40_C 1.3 1.3 1.9 1.8 @ 20_C 1.9
Saybolt, SUS, min. @ 100_F — — — — 32.6
Kinematic, cSt, max. @40_C 2.9 2.4 4.1 9.5 @ 20_C 4.1
Saybolt, SUS, max. @ 100_F — 34.4 — 40.1

Sulfur, mass % max. 0.50 0.50 0.50 0.70 0.50

Cetane No. min. 45 40 45 45 40
FIGURE 4. Federal Specifications and ASTM Diesel Fuel Properties

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Combustion chamber temperature depends on

CAUTION ambient temperature, engine speed, and load. Poor
vaporization is more apt to occur during severely cold
weather, prolonged engine idling and light load
MCI does not recommend using drained lu- operation. Therefore, engines will show better
bricating oil in diesel fuel. Furthermore, De- performance operating under these conditions when
troit Diesel will not be responsible for any lower distillation end point fuels are used. Consult the
detrimental effects which it determines re- Fuel Oil Selection Chart (Figure 3).
sulted from this practice.
Ignition Quality (Cetane Number)
There is a delay between the time the fuel is injected
NOTE: Detroit Diesel recommends using No. 2-D into the cylinder and the time that ignition occurs. The
diesel fuel in all normal applications; however, No. 1-D length of this delay is expressed in terms of cetane
is acceptable. number (rating). Rapidly ignited fuels have high cetane
numbers (50 or above). Slowly ignited fuels have low
cetane numbers (40 or below). The lower the ambient
Fuel Sulfur temperature, the greater the need for a high cetane fuel
The fuel sulfur content should be as low as possible to that will ignite rapidly.
avoid premature wear, excessive deposit formation, and Difficult starting may be experienced if the fuel’s
to minimize the sulfur dioxide exhausted into the cetane number is too low. Furthermore, engine knock
atmosphere. Limited amounts can be tolerated, but the and puffs of white smoke may be experienced during
amount of sulfur in the fuel and engine operating engine warm-up, especially in severely cold weather
conditions can influence corrosion and deposit when operating with a low cetane fuel. If this condition is
formation. allowed to continue for a prolonged time, harmful
All diesel fuels contain a certain amount of sulfur. Too deposits will accumulate in the combustion chamber.
high a sulfur content results in excessive cylinder wear. Consult the Fuel Oil Selection Chart (Figure 4).
For most satisfactory engine life, use fuels containing
less than 0.5% sulfur. The detrimental effect of burning Proposed ASTM D-975, Grade 3-D
high-sulfur fuel is reflected in Detroit Diesel lube oil MCI does not recommend using proposed grade 3-D
change interval recommendations. Detroit Diesel diesel fuel in any of its engines. This grade of fuel was
recommends monitoring the Total Base Number proposed, but not accepted by the ASTM.
(TBN-ASTM D-664) of the lube oil frequently and that the The grade 3-D which was proposed is undesirable in
oil drain interval possibly be reduced. Consult the Fuel that it possesses poor ignition quality (i.e. lower cetane);
Oil Selection Chart. allows greater sulfur content (up to 0.7% by weight);
allows the formation of more carbon deposits
Distillation End Point (Conradson carbon residue); and allows the blending of
Fuel can be burned in an engine only after it has been heavier, more viscous boiling point fractions that are
vaporized. The temperature at which fuel is completely difficult to burn. The latter tend to increase combustion
vaporized is described as the distillation end point chamber deposits. This type of fuel usually manifests
(ASTM D-86). The distillation (boiling) range of diesel poor cold weather properties (wax formation
fuels should be low enough to permit complete tendencies). In addition, the poor ignition quality
vaporization at combustion chamber temperatures. adversely affects noise and emission levels.

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MAINTENANCE NOTE: It may be necessary to remove a valve rocker

cover and loosen a fuel pipe nut to bleed any trapped
air from the fuel system. Ensure that the fuel pipe is
FUEL SYSTEM PRIMING retightened before installing the rocker cover.

Restarting an engine after it has run out of fuel can be

difficult. After fuel is exhausted from the tank, it is FUEL FLOW CHECK
pumped from the primary filter until the fuel supply is too Check fuel flow by disconnecting the flexible fuel
low to sustain engine firing. The primary filter must be return line from the fitting at the rear bulkhead. Place the
free of air for the system to provide adequate fuel for the end of the return line in a convenient receptacle. As fuel
injectors. must pass through the return line restriction fitting, do
not disconnect the line at the bracket on top of the
When the engine runs out of fuel, the following
engine.
procedures must be performed before restarting.
1. For turbocharged engines, start and run the engine
1. Fill the fuel tank by adding a minimum of 20 gallons at 1800 RPM. A fuel flow of 1.4 gallons (5.3 liters) per
(76 liters) of fuel. minute is specified with a fuel line restriction fitting
2. Actuate the priming pump (at the rear junction box) having a 0.070-inch (1.78 mm) spill orifice.
for several minutes. 2. Dip the end of the return line into the fuel container.
Air bubbles rising to the surface indicate that air is
NOTE: If the entire system is to be purged of air as being drawn into the fuel system on the suction side
well, allow fuel to flow freely from the fuel return line of the fuel pump. If air is present, tighten all fuel line
until a solid stream without air bubbles is observed. connections between fuel tank and fuel pump.
If fuel flow is too low for satisfactory engine
performance, check for faulty fuel lines, clogged filters
3. Start the engine and check for leaks. or a malfunctioning fuel pump.

ENGINE BULKHEAD

S60 FUEL HOSE

SECONDARY FUEL FILTER

FUEL SUPPLY HOSE

PRIMARY FILTER

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1. Hose Assy 14. Fitting

2. Clamp 15. Capscrew

3. Fitting 16. Fitting

4. Shut-off Valve 17. Fuel Pro Harness

5. Fitting 18. Trim Lock

6. Fitting 19. Bracket

7. Vacuum Switch 20. Hose Assy

8. Bushing 21. Locknut

9. Nut 22. Fuel Pro Filter

10. Clamp 23. Fitting

11. Hose Assy 24. Bushing

12. Fitting 25. Fitting

13. Bushing 26. Capscrew

27. Drain Hose

FIGURE 5. DDC Fuel Pro 382 Filter

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 Date March 2003 Page 9A-9

FUEL PRO 382 FUEL FILTER (OPTIONAL) Fuel Pro Fuel Filter Removal
To reduce maintenance costs, MCI offers the optional NOTE: Have a new replacement filter element on
installation of the Fuel Pro 382 Fuel Filter (Figure 5 & 6). hand and ready to install. This procedure requires
This new single fuel filter replaces the existing primary draining the fuel from the filter body. Fuel will continue
and secondary fuel filters and will also provide longer to slowly drain from the fuel tank if it is full. A quick filter
filter service life through accurate lifespan control by element change should eliminate the need for fuel
scanning the fuel level in the filter cap. priming and will minimize the loss of fuel.
When new, the fuel level in the filter will be very low and 1. Switch main battery disconnect OFF.
the filter is causing minimal restriction. As the filter 2. Position a clean drain pan under the filter drain
ages, contamination collects on the filter element from cock. Pan capacity should be at least 3 gallons.
the bottom up. In the contaminated area the restriction 3. Open vent cap and drain valve to drain fuel into a
increases and the fuel level in the filter rises indicating suitable container until fuel level is below the collar.
the remaining filter life. When the fuel level reaches the Close the drain valve.
top of the filter cartridge, the element should be 4. Remove the collar by turning counter-clockwise.
replaced at the next scheduled maintenance interval. Remove cover and seal. Discard seal.
5. Remove the old filter and dispose of it in an
environmentally responsible manner, according to
state and/or federal (EPA) recommendations. Be
sure the old filter center grommet has been
removed. Clean the area around the filter mounting
stud.
Fuel Pro Fuel Filter Installation
1. Install the new filter. Be sure that the filter grommet is
seated.
2. Check condition of filter spring (inside clear cover).
Reinstall cover with new seal and hand tighten
collar. Use collar wrench to tighten collar an
additional two ribs distance.
3. Remove the vent cap from the top of the clear cover.
Replace the seal.
4. Fill the Fuel Pro with fuel until it covers the filter.
Replace the vent cap and tighten by hand. Do not
overtighten.
5. Start the engine. When oil pressure reaches normal
operating level, increase engine RPM to fast idle for
one full minute to purge any air from the fuel system.
6. If the engine fails to start, see Fuel System Priming.
FIGURE 6. DDC Fuel Pro 382 Filter
7. With engine idling, carefully open the vent cap
enough to let air into the cover. When the fuel level
lowers about half way on the filter, close the vent
cap again. (Do not overtighten the cap.) Over a few
hours of operation, the fuel level will drop close to
the bottom of the filter. This is normal and, as the
filter clogs, the fuel level will rise to visually indicate
filter life and condition.

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FUEL TANK REMOVAL (FIGURE 8) FUEL FILTER (STRAINER) REPLACEMENT

A welded aluminum fuel tank is mounted between the The filter removes debris which may be in the fuel
rear axle and the battery compartment. Fueling is before it passes into the fuel pump, and removes the fine
performed through a spring return door in the body particles of solid matter that have passed through the
panel. Provisions are made in the body paneling for primary filter, preventing such material from entering the
access to the fuel tank, should removal be necessary. engine injectors.
1. Drain the fuel tank completely before removal. Every 10,000 miles (16,000 km), change the fuel
(Either siphon or pump from the fuel fill tube or filters, and open the drain at the bottom of the fuel tank to
remove the fuel sender unit and use a pump with a drain off any water or sediment.
flexible hose or use the drain plug located on the
bottom of the tank.) NOTE: The service interval at which the strainer and
2. Remove the the fuel door on the right hand side of filter should be changed is determined by operating
the coach. conditions and the cleanness of the fuel used.
3. Loosen the clamps (Item 3) on both fuel necks, and 1. Turn battery disconnect switch to OFF.
slide the rubber hose (Item 2) off the tank spigot.
2. Before removing the fuel filter or strainer, close the
4. Disconnect the fuel supply and return lines from the
shut-off cock which is installed at the primary filter
fuel tank fittings.
inlet port (Figure 5).
5. Disconnect the fuel primer pump supply and return
lines (Item 7, 8). NOTE: Valves are installed to prevent fuel from
6. Disconnect the vent lines from the fuel fill syphoning out of the tank while the filters are being
necks.(Items 5, 6). serviced. An optional shut-off cock also prevents the
7. Disconnect the electrical connector from the fuel fuel pump from emptying and losing its prime.
level sensor (Item 1).
3. Remove the filter by turning it counterclockwise.
8. Lift the fuel tank over the frame member and slide it
Replace it with a new filter and tighten it 2/3 of a turn
out of the compartment.
after it contacts the gasket. Use new gaskets with
each replacement.
CAUTION 4. Return all valves to the open position, restart the
engine and check for any leakage.
Take care when moving the tank past wiring
harnesses.

9. Turn the front of the tank toward the road side of the
coach to complete the removal.
Reinstall the tank in the reverse order of removal.
Torque the nuts (Item 4) to 30 ft-lbs (40 N-m) dry.

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FUEL TANK INSTALLED

FUEL FILL ASSEMBLY

FUEL TANK

CHECK VALVE

FUEL FILLER NECK ASSEMBLY

FIGURE 7

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DRY BREAK SYSTEM Whistle

The whistle screws into the outlet of the control valve
Level Control Valve (Figure 9). If the whistle is not functioning properly,
Proper functioning of the level control valve (Figure 8) refueling operations could be hindered. Inspect the
is critical. Malfunctions can cause the system to underfill whistle regularly for obstructions or cracks in the
or overfill. On a regular basis, visually inspect the valve housing. Clean any obstruction from the unit as
for cracks in the housing, leaks around the flange required. If the body is cracked, replace the whole unit.
gasket, or obstructions in the body housing. Remove
To replace the whistle, simply unscrew the faulty
any obstructions and replace the gaskets as necessary. whistle and replace it with a new one. Hand tightening is
If the housing is cracked, replace the unit. When
all that is necessary. Do not overtighten it.
replacing the valve, also install a new gasket. When
installing a new gasket, it must be located so that the
bleed valve is in the center of the slot. MALE REED ASSEMBLY
1 1/4” NPT
MALE 1” NPT

BODY HOUSING
1” NPT

WHISTLE BODY
BODY RETAINER 2351

FIGURE 9. Fuel Filling Monitor Whistle

VALVE BODY Pressure Relief Valve
The pressure relief valve relieves any excess pressure
in the fuel tank over 3 psi. This eliminates any chance of a
tank rupturing, making preventive maintenance highly
important (Figure 10).
Frequently inspect the pressure relief valve for any
cracks in the housing, leaks around the flange gasket, or
obstructions. Remove any obstructions, and replace
leaking gaskets. Do not attempt to repair a
2350 malfunctioning pressure relief valve; replace it.

FIGURE 8. Level Control Valve

BODY HOUSING

1 1/4” NPT
OUTLET

GASKET POPPET (ASSEMBLY)

2352

FIGURE 10. Pressure Relief Valve

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Filler Neck Adapter 4. Install a new tetraseal.

The adapter (Figure 11) assures a leak-free 5. Install a new poppet.
connection and a dry-break disconnect. 6. Reassemble in reverse order of disassembly.
Routinely inspect the adapter for a secure flange seal When not refueling, the aluminum dust cap protects the
and tighten or replace it as necessary. If a leak around adapter (Figure 12). An O-ring seals the adapter
the poppet is evident, see the repair procedures below. opening. Replace the entire dust cap if cracks are
Replace the poppet if it is chipped or cracked. detected, or if the bayonet studs are broken or bent.
Inspect the dust cap O-ring for nicks or cuts; replace a
damaged or worn O-ring.
POPPET GUIDE
GASKET ADAPTER BODY

TETRASEAL CABLE

POPPET

RETAINER RING SPRING 2353

FIGURE 11. Filler Neck Adapter DUST CAP (J1201-- 004)

O-- RING
(563650)
No special tools are necessary. To replace the flange
gasket, simply unbolt the adapter from the filler neck,
replace the gasket, and secure the bolts. To replace the
poppet or tetraseal: BAYONET STUD
1. Unbolt the adapter.
2354
2. Remove the retainer ring.
3. Remove the poppet assembly. FIGURE 12. Filler Neck Adapter Dust Cap

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 Date March 2003 Page 9A-14

TROUBLESHOOTING
Problem Possible Cause
Nozzle will not shut off. 1. Flow below minimum rate of 20 GPM.
2. Float valve stem bent.
3. Float missing or not fastened by a cotter pin.
4. Adapter flange bolts loose.
5. Nozzle malfunction. Return it to the factory for a rebuilt exchange nozzle.
6. Float valve disc damaged. Remove the float valve assembly, invert and
pour fuel on the valve disc. Fuel should slowly leak through. Replace the
float with a new float if it is defective.
Fuel oil blowback when nozzle is 1. Operator has pulled disconnect handle and rotated nozzle off adapter
disconnected. before tank has vented.
2. Lock pin bent. Operator tried to remove nozzle without pulling
disconnect handle.
3. No pressure equalization hole in tank portion of filler neck.
4. Roll over ball check not level.
5. Tank has been topped off and filler neck is full of fuel under pressure.

SPECIFICATIONS
FUEL TANK & FILLER NOZZLE ASSEMBLY
Capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222 U.S. gals. (840 liters)
FUEL FILTERS
Dual Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Davco
Optional Single Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fuel Pro 382

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SECTION 9B

ACCELERATOR PEDAL

CONTENTS OF THIS SECTION

SUBJECT PAGE
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9B-3
Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9B-3
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9B-3
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9B-3
Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9B-3
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9B-3
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9B-3

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 Date March 2003 Page 9B-2

PEDAL TREAD

THROTTLE POSITION SENSOR

ASSEMBLY
BRAKE PEDAL ASSY

HARNESS

MOUNTING PLATE

BRAKE VALVE ASSY

FIGURE 1. Electronic Accelerator Pedal

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 Date March 2003 Page 9B-3

GENERAL DESCRIPTION MAINTENANCE

The coaches use an electronic accelerator pedal The TPS (throttle position sensor) mechanism is
assembly. The accelerator pedal’s electronic throttle is sealed and does not require any lubrication. The pedal
an integral part of the engine electronic control system, assembly and the area around the throttle’s roller
and referred to as a throttle position sensor (TPS). The mechanism should be kept clean of dirt and other
accelerator pedal assembly is mounted onto the brake foreign matter. Inspect the pedal assembly every 50,000
pedal assembly’s mounting plate (Figure 1). miles (80,000 km) for excessive wear or damage.

COMPONENTS
The accelerator pedal consists of an electronic
CAUTION
throttle assembly with mounting and a MCI foot pedal
MCI recommends replacing the throttle as
with rubber tread. The pedal assembly is secured to the
an assembly. The throttle’s potentiometer
brake pedal mounting plate with machine screws. The and the spring roller actuator are service-
throttle incorporates a spring returned roller actuator able items; however, pedal calibration may
mechanism, a throttle position sensor (potentiometer) be required after repairs have been made.
and interconnecting harness with floor plate.

OPERATION
As the pedal is pressed down, the throttle’s roller and
REMOVAL
actuator lever rotate the potentiometer. The 1. Place the battery disconnect switch to OFF.
potentiometer’s relative position determines the signal 2. Disconnect the pedal harness from the
which is transmitted to the ECM, which interprets the interconnecting harness.
signal and either increases or decreases engine RPM. 3. Unfasten the pedal mounting screws and remove
them from the brake pedal mounting plate.
NOTE: Because of the different signal requirements 4. Remove the foot pedal rubber tread. Unfasten the
for specific ECMs, different engine installations will pedal mounting screws from the throttle pedal.
require specific throttle position sensor assemblies.
Some throttle assemblies will include an idle INSTALLATION
validation sensor and additional harness. 1. Reinstall in the reverse order of Removal.

SPECIFICATIONS

FOOT PEDAL
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MCI

MOTOR COACH INDUSTRIES

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 Date March 2003 Page 9C-1

SECTION 9C

AIR CLEANER - DRY TYPE

CONTENTS OF THIS SECTION

General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9C-1

Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9C-2
Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9C-2
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9C-2

GENERAL DESCRIPTION Engine air enters the air cleaner through intake ducts
The coaches are equipped with a single dry-type and all foreign matter, dust and dirt is prevented from
replaceable element air cleaner, located in the engine entering the engine by the filter element. The dirt
compartment at the rear of the coach at eye level. See particles will collect in the element assembly. Any
Figure 1. Access to the air cleaner is through the engine moisture collected in the assembly will drain out through
compartment door. the bottom of the water trap above the air cleaner.
A resettable restriction indicator is installed near the
air cleaner to inform the operator of the filter condition.
The indicator is connected to the outlet side of the air
cleaner. It measures air flow restriction in inches of water.
NOTE: Do not over-service the unit: there is no need
for visual inspection of the element. Replace the
element only when the indicator is in the red zone.

Figure 1. Air Cleaner Assembly

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 Date March 2003 Page 9C-2

MAINTENANCE system each time the engine oil is changed. It is not

necessary to disassemble the air cleaner for inspection.
SERVICE 4. Check the air cleaner body for cracks, loose nuts
When the indicator service window reaches the red and bolts.
zone, replace the filter element and reset the indicator. 5. Check the clamps on the air induction system to
See Figure 2. determine if they are loose, broken or missing.
6. Replace, repair, or correct any improper situations.
AIR RESTRICTION INDICA-
TOR
7. Inspect the gasket sealing surface inside the air
cleaner. It must be smooth, flat and clean.
8. Install the air cleaner element. Be certain the
element seals securely.
9. Inspect the element cover gasket and replace it if
necessary.

INSTALLATION
Whenever it becomes necessary to remove the air
cleaner assembly (dry type) take care when reinstalling
the air cleaner.

CAUTION
A. Never operate the vehicle without an ele-
Figure 2. Restriction Indicator ment in the air filter assembly.
By monitoring the restriction indicator, maximum filter B. Use only original equipment filter elements.
element service can be achieved. The indicator also
C. Whenever the element has been removed
provides protection to the engine and helps maintain
from the filter body, clean the inside of the filter
fuel system efficiency. body with a clean, damp cloth.
To service the air cleaner:
D. Do not ignore the warning given by the air
1. Stop the engine.
restriction indicator. To do so is to invite serious
2. Loosen the wingnut securing the air cleaner engine damage.
element to the air cleaner.
E. Store new elements in a protected area free
3. Remove the element. from dust and damage.
NOTE: Remove any dust from the interior of the air F. Use the proper element when replacing the
cleaner body with a damp cloth before reinstalling a filter element.
clean element.
G. Do not wash or reuse dirty elements.
Proper inspection prolongs engine and air cleaner
service life. Inspect the air cleaner and air induction

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 9D-1

SECTION 9D

CRUISE CONTROL
CONTENTS OF THIS SECTION

SUBJECT PAGE
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9D-3
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9D-3
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9D-4
Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9D-4
System Road Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9D-4
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9D-5

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 Date March 2003 Page 9D-2

1
2

ON/OFF RES
ACCEL

CANCEL SET
COAST

3 4
1. CRUISE CONTROL ON/OFF
2. RESUME/ACCELERATE
3. CRUISE CONTROL CANCEL
4. SET/COAST

FIGURE 1. Cruise System Controls

FIGURE 2. Cruise System Controls

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 Date March 2003 Page 9D-3

GENERAL DESCRIPTION 2. Press the accelerator pedal until you reach the
Cruise control is a driver-controlled, automatic speed desired speed, then press and release SET/COAST
control system designed for highway vehicles. switch.
NOTE: When driving with cruise control in use, the
WARNING speed may be increased for passing, etc., without
cancelling the set speed: press the accelerator in the
usual manner. Releasing the accelerator pedal
Do not use cruise control in heavy traffic or returns the vehicle to the set speed.
when road surfaces are slippery or loose. Decreasing Set Speed
Cruise control is a completely electrical system; all Vehicle speed setting may be decreased by one of
functions are performed through the engine’s Electronic two methods:
1. Press and hold the SET/COAST switch until
Control Module (ECM). (The electrical schematic for the
reaching the desired speed. Releasing the SET
DDEC in Section 7 has detailed electrical information.)
switch will set the new speed.
The cruise control uses coach speed for setting cruise
control. This allows the system to control maximum 2. Lightly press the brake to disengage the system.
coach speed while the cruise control is operating. The Allow the vehicle to coast to the desired speed, then
cruise control operates with “zero droop,” allowing press and release the SET switch.
accelerator override at any time. With cruise control in use, the transmission may be
The system controls are mounted on the steering shifted in the normal way without manually disengaging
the cruise control system. The system will automatically
wheel (Figures 1 and 2). Cruise control can be turned
adjust the engine RPM, allowing the shift to be
on at any time, but coach speed must be approximately
completed and it will maintain the set speed at the new
28 mph (45 kph) or greater before speed can be set. gear selection.
(This minimum speed may vary due to rear-end ratio.)
Canceling the Set Speed
OPERATION The cruise control automatic operation may be
canceled by:
Turning the System On 1. Press the CANCEL button.
Press the ON/ OFF switch to turn system ON.
2. Make a slight brake application.
Setting Vehicle Speed 3. The vehicle speed drops below 28 mph (45 km/h).
1. Set the vehicle speed by accelerating to the desired
speed. NOTE: Pressing CANCEL or brake activation will
cancel cruise control but leaves the system enabled
2. Press and release the SET/COAST switch, then
for resume.
release accelerator pedal.
The green “cruise enabled” telltale on the left-hand
cluster will stay on until the cruise control is turned off. NOTE: RESUME features may be used again when
automatic operation is cancelled with steps 2 or 3.
NOTE: The Cruise Control System will not accept The RESUME feature will automatically return the
speed settings, nor will the RESUME feature operate
vehicle speed to the setting it had before cancellation
below approximately 28 mph (45 km/h).
and maintain the set speed.
Increasing Set Speed
Increase the vehicle speed setting by one of two When the cruise control automatic operation is
methods: canceled, any objectionable vehicle motion can be
1. Press and hold the RES/ACCEL switch until minimized by depressing accelerator lightly before
reaching the desired speed. Releasing the ACCEL disengaging cruise control. Using the CANCEL button
switch will set the new speed. instead of the brake will result in a smoother transition.

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 Date March 2003 Page 9D-4

MAINTENANCE 1. With a coach speed of 40 mph (64 kph) turn the

system on.
INSPECTION (DDEC) 2. Activate the Set switch to establish a speed setting
Every three months, 25,000 miles (40,000 km) or 900 greater than 28 mph (45 kph). Maintain the coach
operating hours: speed within one mph of the speed setting.
1. Visually inspect the system wiring and connectors 3. Apply the brake and allow coach to coast down to
for deterioration or wear. less than 28 mph (45 kph). Depress and release the
Resume switch. The original coach speed should
2. Perform the system operation road test. not be resumed.
SYSTEM ROAD TEST 4. Accelerate coach to 30 mph (48 kph) and activate
When the cruise control system or any of its features the Resume switch; the coach should automatically
accelerate to its original set speed.
are not used regularly, the operational check and road
test should be performed monthly. If the road test 5. Press and hold in the Resume switch. The coach
indicates the system is not operating properly, do not speed should increase at approximately 1 mph per
use the system until it has been repaired, tested and second. Release the Resume switch at 50 mph (80
proven to be operating properly. kph). This should establish a new set speed of 50
mph (80 kph).
Select a road where traffic and weather conditions will
safely permit performing the road test. 6. Press and hold the Set switch and allow coach to
coast down to 40 mph (64 kph). Release the switch.
This should establish a new set speed of 40 mph
WARNING (64 kph).
NOTE: The minimum speed at which the cruise
Do not use cruise control on wet or slip- control will function is approximately 28 mph (45 kph).
pery roads. However, this will vary slightly due to axle ratio, tire
size, etc.

Figure 3. ECU Harness Connector

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 Date March 2003 Page 9D-5

TROUBLESHOOTING
CRUISE CONTROL SWITCHES
NOTE: All basic mechanical checks and physical inspections must be performed with DDR with no problem found
and you have now been referred here.

58-1 Determine Check to see that this is a DDEC Yes Go to 58-4.

Type of Cruise cruise control system.
Control System
If it is a DDEC cruise control sys- No. Go to 58-2
tem, do you know if it is either a
vehicle speed or engine speed
system?
58-2 Check if Cal- Turn ignition on. Display reads: N/A You have an engine speed cruise
ibration is Set Up MPH CRUISE. control system. Go to 58-4.
for DDEC Cruise
Plug DDR into the 12 pin DDL
Control
connector.
Select PROM ID (MODE 03) for Display reads: ## You have a vehicle speed cruise
display. MPH CRUISE control system. Go to 58-4.
(where ## = a
number).
Look through data being dis-
played until MPH CRUISE is
found.
58-3 Check ECM Disconnect the vehicle harness Terminals and con- Replace ECM. Then go to 58-30.
Connectors connector at the ECM. nectors are okay.
Check terminals at the ECM ve- Problem found. Repair terminals/connectors.
hicle harness connector (both the Then go to 58-30.
ECM and harness side) for dam-
age, corrosion and unseated pins
or sockets.
58-4 Checking
Out Cruise Con-
trol Switches &
Wiring*

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 Date March 2003 Page 9D-6

To speed up the check-out of cruise control switches, Quick-check tables have been developed. These tests are all to
be run with the ignition on but the engine not running. Also, a DDR must be plugged into the 12 pin, DDL connector. Go
through all three Quick-Check Tables (Tables l to lll) to completely check out the cruise control switches and wiring.

Example
Taking Table I, step 2 you would do the following:
1. Ignition on, engine off, DDR plugged in.
2. Turn the Cruise Control On/Off switch to “On”.
3. Select “CRUISE SWITCHES” (Mode 23) on DDR for display.
4. Note the DDR display. If, for example, it shows “??”, you would proceed to Table II. If instead it shows “OFF”,
proceed to step 58-6.
5. Whenever you are directed to the fault trees, you are always asked to recreate the same conditions which led you
there. In this example that would mean to turn the Cruise On/Off switch to “On” before taking any readings.

CRUISE CONTROL QUICK-CHECK TABLES

Table l
Check-Out of On/Off Switch & Wiring (Ignition “On”, Engine Not Running)

On/Off DDR Readout If you get

Switch SET RESUME Being DDR this display,
Step Status Switch Switch Looked At Display Okay? then go to:
1 OFF OFF OFF CR ON/OFF SW OFF Yes Table I, Step 2
ON No 58-5
?? No Table ll
2 ON OFF OFF CR ON/OFF SW OFF No 58-6
ON Yes Table ll
?? No Table ll

*If the parking brake is wired into the cruise system, block the wheels and turn off the parking brakes before beginning
these tests.

Table ll
Check-Out of Brake and Clutch Switches & Wiring (Ignition ”On”, Engine Not Running)*

On/Off Clutch DDR Readout If you get

Switch Brake Pedal Being DDR this display,
Step Status Pedal (if any) Looked At Display Okay? then go to:
1 ON OFF OFF BRAKE/CLT SW OFF Yes Table II, Step 2
ON No 58-7*
OPEN No 58-8
SHRT No 58-9
2 ON OFF ON BRAKE/CLT SW OFF No 58-10
(if no ON Yes Table ll, Step 3
clutch, OPEN No 58-11
skip to SHRT No 58-12
Step 3)
3 ON ON OFF BRAKE/CLT SW OFF No 58-13
ON Yes Table III
OPEN No 58-14
SHRT No 58-15

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 Date March 2003 Page 9D-7

Table lll
Check Out of SET and RESUME Switches & Wiring

On/Off DDR Readout If you get

Switch SET RESUME Being DDR this display,
Step Status Switch Switch Looked At Display Okay? then go to:
1 ON OFF OFF SET/COAST SW OFF Yes Table III, Step 2
ON No 58-16
OPEN No 58-17
SHRT No 58-18
2 ON ON OFF SET/COAST SW OFF No 58-19
ON Yes Table III, Step 3
OPEN No 58-20
SHRT No 58-21
3 ON OFF OFF RES/ACCEL SW OFF Yes Table III, Step 4
ON No 58-22
OPEN No 58-23
SHRT No 58-24
4 ON OFF ON RES/ACCEL SW OFF No 58-25
ON Yes 58-26
OPEN No 58-27
SHRT No 58-28

*If the parking brake is wired into the cruise system, block the wheels and turn off the parking brakes before beginning
these tests.

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Printed in Canada.
 Date March 2003 Page 9D-8

58-7 Check for Turn ignition off. Less than or equal Either the brake or clutch switch
Shorted or Mis- to 10,000 ohms. is miswired or faulty. Rewire or re-
wired Brake place switch. Then go to 58-30.
S itch
Switch
Disconnect the vehicle harness
connector at the ECM.
Turn ON the Cruise On/Off switch.
Read resistance between socket Greater than Go to 58.3.
J2 on the vehicle harness connec- 10,000 ohms or
tor and a good ground. open.
58-8 Check for Turn ignition off. Greater than 5 Either the brake or clutch switch
Open at the On/ ohms or open. is open or miswired, or an open
Off Ckt exists in ckt #543 or ckt #558.
Repair open or replace switch.
Then go to 58-30.
Disconnect the vehicle harness
connector at the ECM.
Turn ON the cruise On/Off switch.
Read resistance between socket Less than or equal Go to 58-3.
G2 on the vehicle harness con- to 5 ohms.
nector and a good battery
ground.
58-9 Check for a Turn the ignition off. Less than or equal Either the brake or clutch switch
Short at the to 10,000 ohms on is shorted or a short to ground ex-
Brake/Clutch On either reading. ists in ckt #531. Repair short or
Ckt replace switch. Go to 58-30.
Disconnect the vehicle harness
connecter at the ECM.
Turn ON the cruise On/Off switch.
Read resistance between socket
J2 on the vehicle harness connec-
tor and a good ground.
Also read resistance between Greater than Go to 58-3.
socket J2 and a good ground. 10,000 ohms or
open on both read-
ings.

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 Date March 2003 Page 9D-9

58-10 Check for Turn the ignition off. Less than or equal Check if bad mechanical contact
Bad Contact or to 10,000 ohms. between the clutch switch and the
Switch Off Ckt clutch. If okay, the clutch switch is
bad. Repair bad contact or re-
place clutch switch. Then go to
58-30.
Disconnect the vehicle harness
connector at the ECM.
Turn ON the cruise On/Off switch.
Apply a weight (brick or other) to
the clutch or have someone else
press and hold the clutch pedal to
the floor.
Read resistance between socket Greater than Go to 58-3.
G2 on the vehicle harness con- 10,000 ohms or
nector and a good ground. open.
58-11 Check for Turn the ignition off. Less than or equal Go to 58-3.
Open at the to 5 ohms.
Brake/Clutch Off
Disconnect the vehicle harness
Ckt
connector at the ECM.
Turn On the cruise On/Off switch. Greater than 5 Either the clutch switch or brake
ohms or open. switch or ckt #531 is open. Re-
pair open or replace switch. Then
go to 58-30.
Apply a weight (brick or other) to
the clutch or have someone else
press and hold the clutch pedal to
the floor.
Read resistance between socket
J2 on the vehicle harness connec-
tor and a good ground.
58-12 Check for Turn ignition off. Less than or equal Either the clutch switch is shorted
Short at the Brake to 10,000 ohms on or a short to ground exists in ckt
Off/Clutch Circuit either reading. #543. Repair short or replace
switch. Then go to 58-30.
Disconnect the vehicle harness
connector at the ECM.
Turn ON the cruise On/Off switch.
Apply a weight (brick or other) to Greater than Go to 58-3.
the clutch or have someone else 10,000 ohms or
press and hold the clutch pedal to open on both read-
the floor. ings.
Read resistance between socket
G2 on the vehicle harness con-
nector and a good ground.

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 Date March 2003 Page 9D-10

58-13 Check for Turn ignition off. Less than or equal Determine brake switch opera-
Bad Contact at to 5 ohms. tion:
the Brake Switch
Disconnect the vehicle harness Air Operated
connector at the ECM. Be sure brake switch is mounted
in brake air supply circuit, and
that no kinks or air leads exist.
Not equipped with
manual transmis-
sion.
Turn ON the cruise On/Off switch. Mechanical
Check switch actuator for correct
alignment and/or sticking.
Apply a weight (brick or other) to Test switch operation. Make re-
the clutch or have someone else pairs or replace switch.
press and hold the clutch pedal to
the floor.
Read resistance between socket When repairs are complete, go to
G2 on the vehicle harness con- 58-30.
nector and a good ground.
Greater than 5 Go to 58-3.
ohms or open.
58-14 Check for Turn ignition off. Less than or equal Go to 58-3.
Open at the to 5 ohms.
Brake/Clutch Cir-
Cir
Disconnect the vehicle harness
cuit
connector at the ECM.
Turn ON the cruise On/Off switch. Greater than 5 Either the brake switch or ckt
ohms or open. #531 is open. Repair open or re-
place switch. Then go to 58-30.
Apply a weight (brick or other) to
the clutch or have someone else
press and hold the brake pedal to
the floor.
Read resistance between socket
J2 on the vehicle harness connec-
tor and a good ground.

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 Date March 2003 Page 9D-11

58-15 Check for Turn ignition off. Less than or equal Either the brake switch is shorted
Short at the to 10,000 ohms on or ckt #543 is shorted to ground.
Brake/Clutch Off either reading. Repair short or replace switch.
Ckt Then go to 58-30.
Disconnect the vehicle harness
connector at the ECM.
Not equipped with
manual transmis-
sion.
Turn ON the cruise On/Off switch.
Apply a weight (brick or other) to Greater than Go to 58-3.
the clutch or have someone else 10,000 ohms or
press and hold the brake pedal to open on both read-
the floor. ings.
Read resistance between socket
G2 on the vehicle harness con-
nector and a good ground.
58-16 Check for Turn ignition off. Less than or equal Set switch is shorted or miswired.
Shorted or Mis- to 10,000 ohms. Rewire or replace switch. Then go
wired Set Switch to 58-30.
Disconnect the vehicle harness
connector at the ECM.
Turn ON the cruise On/Off switch.
Read resistance between socket Greater than Go to 58-3.
J1 on the vehicle harness connec- 10,000 ohms or
tor and a good ground. open.
58-17 Check for Turn ignition off. Greater than 5 Either the set switch is open or an
Open at the Set/ ohms or open. open exists in ckt #542. Repair
Coast Off Circuit open or replace switch. Then go
to 58-30.
Disconnect the vehicle harness
connector at the ECM.
Turn ON the cruise On/Off switch.
Read resistance between socket Less than or equal Go to 58-3.
F1 on the vehicle harness con- to 5 ohms.
nector and a good ground.
58-18 Check for Turn ignition off. Less than or equal Either the set switch is shorted or
Short at the Set/ to 10,000 ohms on a short to ground exists in ckt
Coast On Circuit either reading. #541. Repair short or replace
switch. Then go to 58-30.
Disconnect the vehicle harness
connector at the ECM.
Turn ON the cruise On/Off switch.
Read resistance between socket Greater than Go to 58-3.
J1 on the vehicle harness connec- 10,000 ohms or
tor and a good ground. open on both read-
ings.

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 Date March 2003 Page 9D-12

58-19 Check for Turn ignition off. Less than or equal Set switch is miswired or faulty.
Faulty or Mis- to 10,000 ohms. Rewire or replace switch. Then go
wired Set Switch to 58-30.
Disconnect the vehicle harness
connector at the ECM.
Turn ON the cruise On/Off switch.
Find a means to press and hold Greater than Go to 58-3.
the set switch. 10,000 ohms or
open.
Read resistance between socket
F1 on the vehicle harness con-
nector and a good ground.
58-20 Check for Turn ignition off. Greater than 5 Either the set switch is open or
Bad Contact or ohms or open. not making a good contact, or an
Open at the Set/ open exists in ckt #541. Repair
Coast On Circuit open or replace switch. Then go
to 58-30.
Disconnect the vehicle harness
connector at the ECM.
Turn ON the cruise On/Off switch.
Find a means to press and hold
the set switch.
Read resistance between socket Less than or equal Go to 58-3.
J1 on the vehicle harness connec- to 5 ohms.
tor and a good ground.
58-21 Check for Turn ignition off. Less than or equal Either the set switch is shorted or
Short at the Set/ to 10,000 ohms on miswired or a short to the ground
Coast Off Circuit either reading. exists in ckt #542. Repair short or
replace switch. Then go to 58-30.
Disconnect the vehicle harness
connector at the ECM.
Turn ON the cruise On/Off switch.
Find a means to press and hold
the set switch.
Read resistance between sockets Greater than Go to 58-3.
F1 on the vehicle harness con- 10,000 ohms or
nector and a good ground. open on both read-
ings.
Also read resistance between
socket F1 and a good ground.

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Printed in Canada.
 Date March 2003 Page 9D-13

58-22 Check for Turn ignition off. Less than or equal Resume switch is shorted or mis-
Shorted or Mis- to 10,000 ohms. wired. Rewire or replace switch.
wired Resume Then go to 58-30.
S itch
Switch
Disconnect the vehicle harness
connector at the ECM.
Turn ON the cruise On/Off switch.
Read resistance between sockets Greater than Go to 58-3.
G3 on the vehicle harness con- 10,000 ohms or
nector and a good ground. open.
58-23 Check for Turn ignition off. Greater than 5 Either the resume switch is open
Open at the Re- ohms or open. or an open exists in ckt #544.
sume/Accel Off Switch may be miswired. Repair
Circuit open or replace switch. Then go
to 58-30.
Disconnect the vehicle harness
connector at the ECM.
Turn ON the cruise On/Off switch.
Read resistance between socket Less than or equal Go to 58-3.
F2 on the vehicle harness con- to 5 ohms.
nector and a good ground.
58-24 Check for Turn ignition off. Less than or equal Either the resume switch is
Short at the Re- to 10,000 ohms on shorted or a short to the ground
sume/Accel On either reading. exists in ckt #545. Repair short or
Circuit replace switch Then go to 58-30.
Disconnect the vehicle harness
connector at the ECM.
Turn ON the cruise On/Off switch.
Read resistance between socket Greater than Go to 58-3.
G3 on the vehicle harness con- 10,000 ohms or
nector and a good ground. open on both read-
ings.
58-25 Check for Turn ignition off. Greater than 5 Resume switch is miswired or
Faulty or Mis- ohms or open. faulty. Rewire or replace switch.
wired Resume Then go to 58-30.
S itch
Switch
Disconnect the vehicle harness
connector at the ECM.
Turn ON the cruise On/Off switch.
Find a means to press and hold Less than or equal Go to 58-3.
the resume switch. to 5 ohms.
Read resistance between socket
G3 on the vehicle harness con-
nector and a good ground.

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Printed in Canada.
 Date March 2003 Page 9D-14

58-26 Verify Prob- If you were originally referred to “Check Engine” The problem is no longer present.
lem Still Exists set 58-5 (from Quick Check), re- light never comes Go to C1-2, page 35. Go to
turn to the “what to do next” col- on. START-1, page 17, if any other
umn of that step. problems are present.
Otherwise, you have completed “Check Engine” Go to 58-4 and retrace through
the switch check-out process light comes on at the Quick Check.
without detecting a fault. some point.
Clear codes.
Keep the cruise On/Off switch on.
Press and hold the set/coast and
resume/accel switches separately
for at least two seconds each wile
observing the “Check Engine”
light.
Then press and hold the brake
and clutch separately for at least
two seconds each while observ-
ing the “Check Engine” light.
58-27 Check for Turn ignition off. Greater than 5 Either the resume switch is open
Bad Contact or ohms or open. or not making good contact, or an
Open at the Re- open exists in the ckt #545. Re-
sume/Accel Cir- pair open or replace switch. Then
cuit go to 58-30.
Disconnect the vehicle harness
connector at the ECM.
Turn ON the cruise On/Off switch.
Find a means to press and hold
the resume switch.
Read resistance between socket Less than or equal Go to 58-3.
G3 on the vehicle harness con- to 5 ohms.
nector and a good ground.
58-28 Check for Turn ignition off. Less than or equal Either the resume switch is
Short at the Re- to 10,000 ohms. shorted or a short to ground ex-
sume/Accel Off ists in ckt #544. Repair short or
Circuit replace switch. Then go to 58-30.
Disconnect the vehicle harness
connector at the ECM.
Turn ON the cruise On/Off switch.
Find a means to press and hold
the resume switch.
Read resistance between socket Greater than Go to 58-3.
F2 on the vehicle harness con- 10,000 ohms or
nector and a good ground. open.

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Printed in Canada.
 Date March 2003 Page 9D-15

Verify Repairs Turn ignition off. Code 25 (no Repairs are complete.
codes).
Reconnect all connectors.
Turn ignition on. Code 58 (and any All system diagnostics are com-
other codes). plete. Please review this section
from the start to find the error.
Clear codes.
Turn on the cruise On/Off switch.
Press and hold the set/coast and Any other codes Go to START-1, page 17, to ser-
resume/accel switches separately except Code 58. vice other codes.
for at least two seconds each.
Then press and hold the brake
and clutch separately for at least
two seconds each.
Read historical codes.

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 6(59,&( %8//(7,16
6HUYLFH %XOOHWLQV ZLOO EH LVVXHG IURP WLPH WR WLPH WR DFTXDLQW XVHUV ZLWK WKH ODWHVW VHUYLFH SURFHGXUHV 7KH
QXPEHU GDWH DQG WLWOH RI EXOOHWLQV SHUWDLQLQJ WR WKLV VHFWLRQ VKRXOG EH QRWHG EHORZ DV VRRQ DV UHFHLYHG
%XOOHWLQV VKRXOG WKHQ EH ILOHG IRU IXWXUH UHIHUHQFH

1XPEHU 'DWH 6XEMHFW

 Date March 2003

SECTION 10
LUBRICATION

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 Date March 2003 Page 10-1

SECTION 10

LUBRICATION
CONTENTS OF THIS SECTION

SUBJECT PAGE
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-2
Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-2
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-4
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-18

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Printed in Canada.
 Date March 2003 Page 10-2

GENERAL DESCRIPTION Hoses

The coach lube oil hoses are constructed of either
This section will discuss the specific lubrication
elastomer tube with inner steel braiding or Teflon lined
requirements for most coach components. Several
outer stainless braided. Performance of the engine and
different schedules are provided in this section for
auxiliary equipment is greatly dependent on the flexible
reference; however, the intervals specified may not be
hoses’ ability to transfer lubricating oils. Therefore, hose
appropriate for all applications. The “Lubrication
maintenance is an important step to ensure efficient,
Schedule” is provided as a minimum requirements
economical and safe operation of the engine and related
guide for most lubricated components. A location key
equipment. Inspect the hoses for abrading and wear
chart gives the approximate location of service points.
points, and replace any hoses found with these
Where cleaning, removal or disassembly are required
conditions.
for lubrication purposes, procedures will be found in the
applicable sections of this maintenance manual. Power Steering Reservoir
A “Preventive Maintenance Schedule” is also The power steering fluid reservoir has a cartridge filter
included at the end of this section. It includes most and an inlet strainer. A dipstick and a sight gauge
lubrication, cleaning and inspection intervals required facilitate checking the oil level (Figure 1). The reservoir
for coach components. is located at the top front on the Series 60 installations.
Check high lube maintenance items such as engine Add fluid to the reservoir through its fill tube.
crankcase oil, transmission fluid, and other components
shown in the “Inspection Schedule” daily or before the
start of each run. Add oil as needed to bring the level to
the “Full” mark on the dipstick.

COMPONENTS
Fill Tubes
Engine crankcase oil is introduced into the engine
through the oil fill tube location on the right-hand side of
the engine front casing or the front gear case on the
Series 60, engine installation. The power steering
reservoir fill is located on the reservoir, or at the upper RH
side of the engine.
NOTE: Transmission lube oils are introduced through
dipstick tubes or side fill plugs on the transmission Figure 1. Power Steering Reservoir
body.
Filters
Dipsticks The coach engine installations use a two element oil
The dipstick is used to assure proper lube levels in the filtration system. An optional bypass filter arrangement
engine and transmission oil pans. The dipstick may also be added to allow emergency capacity. Most
assembly is located at the upper left-hand side of Series filters are of the screw-on type, and some cartridge types
60 installations. Automatic transmission dipsticks are are also used. Several other different types of filtration
inside the engine compartment door. arrangements and elements are used to remove
contaminants from the coach system’s lubrication oils.
NOTE: B500R transmission installations have an
electronic fluid level monitoring system; however, NOTE: Install a new oil filter element each time a
checking oil levels with the manual dipstick system’s oil is changed. Sometimes no filter is used
inspection method is recommended periodically. (i.e., wheel bearings and trailing axle bearing boxes).

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Printed in Canada.
 Date March 2003 Page 10-3

LUBRICATING OILS & GREASE 1. Remove the breather and fill plug (Figure 2).
Heavy-Duty Engine Oil
Series 60 engines use SAE 15W-40 grade heavy- duty
engine oil exclusively. Engine operation requires
heavy-duty lubricating oils with specialized additives for
diesel engines. These oils provide better lubrication,
have more heat resistance and counteract sludge
formation more effectively than mineral type oils.
Multi-Purpose Gear Oil
The axles use full synthetic gear oils or hypoid gear
oils with extended drain intervals. The viscosities can be
adjusted for temperature ranges in which the coach is
operated. Generally an SAE 75W-140 to 75W-90 grade
oil is suitable. The oil-lubricated wheel bearing on the
front and tag axle can use either multi-purpose or Figure 2. Gear box breather and fill plug
synthetic gear oils.
Automatic Transmission Fluid
Automatic transmissions use lube oils that qualify 2. Fill the gear box with lubricant (Mobilube 75W90 oil)
under torque fluids specification C-4 (i.e., Dexron IIIE or until the lubricant comes out the oil level plug hole.
Dexron III). Coaches with the Allison extended warranty 3. Clean the thread on removed plugs and plug holes
are required to use TranSynd automatic transmission with a degreaser.
fluid. See Section 13. The power steering system uses 4. Install the plugs securely in the gear case.
Dexron automatic transmission fluid.
5. After the first 100 hours of operation, drain out the
Fan Gear Box Oil initial oil, flush out the gear case with an approved
Lubricate the fan gear box before service: non-flammable, non-toxic solvent and refill it.

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 Date March 2003 Page 10-4

MAINTENANCE reduce life. Hoses with wire braid reinforcement are

subject to oxidation and subsequent loss of strength.
MCI recommends a thorough inspection of all hoses
HOSES
at least every 500 operating hours or annually. Look for
Inspection cover damage or indications of damaged, twisted, worn,
Check hoses daily as part of the pre-start up crimped, brittle, cracked or leaking lines. MCI
inspection. Examine hoses for leaks, and check all recommends replacing all hoses during major
fittings, clamps, and ties carefully. Ensure that hoses do overhauls and after a maximum of five years’ service.
not rest on or touch shafts, couplings, heated surfaces, Replacement hose assemblies should be equal to or
sharp edges, or other hazardous areas. Tighten or better than the original equipment.
replace fittings, clamps, ties and hoses as necessary. NOTE: Hoses that have the outer cover worn through
Investigate leaks immediately and take corrective or damaged metal reinforcement should be
action as required. Leaks are potentially detrimental to considered unfit for service.
operation and cause added expense.
Review the plumbing and fasten hoses only after the
engine or related machinery is installed. Extra fasteners
WARNING or readjustment of support may be required during the
life of a unit. Ensure that hoses are routed and clipped to
prevent damage from vibration, abrasion, heat and
Personal injury/property damage may result mechanical loads. Hoses routed close to heated
from fire due to the flammable fluid leakage. surfaces may have a shortened service life. Shields or
protective sleeves may extend hose life in special
applications. Consult with the hose manufacturer
Service Life relative to alternate hose compositions where shields
A hose has a limited service life, determined by the and sleeves are impractical.
temperature, pressure of the gas/fluid within it, age, Hose installation, routing and fitting torque criteria
mounting, amount of flexing and vibration. Road salt can can be obtained from hose suppliers/ manufacturers.

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Printed in Canada.
 Date March 2003 Page 10-5

SERVICE INTERVALS gear oil. The axle has magnets installed in the axle
housing to collect metallic particles, and unitized Teflon
OIL-LUBRICATED COMPONENTS wheel seals. This package provides improved
Service periods for lube oils depend upon several lubrication while extending drain intervals to 250,000
different factors. The service intervals may be gradually miles (400,000 km). If the owner chooses to use
increased or decreased until the most practical oil petroleum-based gear oil, the oil change interval is
change period for a particular service has been 100,000 miles (160,000 km).
established, (based on recommendations from an oil
There is no requirement for initial drain following a
supplier’s analysis of drained oil or from prolonged
break-in period.
experience with a specific lubrication product).
Engine Crankcase Oil Wheel Bearings (Oil-Lubed)
An engine’s oil change intervals greatly depends on Inspect he wheel bearing lube oil and adjust the
the operating conditions of the particular coach (e.g. lubricant level daily. Drain and refill the lube oil every
loads, speed, terrain etc.). Change the engine oil every 100,000 miles (160,900 km) or 3000 operating hours
10,000 miles (16,000 km). and when servicing the hub or wheel bearings.

NOTE: Do not use solvents as flushing oils in running Fan Drive

engines. Dilution of the fresh refill oil supply can occur, The fan drive U-joints are factory-filled, and do not
which may be harmful. need lubricating. The slip joint, has a grease nipple.

Check the engine oil cooler flow and oil temperature Power Steering System
every 25,000 miles (40,000 km) to determine oil cooler Inspect the power steering system’s fluid level and fill
efficiency. Do this check by inserting a steel jacketed it daily. Drain and refill the system with fluid whenever the
thermometer in the dipstick opening immediately after reservoir’s filter is serviced. At 225,000 miles, service the
stopping a hot, loaded engine. If the oil temperature filter and clean the inlet strainer.
exceeds the coolant temperature by more than 60_F NOTE: Dexron III ATF is the only approved fluid for
(33_C), the oil cooler may be clogged.
the power steering system.
Automatic Transmission
ALLISON B500 / 500R GREASE-LUBRICATED COMPONENTS
The automatic transmission is supplied with a “factory Front Axle
filled” lube oil which should be drained and refilled after Grease the front axle knuckle pins and tie rod end
the initial break-in period of 5,000 miles (8,000 km). Later assemblies after the first 4,000 miles (6,500 km), and
oil change intervals should take place every 25,000 every 50,000 miles (80,000 km) afterwards.
miles (40,000 km) or 750 operating hours.
If the coach is under the Allison extended warranty Trailing (Tag) Axle
and uses TranSynd transmission fluid, the initial fluid Lubricate self-steering trailing axle knuckle pins and
changes should be done at 50,000 miles (80,000 km) tie rod end assemblies after the first 4,000 miles (6,500
and 100,000 miles (160,000 km). Later fluid change km), and every 50,000 miles (80,000 km) thereafter.
intervals should take place every 100,000 miles (160,000
km.)
Driveshaft
The driveshaft u-joint bearings and slip-joint require
NOTE: Automatic transmissions with output retarder lubrication every 10,000 miles (16,000 km) with
installations may require more frequent oil changes. multi-purpose grease (code S-17).

Brake Assemblies
ZF ASTRONIC Automatic Shift (Optional)
Inspect and lube slack adjusters every 5,000 miles
The transmission is factory filled with gear oil meeting
(8,000 km) or 150 hours. Reduce interval to 4,000 miles
viscosity specifications listed in the ZF lubricant list
(6,400 km) for severe service.
TE-ML 02, Lubricant Class 02L. Oil change intervals and
temperature specifications are also listed here. A/C Compressor
Drive Axle The air conditioning compressor’s pivot mounting
The drive axle is equipped with Rockwell’s Advanced requires lubrication every 5,000 miles (8,000 km) or 150
Lubrication package, which is designed to use synthetic hours of operation.

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 Date March 2003 Page 10-6

FILTER REPLACEMENT If the coach is under the Allison extended warranty

and uses TranSynd automatic transmission fluid, the
Engine Crankcase Oil Filters filter should be changed after the initial 5,000 miles
Change engine oil filters every 10,000 miles (16,000 (8,000 km), 25,000 miles (40,000 km) and 50,000 miles
km) or whenever the crankcase oil is drained and (80,000 km). Afterwards, filter changes should take
refilled. The engine oil filters are located along the lower place every 50,000 miles (80,000 km).
RH side of the engine block. 1. Turn the battery disconnect switch to OFF.
1. Turn the battery disconnect switch to OFF. 2. Remove the drain plug from the control module
2. With the appropriate filter removal tool, unfasten the sump, and allow it to drain completely.
screw-on filter elements.
3. Insert the new elements and tighten them 2/3 turn NOTE: It is not necessary to drain fluid if only filters
past the element’s contact with the base. are to be changed.
4. Start the engine and check for leaks. 3. Unfasten and remove the capscrews from both filter
covers.
Transmission Filter (B500)
The transmission filters require changing after the 4. Remove the cover, O-ring, gasket and filter element.
initial break-in period of 5,000 miles (8,000 km). 5. Pre-lube the element and install it in the reverse
Afterwards, filter changes should take place every order of installation.
25,000 miles (40,000 km) or 750 operating hours. 6. Tighten the capscrews to 38-45 ft-lbs (51-61 N·m).

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Filter/Reservoir 10. Reinstall the cover assembly and torque the center
Service the power steering reservoir filter element at bolt to 10 to 15 ft.-lbs. A new cover assembly is
approximately 225,000 miles (365,000 km). This is a recommended to prevent leakage at the cover
non-pressurized cartridge filter (Figure 3). gasket.
1. Drain the reservoir into a container by 11. Reconnect the hose at the power steering pump
disconnecting the filler hose from the power and tighten it securely.
steering pump inlet. 12. Refill the system with Dexron III ATF ONLY, using
the refilling procedure in this section Check the
CAUTION system for leaks.
13. Bleed the system as described below.
When draining fluid, use caution to avoid 14. Check for proper operation of the level sensor.
spilling it on the engine drive belts, as With the fluid at the proper level, the lamp should not be
contamination of this type requires belt lit. If the lamp is lit and the float type sensor is used, try
replacement. rotating the sensor 180˚ and recheck the sensor for
proper operation.
2. Check for correct operation of the sensor: with the
main battery disconnect switch on, turn on the 6
ignition switch. After the instrument panel start-up 1
test sequence is completed, the P/S Low indicator 9
should remain lit. If it does not, the sensor may be
7 2
defective. 3
3. Remove the reservoir cover by loosening the hex
bolt in the center of the cover (Figure 3). 4
4. Remove the level sensor from the side of the
11
reservoir body. Two types of sensors may be
present. The first type, a float design, is 14 8
position-sensitive and must be oriented correctly.
Note the direction of any arrows stamped into the
12
hex flats on the level sensor body. The second type
of sensor is optical, and is not position-sensitive. 5
5. Reach into the reservoir and remove the spring,
strainer assembly and filter element.
13
6. Clean the strainer washing it with cleaning solvent. If
the screen is damaged, replace the strainer 10
assembly.
7. Install the new replacement filter element, followed 1. COVER BOLT GASKET 8. SHELL
by the strainer and spring. 2. COVER GASKET 9. FILLER CAP
3. CARTRIDGE RETAINING 10. RESERVOIR INLET
8. Replace any old pipe thread sealant from the level SPRING 11. STRAINER
4. CARTRIDGE SUPPORT 12. SIGHT GLASS
indicator with fresh sealant of the proper type. WASHER 13. OUTLET
Reinstall the level sensor, paying attention to the 5. FILTER CARTRIDGE 14. SENSOR
6. COVER BOLT
previous orientation if the float type sensor was 7. FILLER NECK
used (the arrow should face up).
Figure 3. Power Steering Reservoir
9. Connect the electrical harness from the sensor.

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INSPECTION SCHEDULE (LUBRICATED COMPONENTS)

KEYS* DESCRIPTION METHOD SPECIFICATION CODE
INSPECT DAILY - SERVICE IF REQUIRED
1 Engine Lube Oil (Series 60) Inspect & Service S-2
2 Power Steering Reservoir Inspect & Service S-15
3 Wheel Bearings - Front & Tag Inspect & Service S-11 & S-12
4 Transmission (Automatic) Inspect & Service S-15 or S-15a
INSPECT EVERY 100,000 Miles (161,000 km) - SERVICE IF REQUIRED
24 A/C Compressor Oil Inspect & Service S-22 & S-28
3 Wheel Bearings and Seals Inspect & Service S-9 & S-10

FILTER MAINTENANCE SCHEDULE

KEYS* DESCRIPTION SERVICE INTERVAL METHOD
29 Engine Oil Filter Every 10,000 miles Change
35 Fuel Filter Every 10,000 miles Change
36 Transmission Oil Filter (Initial Fill) Initial 5,000 miles Change
36 Transmission Oil Filter (Normal) Every 25,000 miles Change
36 Transmission Oil Filter (Extended) Every 50,000 miles Change
31 Power Steering Filter (Reservoir) Every 225,000 miles Clean Strainer
33 Suspension Air Filter Every 75,000 miles Replace Element
34 Air Cleaner Every 5,000 miles Inspect/Replace
38 HVAC Air Filter Every 5,000 miles Inspect/Clean
N/A Auxiliary In-Line Air Filters Every 100,000 miles Replace Element
N/A Air Compressor Governor Air Filters Every 50,000 miles Inspect/Clean
N/A Air System Filter/Dryer (Desiccant) Every 300,000 miles Replace Element

CAPACITY SCHEDULE
Component Initial Factory Fill Service Fill
Allison B500/B500R Transmission 40 quarts U.S. (38 L) 26 quarts U.S. (23 L)
ZF Astronic Transmission (Optional) 2.9 gal. U.S. (11 L) 2.9 gal. U.S. (11 L)
Meritor Drive Axle 49 pints (23 L) 41 pints (19 L)
Detroit Diesel Series 60 Engine 38 quarts U.S. (36 L) 38 quarts U.S. (36 L)
Note: Capacities are approximate. Check dipstick levels with Fluid Level Check procedures.
Note: Capacities do not include filters.

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LUBRICATION SCHEDULE

KEYS* DESCRIPTION METHOD SPECIFICATION CODE**

SERVICE INTERVAL A - Every 5,000 Miles (8,000 km) or 150 Hours.
13 Differential Check level S-14a
24 A/C Compressor Mounting Pivot Zerk S-17

SERVICE INTERVAL B - Every 10,000 Miles (16,000 km) or 300 Hours.

19 Entrance Door Locking Claw Apply S-16
21 Entrance Door Hinges Apply S-16
20 Entrance Door Mechanism Apply S-17
1 Engine Crankcase Oil (Series 60) Drain & Fill S-2
14 Driveshaft Assembly Zerks (3) S-17

SERVICE INTERVAL C - Every 25,000 Miles (40,000 km) or 1,000 Hours.

4 Transmission Drain & Fill S-15

SERVICE INTERVAL D - Every 50,000 Miles (80,000 km) or 1,500 Hours.

22 Steering Column 2 Zerks S-17
28 Baggage & Service Doors Apply S-18
4 Transmission Drain & Fill S-15
11 King Pin Bushings Zerks (4) S-16
6 Steering Linkage Ends Zerks (6 front, 2 tag) S-16
4 Transmission and mounting components. Check for loose fasteners

SERVICE INTERVAL E - Every 80,000 Miles (130,000 km) or 2500 Hours.

Fan drive gear box and Fan driveshaft Drain & fill S-30

SERVICE INTERVAL F - Every 100,000 Miles (160,000 km) or 3,000 Hours.

3 Front and Tag Wheel Bearings Drain & Fill S-9 & S-10 or S-14a
13 Differential (Petroleum-based oil) Drain & Fill S-9, S-10 or S-11
37 A/C Compressor Clutch Assembly Zerk S-20
37 A/C Compressor Unloaders Apply S-25
N/A Brake Valve Apply S-26
4 Transmission (TranSynd) Drain & Fill S-15a

SERVICE INTERVAL G - Every 250,000 Miles (400,000 km)

13 Differential (Synthetic oil) Drain & Fill S-14a

* See Location Diagram (Figure 4) ** See Lubricant Specification Chart *** See Inspection
Schedule For Components

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COOLANT FILL AIR FILTER REMINDER POWER STEERING RESERVOIR

TRANSMISSION ---
DIPSTICK / FILLER TUBE

A/C COMPRESSOR
ENGINE OIL FILLER ENGINE OIL DIPSTICK FLUID LEVEL
GEAR BOX FILLER TUBE

J4500 ENGINE BAY FLUIDS & LUBRICANTS CHECKPOINTS

Dietroit Diesel S60 Engine

FIGURE 5. Recommended Daily Inspection chart

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 Date March 2003 Page 10-11

COOLANT FILL AIR FILTER REMINDER POWER STEERING RESERVOIR

TRANSMISSION ---
DIPSTICK / FILLER TUBE

A/C COMPRESSOR
GEAR BOX FILLER TUBE ENGINE OIL DIPSTICK FLUID LEVEL
& OIL FILLER

J4500 ENGINE BAY FLUIDS & LUBRICANTS CHECKPOINTS

Caterpillar C12 Engine

FIGURE 6. Recommended Daily Inspection Chart

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8 7 2 6 15
1 12

10
4

9 5
5
3
3

11
11

14

13

16
16

16

5 11

3 3

11

19
17
21

20

18 22

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PREVENTIVE MAINTENANCE SCHEDULE

The following preventive maintenance schedule is a compilation of suggested maintenance operations contained in
this maintenance manual.
Service intervals may be given as regular intervals (Reg. Int.) months and/or miles. Regular intervals must be
determined by shop personnel based on operating conditions, component failure history and previous experience. In
cases when both time (in months) and miles (in thousands) are given for a particular operation, maintenance should be
performed at whichever interval first occurs.

SERVICE INTERVAL (Miles)

Location Key
1 --- FRONT AXLE

Months

Reg Int

300,000
10,000

250,000
100,000

200,000
5,000

20,000

25,000

50,000
MAINTENANCE OPERATION

FRONT AXLE INSPECTION D

CHECK FRONT AXLE WHEEL ALIGNMENT D
LUBRICATE FRONT AXLE KNUCKLE PINS AND BUSHINGS 11 D
LUBRICATE TIE ROD ENDS 5 D

Location Key SERVICE INTERVAL (Miles)

2 --- REAR AXLE Months

Reg Int

300,000
10,000

250,000
100,000

200,000
5,000

20,000

25,000

50,000
MAINTENANCE OPERATION

CHECK DIFFERENTIAL OIL LEVEL D

INSPECT REAR AXLE D
DRAIN AND FILL DIFFERENTIAL (SYNTHETIC OIL) 13 12 D
DRAIN AND FILL DIFFERENTIAL (PETROLEUM-BASED OIL) 13 D

SERVICE INTERVAL (Miles)

Location Key

3 --- BODY
Months

Reg Int

300,000
10,000

250,000
100,000

200,000
5,000

20,000

25,000

50,000

MAINTENANCE OPERATION

INSPECT WINDSHIELD WIPERS D

INSPECT AND ADJUST ALL DOOR LINKAGES 6 D
INSPECT AND LUBE DRIVER’S SEAT D
INSPECT WALL AND ROOF SEAMS D
CHECK AND LUBRICATE ALL DOOR LOCKS D
LUBRICATE BAGGAGE/SERVICE DOORS 16 D
LUBRICATE ENTRANCE DOOR HINGES 21 D
LUBRICATE ENTRANCE DOOR MECHANISM 20 D
LUBRICATE ENTRANCE DOOR LOCKING CLAW 19 D

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 Date March 2003 Page 10-14

SERVICE INTERVAL (Miles)

4 --- BRAKES & AIR SYSTEM

Location Key

Months

Reg Int

300,000
10,000

250,000
100,000

200,000
5,000

20,000

25,000

50,000
MAINTENANCE OPERATION

INSPECT AIR RESERVOIR, VALVES, SWITCHES AND LINES D

INSPECT RESERVOIRS FOR MOISTURE 3 D
INSPECT AIR DRYER 3 D
DISASSEMBLE AIR DRYER AND REPLACE DESICCANT 36 D
INSPECT BRAKE COMPONENT FASTENERS D
INSPECT FRONT, DRIVE AND TAG AXLE BRAKE CHAMBERS 1 D
CLEAN AND INSPECT ALL BRAKE AND RELAY VALVES D
CLEAN AND INSPECT COMPRESSOR AND GOVERNOR D
CLEAN AND LUBRICATE ALL AIR CYLINDERS 17 D
CLEAN AND INSPECT PARK BRAKE CONTROL VALVE 6 D

SERVICE INTERVAL (Miles)

Location Key

6 --- COOLING SYSTEM Months

Reg Int

300,000
10,000

250,000
100,000

200,000
5,000

20,000

25,000

50,000
MAINTENANCE OPERATION

DRAIN AND CLEAN RADIATOR ASSEMBLY 12 D

CHECK COOLANT COMPONENTS AND COOLANT LEVELS D
LUBRICATE SHUTTER ASSEMBLIES D
CHECK COOLANT CONCENTRATIONS 1 D
CHECK FAN DRIVE BELT TENSIONS 2 D
INSPECT FAN CLUTCHES 3 D
REPLACE COOLANT FILTER 2 D
INSPECT WATER PUMP OPERATION 2 D

SERVICE INTERVAL (Miles)

7 --- ELECTRICAL SYSTEM
Location Key

Months

Reg Int

300,000
10,000

250,000
100,000

200,000
5,000

20,000

25,000

50,000

MAINTENANCE OPERATION

INSPECT VOLTAGE REGULATOR D

INSPECT STARTER D
TEST ALTERNATOR OUTPUT D

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SERVICE INTERVAL (Miles)

Location Key
8 --- ENGINE

Months

Reg Int

300,000
10,000

250,000
100,000

200,000
5,000

20,000

25,000

50,000
MAINTENANCE OPERATION

DRAIN AND FILL ENGINE CRANKCASE OIL 1 2 D

INSPECT TURBOCHARGER D
INSPECT EXHAUST SYSTEM D
REPLACE ENGINE OIL FILTERS 15 2 D
INSPECT ENGINE THERMOSTAT D
INSPECT INJECTORS AND VALVE LASH D
CHECK OIL TEMPERATURE AGAINST COOLANT TEMPERATURE 12 D

SERVICE INTERVAL (Miles)

Location Key
9 --- FUEL SYSTEM

Months

Reg Int

300,000
10,000

250,000
100,000

200,000
5,000

20,000

25,000

50,000
MAINTENANCE OPERATION

INSPECT FUEL SYSTEM D

REPLACE FUEL FILTERS 7 1 D
INSPECT THROTTLE DELAY D
INSPECT AIR CLEANER 12 D

SERVICE INTERVAL (Miles)

Location Key

11 --- STEERING
Months

Reg Int

300,000
10,000

250,000
100,000

200,000
5,000

20,000

25,000

MAINTENANCE OPERATION 50,000

CHECK AND FILL POWER STEERING RESERVOIR 2 D

LUBRICATE STEERING LINKAGE JOINTS 22 D
REPLACE POWER STEERING FILTER (RESERVOIR) 6 D
INSPECT AND LUBRICATE STEERING COLUMN 18 D

SERVICE INTERVAL (Miles)

Location Key

12 --- SUSPENSION
Months

Reg Int

300,000
10,000

250,000
100,000

200,000
5,000

20,000

25,000

50,000

MAINTENANCE OPERATION

CHECK RIDE HEIGHT D

INSPECT RADIUS ROD BUSHINGS D
INSPECT SUSPENSION AIR SPRING BELLOWS ASSEMBLIES D

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 Date March 2003 Page 10-16

SERVICE INTERVAL (Miles)

Location Key
13 --- TRANSMISSION

Months

Reg Int

300,000
10,000

250,000
100,000

200,000
5,000

20,000

25,000

50,000
MAINTENANCE OPERATION

ALLISON 500 / 500R TRANSMISSION

CHECK AND FILL TRANSMISSION FLUID D
INSPECT TRANSMISSION AND MOUNTING COMPONENTS D
DRAIN AND FILL TRANSMISSION FLUID 4 D
DRAIN AND FILL TRANSMISSION FLUID (TRANSYND) 4 D
REPLACE TRANSMISSION EXTERNAL OIL FILTER 9 D
REPLACE TRANSMISSION FILTER (TRANSYND) D
SERVICE TRANSMISSION INTERNAL OIL FILTER D
ZF ASTRONIC AUTOMATIC SHIFT TRANSMISSION (Optional)
CHECK TRANSMISSION GEAR OIL --- FILL AS REQUIRED D
INSPECT TRANSMISSION AND MOUNTING COMPONENTS D
DRAIN AND FILL TRANSMISSION GEAR OIL 4 D

SERVICE INTERVAL (Miles)

Location Key

14 --- DRIVESHAFT
Months

Reg Int

300,000
10,000

250,000
100,000

200,000
5,000

20,000

25,000

50,000
MAINTENANCE OPERATION

LUBRICATE DRIVESHAFT ASSEMBLY 14 1 D

SERVICE INTERVAL (Miles)

Location Key

15 --- WHEELS, HUBS & TIRES

Months

Reg Int

300,000
10,000

250,000
100,000

200,000
5,000

20,000

25,000

50,000

MAINTENANCE OPERATION

CHECK AND FILL WHEEL BEARINGS D

DRAIN AND FILL WHEEL BEARINGS (FRONT AND TAG) 3 12 D
INSPECT WHEEL BEARINGS AND SEALS 12 D

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 Date March 2003 Page 10-17

SERVICE INTERVAL (Miles)

16 --- HEATING AND A/C

Location Key

Months

Reg Int

300,000
10,000

250,000
100,000

200,000
5,000

20,000

25,000

50,000
MAINTENANCE OPERATION

REMOVE AND CLEAN EVAPORATOR FILTER D

INSPECT A/C/ COMPRESSOR ASSEMBLY D
LUBRICATE A/C COMPRESSOR MOUNT 10 1 D
LUBRICATE COMPRESSOR CLUTCH 8 D
INSPECT CONDENSER FAN AND MOTOR D
INSPECT HVAC BLOWER MOTOR ASSEMBLY D
INSPECT AND CLEAN PARCEL RACK EVAPORATOR MODULE D
CHECK COMPRESSOR OIL LEVEL D
CHECK REFRIGERANT LEVEL D

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SPECIFICATIONS
CODE DESCRIPTION SPEC/CLASSIFICATION GRADE TEMP. RANGE
S-1 Heavy Duty Engine Oil MIL-L-2104D/API: CD-II SAE 40
S-2 Heavy Duty Engine Oil MIL-L-2104D/API: CE SAE 15W-40
S-3 Heavy Duty Engine Oil MIL-L-2104D/API: SF/CD SAE 50 Above 10_F. (-12_C.)
S-4 Heavy Duty Engine Oil MIL-L-2104D/API: SF/CD SAE 30 Below 10_F. (-12_C.)
S-5 Heavy Duty Engine Oil MIL-L-2104D/API: SF/CD SAE 10W-40
S-6 Heavy Duty Engine Oil MIL-L-2104D/API: SF/CD SAE 10W
Marketer Trade Name
MOBIL DELVAC 1300 (S-1)
SHELL ROTELLA T (S-2)
MOBIL MOBIL ATF 210 (S-5)
UNOCAL GUARDOL (S-5)
TEXACO TL-1833 (S-5)
MOBIL MOBIL SUPER (S-3, S-4 & S-6)
TEXACO HAVOLINE SUPREME (S-3, S-4 & S-6)

CODE DESCRIPTION SPEC/CLASSIFICATION GRADE TEMP. RANGE

S-9 Multipurpose Gear Oil MIL-L-2105D/API: GL-5 SAE 85W-140 10_F. - 125_F.
S-10 Multipurpose Gear Oil MIL-L-2105D/API: GL-5 SAE 75W-90 -40_F. - 125_F.
S-11 Hypoid Gear Oil MIL-L-2105D/API: GL-5 SAE 85W-140 12_F. - 121_F.
S-12 Hypoid Gear Oil MIL-L-2105D/API: GL-5 SAE 75W-80 -40_F. - 121_F.
S-13 Mineral Gear Oil MIL-L-2105D/API: GL-1 SAE 90 Above 10_F. (-12_C.)
S-14 Mineral Gear Oil MIL-L-2105D/API: GL-1 SAE 80W Below 10_F. (-12_C.)
S-14a Synthetic Gear Oil MIL-L-2105D/API: GL-1 SAE 75W-140 down to ---40_F. (-40_C.)
Marketer Trade Name
MOBIL MOBILUBE HD (S-9 thru S-12)
CHEVRON ULTRA (S-9 thru S-12)
CHEVRON ARTIC (S-9 thru S-12)
MOBIL MOBILUBE C (S-13 & 14)
ROCKWELL O-76 Series (S-9-S-14a)

CODE DESCRIPTION SPEC/CLASSIFICATION GRADE

S-15 Automatic Transmission Fluid ATD C-4 DEXRON IIIE

Marketer Trade Name

MOBIL MOBIL ATF 220
EXXON SUPERFLO ATF
SHELL DONAX TG PLUS
ARCO ATF DEXRON/MERCON
TEXACO ATF MERCON/DEXRON IIIE M/P
S-15a Automatic Transmission Fluid TES295 ALLISON TRANSYND (synthetic)

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 Date March 2003 Page 10-19

SPECIFICATIONS (Cont’d)

CODE DESCRIPTION SPEC/CLASSIFICATION GRADE

S-16 Multi-Purpose Grease NLGI 6% Lithium/12-Hydroxy Stearate EP 1
S-17 Multi-Purpose Grease NLGI 8% Lithium/12-Hydroxy Stearate EP 2
S-18 Multi-Purpose Grease NLGI Neutral Lithium/Mineral Oil EP 1
S-19 Multi-Purpose Grease NLGI Clay-Base/Poly-Urea EP 1
S-20 Multi-Purpose Grease NLGI Paraffinic-Base/Poly-Urea EP 1

Marketer Trade Name

MOBIL MOBILITH AW-1 (S-16)
EXXON RONEX MP-2 (S-17)
LUBRIPLATE AERO (S-18)
SHELL DARINA EP 1 (S-19)
CHEVRON SR 1 (S-20)

CODE DESCRIPTION SPEC/CLASSIFICATION GRADE

S-23 Anti-Seize Compound N/A N/A

Marketer Trade Name

WITCO CORROSION CONTROL

CODE DESCRIPTION SPEC/CLASSIFICATION GRADE

S-24 Silicon Spray Compound N/A N/A
S-25 Silicon Fluid N/A N/A
S-26 Silicon Grease N/A N/A

Marketer Trade Name

DOW CORNING 316 (S-24)
DOW CORNING 200 (S-25)
DOW CORNING 55 O-RING LUBE (S-25)

CODE DESCRIPTION SPEC/CLASSIFICATION GRADE

S-27 Synthetic Manual Gear Lube API GL-3 EP SAE 50

Marketer Trade Name

EATON ROADRANGER CD 50
MOBIL MOBILTRANS SHC-50

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SPECIFICATIONS (Cont’d)

CODE DESCRIPTION SPEC/CLASSIFICATION GRADE

S-28 A/C Compressor Oil (R-134A) Ester-Based N/A

Marketer Trade Name

CASTROL SW-68 (ICEMATIC)
Mobil EAL Arctic 68
ICI Emkarate RL68H

CODE DESCRIPTION SPEC/CLASSIFICATION GRADE TEMPERATURE RANGE

S-29 Hypoid Gear Oil MIL-L-2105D/API: GL-5 SAE 80W-90 -30_F. - 121_F.

Marketer Trade Name

EXXON GEAR OIL GX
NOTE: Lubricant grade and/or viscosity shown are
Manufacturer-recommended.

CODE DESCRIPTION SPEC/CLASSIFICATION GRADE TEMP. RANGE

S-30 Fan gear box AGMA 5 Ep SHC 75W-90 15_F. - 125_F.

Marketer Trade Name

Hub City GL-90
Mobilube SHC 75W-90
NOTE: Lubricant grade and/or viscosity shown are
Manufacturer-recommended.

CODE DESCRIPTION SPEC/CLASSIFICATION TEMP. RANGE

S-31 Synthetic DIN 51524T2/ISO 7308 ---40oF to 266oF.

Marketer Trade Name

Pentosin CHF-11S
CRP Industries CHF-11S

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 Date March 2003

SECTION 11
STEERING SYSTEM

A - Steering System
B - Steering Wheel and Column
C - Power Steering Pump
D - Steering Gear TAS-85 Series

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SECTION 11A

STEERING SYSTEM
CONTENTS OF THIS SECTION
SUBJECT PAGE
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11A-2
Components and Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11A-2
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11A-3
Power Steering Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11A-3
Steering Linkage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11A-3
Filters and Reservoirs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11A-4
Filling the Power Steering System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11A-4
Filter Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11A-5
Bleeding the Power Steering System . . . . . . . . . . . . . . . . . . . . . . . . . . . 11A-6
Component Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11A-6
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11A-7
Torque Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11A-11
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11A-11

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GENERAL DESCRIPTION
The coach is fitted with a ZF hydraulically-assisted installed. It is linked to the steering gear input shaft by an
steering system. A LUK power steering pump provides intermediate steering shaft.
the hydraulic power, and Nelson provides the fluid
reservoir.

COMPONENTS AND OPERATION

Steering Gear
The Servocom Type 8098 steering gear is a compact, STEERING COLUMN WHEEL COVER
recirculating ball and nut design that combines the
power steering control valve and working cylinder in the
same housing as the steering mechanism.
STEERING WHEEL
Fluid Reservoir
STEERING SHAFT
The Nelson power steering fluid reservoir has a
suction-side filter inside the reservoir, and a fine mesh RELAY ARM
strainer below the filler opening. The reservoir has a
sight glass, dipstick and electronic sensor. Low fluid is
indicated by a telltale in the driver’s area. There is no DRAG LINK
in-line filter installed in the high pressure side of the
power steering system. STEERING
GEAR
Steering Linkage
CYLINDER
The relay arm is directly attached to the axle beam
and is supported by a large uni-pack bearing. It
transmits the fore and aft motion of the drag link to a side TIE ROD
to side motion of the intermediate drag link attached to
TIE ROD INTERMEDIATE DRAG LINK
the steer arm of the front axle. The two front wheels are ARM
connected via separate steer arms and a conventional
cross tube (tie rod).
Figure 1. Power Steering System
Pump
The LUK pump is gear-driven by the engine and uses
automatic transmission fluid as the hydraulic medium.
The fluid flows through seamless steel tubing in the
CAUTION
center tunnel and high pressure hose assemblies at a
maximum pressure of 150 bar (approximately 2200 psi). Due to the close proximity of the primary
coach control piping (i.e. power steering
Steering Wheel lines) within the center tunnel module to the
The steering wheel is 18 inches (457 mm) in diameter, underside of floorboards, use extreme
which is slightly smaller than usual. This provides a caution when making any alterations or
attachments to the floorboards in this area.
greater level of comfort to the driver. A tilt and telescopic
steering column manufactured by Douglas Autotech is

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MAINTENANCE
This section covers maintenance of the front steering Tapered Connection Inspection Procedure
system components. Maintenance of other key steering 1. Remove the cotter pin and loosen the castellated
components is covered in 2C: Alignment Procedure, nut fastening the steering drag link. Back it off three
11B: Steering Wheel and Column, 11C: Power full turns.
Steering Pump and 11D: Front Steering Gear. 2. Check for looseness in the tapered connection by
applying hand pressure against the drag link in a
POWER STEERING LINES direction away from the Pitman arm. DO NOT hit the
Keep power steering lines and hoses clean and check ball stud or drag link with a hammer, pry bar or other
regularly for cracks, abrasions and leaks. Ensure that object. If the taper connection is improperly seated,
clamps used to route hoses away from components are hand pressure will be enough to separate the parts.
secure and that proper routing is maintained. Repair 3. If the tapered connection stays together, reinstall
leaks immediately. the castellated nut and torque to 230 - 260 ft-lbs
Whenever a hose is disconnected, or if fluid has been (311-353 N.m). Install a new cotter pin (1/8” x
lost for any reason, bleed the system. See Bleeding the 1-1/2”). Do not back off the nut to insert the cotter
Power Steering System, page 11A-6. pin; if necessary, tighten nut to the next closest slot.

STEERING LINKAGE
The steering linkage ball joint ends are fitted with
CAUTION
grease fittings to allow regular lubrication. Refer to
Do not use repair methods (welding, plating,
Section 10 for recommended lubrication intervals. etc.) on steering components. Replace worn
The relay arm is not greaseable. It is fitted with a components with approved new parts.
pre-lubricated uni-pack type bearing assembly with a
flanged cap, and is serviceable by replacement of the
bearing assembly only. Relay Arm Inspection
The relay arm has a pre-lubricated uni-pack type
NOTE: Attempts to disassemble the bearing will bearing assembly with a flanged cap, and is serviceable
damage the bearing, which will then require by replacement of the bearing assembly only.
replacement. Disassembling the bearing will damage the bearing.
1. Inspect the relay arm for excessive play. If either of
Visually inspect the linkage components at every the following measurements is exceeded, replace
service interval. Check for bent or damaged the bearing assembly.
components. Check for loose components and a. Using a dial indicator mounted to the axle beam,
fasteners, worn joints and excessive play in the relay arm measure vertical end play at the bearing.
bearing. See Relay Arm Inspection (page 11A-3) for Maximum vertical play allowable is 0.005”.
allowable movement and Torque Chart (page 11A-11) b. Using a dial indicator mounted to the axle beam,
for torque values. measure the end of both arms at the linkage
If any fasteners come loose regularly, replace the connections. Maximum allowable vertical
fastener. Any time a component is replaced or adjusted, movement at either arm end is 0.125” (3 mm).
or a hard road contact with the wheels is reported, check 2. Inspect the bearing for freedom of rotation. If
the steering geometry and wheel alignment and correct necessary, replace the bearing.
it as necessary. Wheel alignment should also be a. With the linkages disconnected from both ends,
checked at scheduled intervals to maximize tire life and move the relay arm through its normal travel
steering system performance. See Section 2C. range. No roughness or spots of excessive
At major inspections or every 300,000 miles (480,000 resistance should be felt.
km) depending on operating conditions, inspect all b. The rolling resistance should not exceed 65
steering linkage components, including the Pitman arm, in-lbs. Using a spring scale connected to the
relay arm, all steering arms and the axle spindles using linkage connection tapered hole, pull the scale to
Magnaflux, Magnaglow or similar crack detection rotate the arm. The reading should not exceed 5
process. to 6 lbs.

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FILTERS AND RESERVOIRS FILLING THE POWER STEERING SYSTEM

The fluid reservoir and filter assembly is accessible NOTE: Do not run the power steering pump without
through the rear engine door and is mounted to the fluid in the reservoir. Damage to the pump can result.
frame member above the engine, near the 24V
1. Place the run switch at the rear electrical junction
alternator.
box to “Off” to prevent the engine from starting.
Any dirt, water or sludge in the power steering system
2. Fill the reservoir to the midway point of the sight
will severely affect the operation and life of the power
glass with fresh Dexron III ATF. Add the fluid to the
steering system components. If any foreign material is
filler spout at the top of the reservoir. A long-necked
discovered in the system, drain the system, flush it and
funnel is recommended to avoid spillage.
refill the system with fresh, clean Dexron III automatic
transmission fluid of the correct specification.
Check the fluid level in the reservoir at every service CAUTION
interval. It should also be a part of the driver’s pre-trip
inspection, along with other engine fluids. The reservoir Use caution when adding fluid to the
is equipped with both a dipstick attached to the filler cap reservoir: any spillage may fall on the drive
and a sight glass to display the fluid level in the reservoir. belts for the A/C compressor or alternator,
Use the sight glass for cold level checks only. The requiring replacement of the belts.
correct cold level is when the fluid level is at the middle of
the sight glass. 3. Using the start switch at the rear electrical junction
Use the dipstick for hot level checks only. The correct box, crank the engine until the fluid level in the
hot level is when the fluid level is between the add and reservoir goes below the sight glass. Do not exceed
full marks when the fluid is at its normal operating 10 seconds of continuous cranking. Stop cranking
temperature. when the level drops below the sight glass. Refill the
reservoir to the sight glass midpoint and crank the
A low level warning switch is also fitted to the reservoir,
engine again. Repeat this sequence until the fluid
which will trigger a warning lamp in the driver’s telltale
level stabilizes at the sight glass midpoint level.
cluster if the fluid level falls below the recommended
level.
Add fluid to the reservoir by removing the filler cap CAUTION
and dipstick assembly. A long-necked funnel is
recommended to avoid spillage. Spillage can result in Do not operate the pump without fluid in the
ATF contaminating the drive belts for the A/C reservoir.
compressor, causing replacement of the belts. Proceed
slowly, as overfilling can result in overflow during normal 4. Place the engine run switch to “Rear” and start the
operation. The correct filling procedure is given below. engine. Run the engine at idle for two minutes to
Do not overfill, as normal fluid expansion can cause bring the fluid to normal operating temperature,
overflow. while continuously monitoring the fluid level at the
sight glass. If at any time the fluid level falls below

CAUTION the sight glass, stop the engine by turning the run
switch to “Off,” refill the reservoir to the sight glass
midpoint level, and run the engine at idle again.
Do not operate the pump without fluid in the 5. Bleed the system. See page 11A-6.
pump reservoir. 6. When the fluid reaches normal operating
temperature, fill the reservoir to the proper level as
indicated on the dipstick attached to the filler cap.
NOTE: Do not overfill the reservoir beyond the
recommended level, as normal system operation
causes the level to rise periodically, causing overflow
if the level is too high.

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FILTER REPLACEMENT 6. Wash the strainer with cleaning solvent. If the

Replace the filter every 225,000 miles (365,000 km). screen is damaged, replace the strainer assembly.
The replacement procedure requires draining the
reservoir (Figure 2), so schedule filter replacement with
COVER BOLT GASKET
normal power steering fluid replacement. COVER BOLT
FILLER CAP
CARTRIDGE RETAINING
FILLER NECK SPRING

COVER GASKET

CARTRIDGE SUPPORT
STRAINER WASHER

SENSOR
SHELL

SIGHT GLASS

FILTER CARTRIDGE

Figure 2. Power Steering Reservoir

OUTLET
1. Drain the reservoir into a container by
disconnecting the filler hose from the power
steering pump inlet. RESERVOIR INLET

CAUTION Figure 3. Reservoir Filter Parts

When draining fluid, use caution to avoid 7. Install the new filter element, followed by the strainer
spilling fluid onto engine drive belts; this and spring.
contamination requires belt replacement.
8. Remove any old pipe thread sealant from the level
indicator, and replace it with fresh sealant of the
2. Check for correct operation of the sensor. With the proper type. Reinstall the level sensor, paying
main battery disconnect switch on, turn on the attention to the orientation if the float type sensor is
ignition switch. After the instrument panel start-up used. (The arrow should face up.) Connect the
test sequence is completed, the P/S Low indicator electrical harness from the sensor.
should remain lit. If it does not, the sensor may be
defective. 9. Reinstall the cover assembly and torque the center
bolt to 10 - 15 ft-lbs. A new cover assembly is
3. Remove the reservoir cover by loosening the hex
recommended to prevent cover gasket leakage.
bolt in the center of the cover (Figure 3).
10. Reconnect the hose at the power steering pump
4. Remove the level sensor from the side of the
and tighten it securely.
reservoir body. Two types of sensors may be
present. The first type, a float design, is 11. Refill the system with Dexron III ATF ONLY, see
position-sensitive and must be oriented correctly. page 11A-4. Check the system for leaks.
Note the direction of any arrows stamped into the 12. Bleed the system. see page 11A-6.
hex flats on the level sensor body. The second type 13. Check for correct level sensor operation. With the
of sensor is optical, and is not position-sensitive. fluid at the proper level, the telltale should not be lit.
5. Reach into the reservoir and remove the spring, If the telltale is lit and a float type sensor was used,
strainer assembly and filter element. rotate the sensor 180˚ and recheck the telltale.

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BLEEDING THE POWER STEERING 9. Install the new bearing assembly onto the arm using
SYSTEM the four fasteners. Torque the fasteners to the
Bleed the power steering system any time the specified value.
hydraulic system is opened and fluid has left the system,
allowing air to enter. The gear will bleed automatically,
but air from the gear will move into the return line. CAUTION
Bleeding evacuates air from the lines and into the
reservoir, where it escapes to atmosphere. Use caution to avoid cocking the bearing on
1. Ensure all power steering connections have been the spindle, and do not exceed 19,000 lb.
force while pressing the bearing all the way
made and are properly tightened.
to the spindle shoulder.
2. Fill the system as described on page 11A-4.
3. When the oil level has stabilized at the correct level, 10. Using a shop press and a suitable arbor, press the
start the engine and allow it to run at idle. arm and bearing onto the mounting bracket
4. Turn the steering wheel lock-to-lock at least six spindle.
times. Monitor the oil level in the reservoir 11. Install the roll pin and cap onto the spindle, making
constantly to ensure that the pump does not run sure to properly engage the cap onto the roll pin.
dry. Bubbles will rise in the reservoir until the air is
12. Install the retaining fastener and torque it to the
evacuated. Continue turning the steering wheel
specified value.
lock-to-lock until no bubbles are present.
13. Mount the relay arm and bracket assembly onto
5. When the bleeding is complete, fill the reservoir to
the axle beam, making sure to install and engage
the correct level and replace the cap. the dowel sleeves properly. Torque the fasteners to
the specified value.
COMPONENT REMOVAL
14. Connect the drag link and intermediate drag link to
Ball Joint Ends (Tapered Connections) the relay arm, torque the castellated nuts to the
1. Remove the cotter pin and castle nut from the ball specified value, and install the cotter pin.
joint stud. 15. Check the wheel alignment.
2. Separate the components. If necessary, use a
removal tool to break the connection.
Pitman Arm Removal
The Pitman arm uses a tapered spline connection that
Bearing Replacement requires a puller to separate the arm from the steering
1. Remove the relay arm assembly. gear sector shaft. The arm is indexed to the shaft; mark
the position before disassembly. Access to the
2. Mount the assembly in a heavy shop vise.
connection is made from the underside of the coach at
3. Remove the upper cap by removing the single the spare tire compartment floor.
fastener on top of the cap. Also remove the roll pin
1. Switch the main battery disconnect off.
engaging the cap with the spindle.
2. Raise the coach to a comfortable working height
4. Remove the four fasteners retaining the bearing
and securely block the coach. See Section 3F for
flange to the arm. Lower the arm over the bracket
jacking instructions.
spindle.
3. Remove the access cover from the spare tire
5. Using a suitable puller on the flange of the bearing,
compartment floor by removing the fasteners and
remove the upper portion of the bearing.
withdrawing the cover from the side service door
NOTE: It is likely that the lower bearing will remain on area.
the spindle. 4. The nut will be set in place to prevent it from
loosening. Use a punch to ease disassembly.
6. Withdraw the arm from the spindle. 5. Remove the nut.
7. Using a suitable puller, remove the remaining 6. Install a 2-jaw puller and use it to break free the
portion of the bearing from the spindle. tapered connection.
8. Clean the support bracket spindle and the bearing 7. Disassemble the drag link ball joint from the arm
bore on the arm. and remove the arm.

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TROUBLESHOOTING
Pump not delivering Drive in wrong direction of rotation. 1. Check the direction of the pump shaft
fluid rotation.
Pump driveshaft disengaged or sheared. 2. Remove the pump; determine damage
to cartridge parts; replace the sheared
shaft and damaged parts. See Power
Steering Pump.
Flow control valve stuck open. 1. Disassemble the pump and wash the
control valve in a clean solvent.
2.Return the valve to its bore and slide it
back and forth. It should move smoothly. If
the valve O.D. feels gritty, polish it with a
crocus cloth. Do not remove excess
material or round off valve edges. Do not
polish the valve bore.
3. Wash all parts before reassembling the
pump.
4. Flush the entire system thoroughly and
fill it with clean oil as recommended.
Vane(s) stuck in rotor slots. 1. Disassemble the pump, examine the
rotor slots for dirt, grime or small metal
chips.
2. Clean the rotor and vanes in a
good-grade solvent; reassemble the parts
and check for free vane movement.
Fluid viscosity too heavy to prime. Use fluid of the recommended viscosity.
Pump intake partially blocked. 1. Drain the system completely; flush it to
clear the pump’s passages.
2. Flush and refill the system with clean oil
as recommended.
Air vent for the oil reservoir clogged, or 1. Remove the filler cap and clean the air
dirty strainer. vent slot.
2. Check for clogged filter or strainer in the
tank.
3. Drain, flush and add clean oil to the
system.

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Pump making noise Restricted or partially clogged intake line 1. Drain the system, clean the intake line
or clogged filter. and strainers.
The pump must receive intake oil freely 2. Add new oil and strain by recommended
or cavitation will result. procedures.
Air leak at pump intake piping joints or 1. Test by pouring oil on joints and around
pump shaft seal. drive shaft.
2. Listen for a change in operation.
3. Tighten affected joints and replace the
pump drive shaft seal according to the
service instructions; refer to Power
Steering Pump.
Coupling misalignment. Realign and replace the oil seal and
bearings if they are damaged by shaft
misalignment.
Reservoir or manifold seal leakage. 1. Examine the reservoir inlet tube-to-pump
cover O-ring for cuts, nicks or dirt.
Leakage between manifold or reservoir 2. Replace as necessary. See Power
at the replenishing hole due to O-ring Steering Reservoir and Filter.
damage.
Hard steering either Insufficient pump pressure. 1. Check the pump pressure with a gauge.
while
hile pa
parking
ki g oor
2. If sufficient, check for the cause --- sticky
existing all the time
relief valve in pump or flow control.
Defective pump. Repair or replace defective parts.
Sticky control valve in pump or flow Replace valve. (May require total pump
control that prevents pressure build-up. replacement.) See Power Steering Pump.
“Lumpy” feeling (spots Delayed power application. Check and eliminate excessive free play in
of hard steering) steering linkage.
Air in steering system. Bleed the system.
Loose joints or linkage. Tighten as necessary.
Insufficient oil flow. 1. Check for damaged hoses, weak or
sticking valve spring or worn pump parts.
2. Repair or replace parts as necessary.
Low oil supply. Check the oil level and refill.
Hard steering Air in the system. Bleed the system.
acco pa ied b
accompanied by
Pump malfunction. See Power Steering Pump.
abnormal noise
Low oil supply. See Power Steering Pump.

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No recovery from turn Insufficient caster. Increase caster; see Sections 1 and 2C.
to st
straight
aight ahead
Tight ball socket connections and other Loosen the connections but keep them
linkage connections. snug.
Tight front axle spindles. Adjust the linkage.
Spool in steering gear valve sticking. Repair or replace the steering gear.
(Prevents centering of valve.)
Tire pressure low. Check the pressure and inflate the tires as
required.
Front end out of alignment. Align the front end; see Sections 1 and
2C.
Steering column binding. Eliminate the bind; refer to Steering
Column.
Pump flow insufficient. Check the pump pressure with a gauge. If
it is insufficient, check for the cause and
repair the pump and/or lines; refer to
Power Steering Pump.
Shimmy Loose ball socket connections or other Tighten.
linkage connections.
Wheels out of balance. Balance the wheels.
Wheel bearings improperly adjusted or Check the bearings; replace them if
worn. necessary.
Excessive caster. Correct and have the front alignment
checked to specifications.
External oil leakage Finding the location of the leak may be 1. Check all fittings, clamps, hoses and the
difficult, as oil may “run” away from leak pump.
point on the bear of the chassis
chassis.
2. Repair or replace any possible causes of
leakage.
Excessive pump Kink in oil return line. Relocate the line to remove the kink.
pressure with steering
gear in neutral position
Other causes of hard Caster and camber degree incorrect. Correct to specification; see Front End
steering Alignment.
Air in the system. Bleed the system and check for the source
of air.

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Lost motion or lash at Steering wheel loose on the shaft. Tighten the steering wheel to
steering wheel specifications.
Loose connection between gear and Tighten the connections; see Steering
steering column. Column.
Steering gear loose on frame. Tighten the steering gear.
Pitman arm loose on sector shaft. Tighten the Pitman arm.
Components in the steering linkage Tighten or replace the components where
loose or worn. necessary.
Steering gear worn. Repair or replace the steering gear.
Restricted hose or line due to kink or Relocate the line or hose to remove the
severe bend. kink.
External oil leakage Rubber relief (vent) plug leaking at the Replace the oil seal.
side cover indicates failure of the sector
shaft oil seal in the side cover

CAUTION
If the hydraulic system fluid becomes overheated, it can cause the seals in the steering gear to
shrink, harden or crack and lose their sealing ability.

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TORQUE CHART

120-170 ft lbs

45-60 ft lbs

60 ft lbs

410 ft lbs
(5 places)
210 ft lbs
210 ft lbs
40 ft lbs (CLAMPS)

Pitman arm nut 405 ft lbs 210 ft lbs

Torque Chart

SPECIFICATIONS
DRAG LINK
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . O&S
PITMAN ARM
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ISP

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SECTION 11B

STEERING WHEEL AND COLUMN

CONTENTS OF THIS SECTION

SUBJECT PAGE
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11B-3
Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11B-3
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11B-4
Lubrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11B-4
Column Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11B-4
Column Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11B-4
Troubleshooting the IPX Master . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11B-6
Torque Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11B-7
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11B-8

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FULLY FORWARD
STEERING COLUMN
POSITION NOMINAL STEERING
COLUMN POSITION

FULLY DOWNWARD STEERING

COLUMN POSITION

STEERING COLUMN
MOUNTING BRACKET

STEERING COLUMN

FIGURE 1

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GENERAL DESCRIPTION
CAUTION
The steering column assembly transfers the rotation
of the steering wheel to the power steering gear. Electronics are sensitive to static electrical
The tilting/telescoping column makes the steering discharge. They are safe when installed and
properly connected in the vehicle. Do not
wheel adjustable for height and distance from the driver.
apply power to any part of the multiplex
system until all components (the master and
the steering wheel) are mounted and
COMPONENTS properly connected.
The lower section consists of a splined shaft that
connects to upper section U-joint, and another lower The multiplex system includes two major
clamping yoke U-joint assembly that couples to the components: the steering wheel (with switches), and the
steering gear’s input shaft. IPX master located under the dash (Figure 2). These two
components are connected by wires that pass through a
“clock-spring” assembly in the steering column. The IPX
Tilt/Telescoping Steering Column master contains relays that are activated by the switches
on the steering wheel. The relays are then connected to
The tilt/telescoping steering column (Figure 1) is the cruise, horn and optional engine brake control
designed with an upper and lower section. The steering system.
wheel mounts to an upper wheel tube that slides over the
housing-mounted internal U-joint assembly, and, in turn,
connects to a lower U-joint and clamp yoke assembly IPX MASTER
that composes the upper section.
The lower section consists of a splined shaft that
connects to the upper section U-joint. It incorporates a
lower U-joint and clamping yoke at the steering gear
joint.
The upper tilt/telescoping section features a wear
compensating mechanism that provides vibration- and
rattle-free performance.
A single lever controls tilt and telescope functions. It is
mounted on the left side of the column. Pulling the lever
toward the steering wheel allows tilting; pushing the
lever inward allows telescoping.
The tilt angle adjusts to four positions. Telescoping
can be done in small increments through approximately
a two-inch range. A sequential tilt/latch mechanism
ensures positive latching and locking of the column at
the 7-degree intervals.

IPX Master
The IPX master controls the horn, cruise control and
engine brake. It receives signals from switches mounted
on the steering wheel through a wire harness. FIGURE 2

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MAINTENANCE
WARNING
LUBRICATION
All steering mechanisms are safety critical
Grease the steering column U-joints at 50,000 mile items. These instructions must, therefore, be
(80,000 km) intervals per the lubrication specification followed. Failure to observe the procedures
chart in Section 10. Remove the steering column cover and instructions may result in loss of
for access to the grease fitting. steering. If inspection or testing reveals
evidence of abnormal wear or damage to the
tilt column assembly, or if you encounter
circumstances not covered in the manual,
COLUMN REMOVAL
1. Switch the battery disconnect OFF. STOP.

2. Unfasten and remove the steering column cover Consult the MCI service department. Do
assembly. not repair or service a tilt column assembly
that has been damaged or shows
3. Remove the wheel nut and pull the steering wheel excessive wear.
off the shaft spline.

WARNING
CAUTION
To prevent injury, use extreme care when
Use a suitable “wheel puller” to remove using flammable cleaning solvents.
the steering wheel.

COLUMN INSTALLATION
4. Disconnect the harness from the IPX master located
on the right-hand side of the column support
bracket.
CAUTION
5. Remove the screws that secure the turn signal
assembly, and remove it from the steering column. When installing the steering column, make
sure no debris is around the lower column
6. Remove the lower shaft yoke clamp that connects where it passes through the floor. Debris
the lower column section to the steering gear’s can cause the steering column to bind.
input shaft. Proper installation of covers and seals
keeps debris from interfering with steering.
7. Remove the capscrews that secure the upper
column section’s housing to the mounting bracket.
The steering column may now be lifted out of the 1. Installation is the reverse or Removal. Torque
coach as a complete unit. fasteners as shown in Torque Chart.

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1. CENTER PAD (WHEEL)

2. NUT (WHEEL)
3. STEERING WHEEL
4. STEERING COLUMN ASSY
5. TURN SIGNAL ASSY
6. MOUNTING BRKT
7. CAPSCREW
8. COVER UPPER
11. COVER
12. GAP HIDER
17. STEERING SHAFT
18. CAPSCREW

FIGURE 3

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Printed in Canada.
 Date March 2003 Page 11B-6

TROUBLESHOOTING THE IPX MASTER If signal wire continuity is established and the system
is still non-functional, detach the steering wheel switch
The most common problems with electrical devices pads from the wheel and check that the connectors to
are wires and connectors. Check that all connectors are the switch boards are fully seated. This can be done
secure and wires are not damaged without removing the wheel from the column. Remove
the screws on the back of the steering wheel to detach
the switch pads (Figure 4). Verify the connections and
If the system is partially functional, the problem is re-attach the switch pads.
likely with the wiring between the IPX master and the
cruise control system. If the system is completely If the system is still non-functional, replace
nonfunctional, check the wiring to the master. components in the following order: IPX master, switch
pad(s), steering wheel.
Check the signal path of the harness as follows:

1. Switch the battery disconnect OFF.

2. Remove the center pad from the steering wheel. STEERING WHEEL (BACK)
3. Disconnect the harness at the hub of the steering
wheel.
4. Disconnect the harness at the base of the column.
5. Check for continuity and shorts from the connector
at the steering wheel to the connector at the base of
the column.
6. Inspect the clock-spring assembly for cracks or
damage.
7. Replace the center pad on the steering wheel.
8. Switch the battery disconnect ON.
9. Test the system.

The electrical connections from the top of the column

to the bottom travel through a clock-spring assembly
that is part of the column telescoping mechanism. A lack
of continuity on one of the wires usually indicates that
one of the clock-spring wires may be damaged. If this
seems to be the case, refer to the steering column
service information for assistance. FIGURE 4

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Printed in Canada.
 Date March 2003 Page 11B-7

TORQUE CHART

40-- 50 ft lbs

45-- 50 ft lbs
45-- 50 ft lbs

45-- 50 ft lbs
45-- 50 ft lbs
45-- 50 ft lbs
45-- 50 ft lbs

Torque Chart

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Printed in Canada.
 Date March 2003 Page 11B-8

SPECIFICATIONS
STEERING COLUMN
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Douglas
STEERING WHEEL
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VIP
TURN SIGNAL SWITCH ASSEMBLY: (12-VOLT SYSTEM)
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sprague
IPX MASTER CONTROL
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VIP

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Printed in Canada.
 Date March 2003 Page 11C-1

SECTION 11C

POWER STEERING PUMP

CONTENTS OF THIS SECTION

SUBJECT PAGE
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11C-1
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11C-1
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11C-3

GENERAL DESCRIPTION MAINTENANCE

The LUK pump (Figure 1) is gear driven by the engine The only serviceable parts are in the seal kit, MCI part
and uses automatic transmission fluid as the hydraulic number 11-09-1006. Figure 2 shows an exploded view
medium for the front steering system. The pump has of the pump and identifies the seal kit parts.
large displacement and high flow ratings. The fluid flows
through seamless steel tubing in the center tunnel and PERIODIC MAINTENANCE
high pressure hose assemblies at a maximum pressure Every 50,000 miles (80,000 km) or six months,
of 150 bar (approximately 2200 psi). replace the hydraulic system fluid.

1. POWER STEERING PUMP

2. POWER STEERING RESERVOIR
3. OIL GALLERY LINE
4. P/S RETURN LINE
5. P/S SUPPLY LINE
6. RESERVOIR VENT HOSE
7. TEMP. GAUGES

Figure 1. Power Steering Pump

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 Date March 2003 Page 11C-2

1. HOUSING
2. 0-- RING
3. 0-- RING
4. SUPPORT PLATE
5. VANE
6. RING
7. WEAR PLATE
8. ROTOR
9. PRESSURE PLATE
10. SPRING
11. DOWEL PIN
12. O-- RING
13. S/A FLANGE
14. SHAFT
15. RETENTION RING
16. SHAFT SEAL
17. SNAP RING
18. O-- RING
19. SHIPPING PLUG
20. PRESSURE PORT FITTING
21. O-- RING
22. S/A CONTROL VALVE
23. SPRING
24. VALVE STOP
25. SCREW
26. WASHER
27. SHIPPING PLUG

Figure 2. Power Steering Pump

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Printed in Canada.
 Date March 2003 Page 11C-3

SPECIFICATIONS
POWER STEERING PUMP
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Luk
Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Luk LF93
Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Vane
Rotation (Viewed From Shaft End) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Counter Clockwise
Mounting Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Gear Case Front
Maximum Output Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2203.5 psi (15,204 kPa)

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Printed in Canada.
 Date March 2003 Page 11D-1

SECTION 11D

STEERING GEAR
CONTENTS OF THIS SECTION

General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11D-1

Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11D-1
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11D-3
Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11D-3
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11D-3
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11D-4

GENERAL DESCRIPTION
The ZF Servocom Type 8098 steering gear (Figure 1)
is a compact, recirculating ball and nut design that
combines the power steering control valve and working
cylinder in the same housing as the steering
mechanism. The steering gear features a high quality
surface finish for the piston and steering sector gear
teeth and an optimized tooth contact pattern. Large
recirculating balls and needle roller thrust bearings
combine to reduce wear. A special sector shaft gearing
design, and gear backlash adjusted by eccentric sector
shaft bearings provide precise steering action with
near-zero play in the central position. The steering gear
features a control valve characteristic custom-designed
for the coach, which provides a high degree of on-center
feel and returnability with low lock-to-lock effort.

COMPONENTS
The steering gear is made up of several internal and Figure 1. ZF Servocom Type 8098
external components (Figure 2). Most of the gear’s
internal components are addressed for disassembly,
repair and reassembly in the manufacturer’s service
manual.

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Printed in Canada.
 Date March 2003 Page 11D-2

1. Housing 24. Rocker shaft 47. Grub screw

2. 0--ring 25. Piston assembly 48. Collar nut
3. Washer 26. Piston 49. Worm assembly
4. Housing cover 27. Set of balls 50. Snap ring
5. Gasket 28. Recirculating ball tube (two halves) 51. Sliding tube
6. Backing ring 29. Plug 52. 0--ring
7. Oil seal 30. Gasket 53. Sealing ring
8. Washer 31. Shim 54. Pin
9. Needle cage 32. Pin 55. Plug
10. Rating plate 33. 0--ring 56. Sealing ring
11. Notched pin 34. Sealing ring 57. Housing
12. Grub screw 35. Sealing ring 58. Needle sleeve
13. Collar nut 36. Sealing ring 59. Shim
14. Pressure limiting valve 37. 0--ring 60. Bevel wheel
15. 0--ring 38. Gasket 61. Outer shaft sealing ring
16. Screw 39. Needle cage 62. Inner shaft sealing ring
17. 0--ring 40. Washer 63. Adjusting screw
18. Recuperation valve 41. 0--ring 64. Slotted nut
19. Locknut 42. Sealing ring 65. Dust cap
20. Dust seal 43. 0--ring 66. Bevel wheel
21. Plug 44. Cylinder cover 67. Ball bearing
22. Sealing ring 45. Washer 68. Stud
23. Locking screw 46. Hex head screw 69. Intermediate flange
70. 0--ring
71. Ball bearing
72. Cross recessed washer

Figure 2. Steering Gear Components

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Printed in Canada.
 Date March 2003 Page 11D-3

MAINTENANCE

REMOVAL
1. Open the front J-box and spare tire doors.
2. Remove the spare tire and locate the steering gear.
3. Remove the drag link cover and steering shaft
(Figure 3).
4. Remove the nut that connects the drag link to the
steering gear (Figure 3). STEERING GEAR
5. Clean the area around the fittings.
6. Disconnect all hydraulic lines connected to the
steering gear and plug the holes to prevent
contamination.
GEAR BRACKET
NOTE: When disconnected, the lines from the gear
will leak; cap the ends of the lines.

7. Separate the strap lock from the five (5) steering

gear mounting bolts STRAP LOCK

NOTE: When the strap lock has been removed, it

cannot be reused; a new strap lock must be used
when installing the steering gear
Figure 4. Steering Gear Removal

8. Take out the five (5) bolts that hold the gear to the INSTALLATION
mounting bracket and carefully remove the gear 1. Install in the reverse of Removal.
with the pitman arm attached (Figure 4).
NOTE: Install a new strap lock plate. Refer to the
Parts Manual, Section 11 for the part number.

WARNING 2. When the steering gear and strap plate have been
installed, tighten mounting bolts to specified
The steering gear weighs approximately torque, then form the strap lock against at least two
110 lbs. (50 kg) dry. Before continuing flats of the capscrew head and over the mounting
with the removal procedure, support the bolts using a flat punch and hammer.
gear to prevent it from falling from the 3. After the steering gear is installed and the drag link
frame after the mounting bolts have and hydraulic lines have been attached and
been removed. torqued, top up power steering fluid and bleed the
system.

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Printed in Canada.
 Date March 2003 Page 11D-4

SPECIFICATIONS
STEERING GEAR
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ZF Friedrichshafen AG
Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Servocom Type 8098
Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.1:1, 22.2:1
Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Vane
Rotation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Clockwise (viewed from shaft end)
Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Driver’s Floor Frame
Operating Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 bar max.

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Printed in Canada.
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 Date March 2003

SECTION 12
SUSPENSION SYSTEM

A - Suspension Control Systems

B - Front, Drive and Tag Axle Suspension

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Printed in Canada.
 Date March 2003 Page 12A-1

SECTION 12A

SUSPENSION CONTROL SYSTEMS

CONTENTS OF THIS SECTION
SUBJECT PAGE

General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12A-2

Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12A-2
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12A-3
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12A-4
Leveling Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12A-4
Manual Tag Unloading Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12A-5
Electric Tag Unloading Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12A-5
Quick Recovery Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12A-6
Pressure Protection Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12A-7
Relay Valve R-12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12A-8
In-Line Air Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12A-8
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12A-9

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Printed in Canada.
 Date March 2003 Page 12A-2

GENERAL DESCRIPTION
The suspension system uses three mechanical Manual Tag Unloading System
leveling valves to control ride height by regulating air Tag axle unloading operates through two Watts full
flow to and from the air springs. port, two-position, manual dump valves located inside
The suspension system has a kneeling function that the curbside rear side service door. They are supplied by
allows the operator to lower the coach by 5” (180 mm) at the rear leveling valve circuit, through the drive axle air
the front axle when the coach is stopped. spring supply lines. The manual tag unloading system
The coach is equipped with manual tag axle dump can completely exhaust the tag air springs.
valves, located in the curbside rear service Optional Electrical Tag Unloading System
compartment. These valves are used to completely
The optional electrical tag unloading system is
dump the tag axle air springs prior to lifting the coach. composed of two normally-open solenoid valves for
An optional, electrical tag axle unloading feature unloading, two normally-closed solenoid valves for
allows the operator to reduce air pressure in the tag axle holding, and one low-pressure switch. The valves are
air springs, increasing drive axle loading. This feature is mounted above the tag axle.
used in low traction situations. The unload system is
protected by a low air switch and alarm. Optional Rear Rise System
An optional rear rise feature allows the operator to The major components of the rear rise feature are:
raise the rear bumper approximately 3” (76 mm) above one Skinner solenoid control valve, a pressure
normal ride height. The rear rise feature operates at protection valve (set at 85 psi) and a pressure reduction
speeds under 20 mph, and is used to prevent rear valve. The valves are mounted on the rear rise air tank,
bumper scuffing. located inside the engine compartment near the
right-hand wheelhousing. Two two-way check valves
and one R12 relay valve are mounted on the brake
COMPONENTS component channel above the drive axle.

Leveling Control System Pressure Protection System

The coach has one leveling valve for the front Air spring pressure is protected by a normally-closed,
suspension, and two valves for the rear suspension. two port, non-exhausting pressure protection valve
Valves are mounted to the body, and valve levers are (PPV) located in the central heat compartment. This
connected to the axles by link assemblies. Leveling valve isolates the leveling valves to protect them from
valves are supplied by the suspension/accessory low air conditions.
junction blocks and deliver air to the air springs. The kneeling and the rear-rise features have pressure
protection valves to protect their systems. The kneeling
Kneeling System PPV prevents complete air spring deflation.
The kneeling system incorporates an electrically-
controlled kneeling module, two pressure switches and Suspension Filters
the front leveling valve. The kneeling module controls Several filters are installed in the suspension air lines
front suspension air spring pressure during kneeling to prevent contaminants from entering valves and other
and quick recovery modes. One pressure switch signals components. The main suspension filter is connected to
recovery mode cut-out. The other pressure switch the supply reservoir supply port. Other in-line filters are
signals kneeling cut-out. located upstream of the leveling valves.

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Printed in Canada.
 Date March 2003 Page 12A-3

OPERATION springs are supplied by the leveling valves along with the
drive axle air springs. Two holding, normally-closed
Leveling Control System solenoid exhaust valves are closed, preventing air from
Leveling valves are mounted to the coach body with exhausting.
lever linkages attached to the suspension structure. At
When the switch is positioned to unload, the two
normal ride height, the leveling valve and lever are in the
normally-open solenoid valves close to isolate the tag air
neutral position. Air does not flow into or exhaust from
springs from the drive axle air springs. The two
the air springs.
normally-closed solenoid exhaust valves open to reduce
When loading the coach, the body moves down and the air spring pressure to 40 psi.
the lever rotates up. The valve allows air to flow into the
air springs, raising the coach. NOTE: With the electrical tag unloading feature, the
When unloading, the body moves up and the lever tag axle air springs will not unload to 0 psi.
rotates down. The valve exhausts air from the air
springs, lowering the coach. Optional Rear Rise System
The coach raises or lowers until the lever returns to The leveling valves control the air spring pressure
neutral. The valves have a range for the neutral position through the double check valves. The normally-closed
so small lever movements do not activate it. solenoid valve exhausts the R12 relay valve control line.
Kneeling System When rear rise is enabled, the solenoid valve opens,
During normal coach operation, the kneeling module applying 100 psi to the R12 control port. Air from the rear
is inactive. The module’s valving allows the front leveling rise tank, through the double check valves, inflates the
valve to control ride height. air springs and raises the rear of the coach. A 10 psi
When the kneel switch is pressed, the kneeling pressure switch closes when the supply line is
module is activated. The module locks out the leveling pressurized, lighting the telltale and sounding the
valve’s control of the air springs and exhausts the air buzzer. Above 20 mph, the solenoid closes, returning
springs. The front of the coach is lowered as the air height control to the leveling valves. When speed drops
springs are exhausted. The kneel cut-out pressure below 15 mph, the valve reopens.
switch signals the module when the pre-set kneel When the rear rise system is set to lower, the solenoid
pressure is reached. The module will stop exhausting air switch closes, exhausting the R12 control line. Height
and maintain the kneel position until recovery. control is returned to the leveling valves.
When the recovery switch is pressed, the kneeling
module goes into recovery mode. The leveling valve’s NOTE: Always set the rear rise system to LOWER
control of the air springs remains locked out. The before any suspension maintenance or inspections.
module inflates the air springs directly from the
suspension reservoir. This “quick recovery” speeds the
air spring inflation. When the air springs approach Pressure Protection System
normal operating pressure, the recovery cut-out The pressure protection valve controls and isolates
pressure switch signals the module. The module stops the supply air to the suspension/accessory air system.
inflating the air springs and is deactivated. The leveling Additional pressure protection valves are used in the
valve regains control of the air springs, making the small kneeling and rear rise systems.
final height adjustments. The main pressure protection valve, located in the
central heating compartment, is set to close at 80 psi
Tag Axle Unloading (Manual)
and open at 95 psi.
When manually unloading the tag axle, the unload
valves block the air supply from the rear leveling valves When supply side air pressure reaches 95 psi, the
and completely exhaust the tag air springs. When piston moves up, the inlet valve opens and air passes
loaded, the exhaust valve is closed and the tag air through the delivery side. When air pressure drops
springs are inflated by the rear leveling valves. below 80 psi, the spring forces the piston down, closing
the valve and protecting the supply side from further air
NOTE: The manually-operated tag unload valves can loss.
completely exhaust the tag axle air springs. The pressure setting is determined by adjustable
spring force, which is controlled by the cap. Turn the cap
Tag Axle Unloading (Electrical) clockwise to increase the pressure setting,
Normally, the tag axle is loaded. Two unloading, counter-clockwise to lower the setting. Tighten the
normally-open solenoid valves are open and the tag air locknut after adjustment.

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Printed in Canada.
 Date March 2003 Page 12A-4

MAINTENANCE
LEVELING VALVE 4. Disconnect the valve linkage and pull down to
exhaust remaining air from air springs.
Ride Height Adjustment 5. Disconnect the air lines from valve and cover the
The normal body-to-axle clearance is 11” (280 mm). ends with tape to prevent contamination.
This dimension is measured from the top surface of the
6. Remove the valve from the body.
bottom air spring support plate to the bottom surface of
the top support plate. Leveling Valve Leakage Test
It should not be necessary to make an adjustment
under normal service conditions. However, if an NOTE: Check all suspension circuit in-line filters and
adjustment is necessary, it can be made by changing line connections to and from the leveling valve for
the position of the lever at the link’s fixed attachment leakage or blockage before testing the valve.
point.
1. Clean the exterior of the valve assembly.
2. Connect an air line to the valve inlet port, and apply
air pressure 70-100 psi (480-690 kPa).
3. Coat the valve assembly in soap solution and watch
Do not access suspension components from for air bubbles when the lever is in the center
the wheel wells. Unintentional actuation of position. No air should escape from any point of the
the height control valves can result in serious valve assembly.
injury. Always block the coach body during 4. If bubbles appear from an outlet (air spring) port,
inspections and repairs. replace the valve.
5. Remove the air line from the inlet port and connect it
1. Fill coach air system completely. to the outlet (air spring) port. If bubbles appear at
the air inlet, the valve is defective. Replace the valve.
2. Switch battery disconnect off.
6. If bubbles appear at the exhaust port, it is an
3. Locate the suspension system height control valve
indication that the exhaust valve is defective and
responsible for the condition.
that the leveling valve should be replaced.
4. Loosen the link from the rod collar. 7. If bubbles appear around edge of the valve cover
5. Move the collar up or down and tighten. plate, the valve must be replaced.
Leveling Valve Removal 8. If no leaks are found, remove the valve assembly
from the water and blow out all passages.
1. Switch battery disconnect off, block the coach and
vent the entire air system. Leveling Valve Installation
2. Support the coach by placing blocks under joist 1. Install leveling valves in reverse order of Leveling
bumper points. Valve Removal. Torque mounting fasteners to 9
3. Open drain cock in air filter and vent all air from lb-ft (12 Nm).
system. 2. Torque linkage fasteners to 17 lb-ft (23 Nm).

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 Date March 2003 Page 12A-5

TAG UNLOADING VALVE (MANUAL) TAG UNLOADING VALVE (ELECTRIC)

Every 50,000 miles (80,000 km) or 1500 operating Every 100,000 miles (160,000 km) or 3600 operating
hours, test the valve. (Figure 1) See Manual Unloading hours, disassemble, clean and inspect the plunger,
Valve Operating Test and Manual Unloading Valve spring, piston and seals. Replace damaged parts.
Leakage Test.
Electric Unloading Valve Removal
1. Switch battery disconnect off, block the coach and
vent the entire air system.
2. Label and disconnect all air lines and fittings, and
remove the wire harnesses from the solenoid
assemblies.
3. Unfasten the regulator valve mounting screws and
remove regulator/solenoid valve assembly from
panel.
4. Remove solenoid valves from regulator plumbing.

Electric Unloading Valve Disassembly

1. Remove the sleeve adapter, adapter seal, housing
nut and housing.
2. Remove coil assembly from housing if necessary.
C0390 3. Remove sleeve from body.

FIGURE 1

CAUTION
Manual Unloading Valve Operating Test
With air pressure in the tag suspension system, Do not use a wrench on the sleeve; it could
operate the valves to exhaust and refill the air springs. damage the sleeve.
Check that the Low Tag telltale lights when the air
springs are exhausted.

Manual Unloading Valve Leakage Test 4. Remove spring, plunger and flanged seal from
With the valves in the normal (fill) position, apply soap body.
solution. If leakage at the exhaust port or valve stem
exceeds a one inch bubble in five seconds, replace the NOTE: Wash plunger assembly, seals and o-rings in
valve. mild soap and water solution only.
Manual Unloading Valve Removal
1. Switch the battery disconnect OFF. 5. Apply mineral oil to the flanged seal, and reinstall
2. Block the coach and vent the entire air system. into valve body.
3. Label and disconnect all air lines, fittings and wire 6. Install plunger and spring in sleeve. Tighten sleeve
harnesses from the low air warning switches. into body to 11 lb-ft (15.4 NSm).
4. Remove the valve handle hex nut. 7. Install coil into housing, and assemble housing
5. Remove the valve from the bracket. components in reverse order. Tighten nut to 35 lb-in
(4.1 NSm).
Manual Unloading Valve Installation
8. Install onto module assembly.
1. Install in the reverse order of Manual Unloading
Valve Removal. 9. Connect air lines and electrical harness.
2. Torque mounting fasteners to 20 lb-ft. 10. Test valve operation.

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 12A-6

QUICK RECOVERY VALVE 4. Remove the quick recovery valve from the plumbing
Every 100,000 miles (160,000 km) or 3600 operating assembly.
hours, disassemble, clean and inspect. Quick Recovery Valve Disassembly
1. Unfasten the hex nut on top of the coil assembly.
NOTE: Valve need not be removed from the line to be
disassembled, cleaned and inspected or for solenoid 2. Remove the coil and wave washer from valve.
replacement. 3. Unfasten and remove sleeve assembly.
4. Remove the plunger, return spring and O-ring
flange seal.
Solenoid Replacement 5. Unfasten top cover screws and gently lift cover off.
1. Switch battery disconnect off.
NOTE: Take care not to damage cover or body of
2. Follow steps 1 and 2 of Quick Recovery Valve
valve.
Disassembly.
3. Install new coil and follow steps 1 and 2 of Quick 6. Remove the diaphragm, diaphragm return spring
Recovery Valve Assembly. and O-ring cover and body seals.

Quick Recovery Valve Removal Quick Recovery Valve Assembly

1. Switch battery disconnect off. Block coach and vent 1. Assemble valve in reverse order of Quick Recovery
the entire air system. Valve Disassembly.
2. Disconnect electrical harness from coil assembly. 2. Install the hex nut on top of the coil assembly and
torque to 43-53 in-lbs (4.8-5.8 Nm).
3. Disconnect the quick recovery valve, pressure
switch and plumbing assembly from the Quick Recovery Valve Installation
suspension junction block and leveling valve air 1. Install valve assembly in reverse order of the
lines. removal procedure.

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 12A-7

PRESSURE PROTECTION VALVE 3. Remove inlet valve from stem, spring retainer and
Every 25,000 miles (40,000 km) or 750 operating inlet valve spring.
hours, perform the operational and leakage tests. 4. Turn piston over and depress the inlet valve stem
Every 100,000 miles (160,000 km) or 3600 operating fully and remove the O-ring.
hours disassemble, clean and inspect all parts. Replace 5. Clean and inspect all rubber parts and springs for
all rubber parts and any metal parts showing signs of wear.
wear or deterioration (Figure 1).
Pressure Protection Valve Assembly
Pressure Protection Valve Leakage Test 1. Lubricate all O-rings, O-ring bores and all sliding
1. Block the wheels and fully charge air system before surface with lubrication specification S-25 (Silicon
turning engine off. Fluid - Dow Corning 200).
2. Apply soap solution to the valve cap. Leakage must 2. Reinstall inlet valve stem into piston.
not exceed a one inch bubble in three seconds. 3. Install small O-ring on piston plug and install piston
3. Drain air pressure from the delivery side of valve, plug, pressing snugly into piston body.
disconnect the delivery port line and apply soap 4. Install inlet valve spring, spring retainer and snap on
solution to the delivery port. Leakage must not the rubber inlet valve.
exceed a one inch bubble in five seconds. 5. Install O-ring onto piston end and insert into body.
4. If leakage is excessive, repair or replace the valve. 6. Replace spring and install adjust knob locknut.
Pressure Protection Valve Operational Test 7. Install adjusting knob and adjust the valve before
1. Install a pressure gauge and drain valve on the tightening locknut.
supply and delivery sides of the valve. 8. Test the valve for leakage.
2. Build system air pressure and turn engine off.
Pressure Protection Valve Installation
3. While watching the gauges on both sides, slowly 1. Install pressure protection valve in reverse order of
exhaust air from the delivery side of valve until valve Pressure Protection Valve Removal.
closing pressure is reached.

NOTE: Both sides should show pressure loss until the ADJUSTING NUT
the closing pressure of the valve is reached. Closing
SPRING
pressures should be noted on valve. Opening
pressures are 15-20 psi greater that closing pressure. O-RING
VALVE SPRING
PISTON
Pressure Protection Valve Removal VALVE
1. Switch battery disconnect off. Block coach and vent STAMPED NUT
the entire air system. PISTON PLUG
2. Label and remove all air lines from the valve.
VALVE STEM (1/4” O.D.)
3. Unfasten and remove the valve from the coach.
O-RING
Pressure Protection Valve Disassembly
VALVE GUIDE
1. Loosen locknut from knob and unscrew adjust BODY
knob, then remove locknut. PRESSURE PROTECTION VALVE 6889
2. Remove spring, piston, piston plug and inlet valve
from body. FIGURE 1

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Printed in Canada.
 Date March 2003 Page 12A-8

RELAY VALVE R-12 In-line filters (Figure 2) are found on the supply
Every 25,000 miles (40,000 km) or 750 operating reservoir assembly and may also be installed on the front
hours, perform Relay Valve Operational and Leakage accessory reservoir assembly.
Test. Every 10,000 miles (16,000 km) or 300 operating
Every 100,000 miles (160,000 km) or 3000 operating hours, disassemble, clean and inspect the in-line filters.
hours, disassemble, clean and inspect all parts. Install Replace the elements and o-rings.
new rubber parts and replace worn or damaged parts.
Relay Valve Operational and Leakage Test
1. Block the wheels, charge air brake system and CAUTION
adjust the brakes.
2. Make several brake applications and check for Failure to service the air filters at regular
prompt application and release of brakes at each intervals may affect the operation of other
wheel. components.
3. Check for inlet valve and O-ring leakage by coating
the exhaust port and area around the retaining ring
with soap solution. A one inch bubble in three
seconds is permitted. NOTE: Air filters should be serviced at the beginning
of winter to prevent freezing damage.
NOTE: Make this check on the service R-12 with the
service brakes released.
In-Line Filter Replacement
IN-LINE AIR FILTERS 1. Switch the battery disconnect off. Block the coach
and vent the entire air system.
2. Label and disconnect inlet air fittings and lines.
3. Remove and disassemble the filter housing.
4. Remove the filter element, the spring and the o-ring.
5. Clean the filter housing and threads.
Element 6. Inspect the spring for corrosion and replace if
necessary.
Spring
O-Ring 7. Install a new filter element and o-ring.
IN-LINE AIR FILTER 8. Assemble the filter.
9. Apply thread sealant and install.
FIGURE 2

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Printed in Canada.
 Date March 2003 Page 12A-9

SPECIFICATIONS
LEVELING VALVE
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Barksdale
KNEEL ROCKER SWITCH
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sterling Electronics
KNEELING MODULE
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hypower
KNEEL CUT-OUT PRESSURE SWITCH
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Whitman Controls
Pressure setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 psi
RECOVERY CUT-OUT PRESSURE SWITCH
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Whitman Controls
Pressure setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 psi
TAG UNLOADING VALVE
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Norgren
TAG UNLOAD HOLDING VALVE
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hypower
TAG UNLOAD PRESSURE SWITCH
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Whitman Controls
Pressure setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 psi
TAG UNLOAD ROCKER SWITCH
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Marsh Electronics

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 12B-1

SECTION 12B

FRONT, DRIVE AND TAG AXLE SUSPENSION

CONTENTS OF THIS SECTION
SUBJECT PAGE
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12B-4
Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12B-4
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12B-5
Radius Rods, V-Link and Bushings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12B-5
Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12B-5
Radius Rod Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12B-5
V-Link Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12B-5
Bushing Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12B-6
Radius Rod and V-Link Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12B-6
Air Springs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12B-7
Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12B-7
Removal: Front Axle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12B-7
Removal: Drive and Tag Axles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12B-7
Installation: Front Axle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12B-8
Installation: Drive and Tag Axles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12B-8
Sway Bar: Front and Tag Axles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12B-9
Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12B-9
Link Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12B-9
Link Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12B-9
Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12B-9
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12B-9
Bushing Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12B-9
Shock Absorbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12B-10
Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12B-10
Misting vs Leaking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12B-10
Heat Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12B-10
Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12B-11
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12B-11
Torque Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12B-14
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12B-15

MOTOR COACH INDUSTRIES

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 Date March 2003 Page 12B-2

SHOCK ABSORBER

AIR SPRING

LEVELING VALVE

FRONT AXLE SUSPENSION RADIUS ROD

FIGURE 1

MOTOR COACH INDUSTRIES

Printed in Canada.
Date March 2003 Page 12B-3

DRIVE AXLE SUSPENSION

FIGURE 2

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 12B-4

GENERAL DESCRIPTION lobe. The air springs are a one-piece design with a
snap-on lower piston. The upper plate is mechanically
The front axle is located longitudinally by one leading fastened to the lobe. A bead on the lower portion of the
v-link above and behind the axle, and two trailing radius lobe snaps over a lip on the top of the piston.
rods below and forward of the axle. The front axle is also
located laterally by the v-link, which absorbs side loads All air springs are equipped with rubber spring
generated during cornering. The front axle suspension assisters. On the front axle, the assisters are attached to
has two air springs, one sway bar, two shock absorbers the lower piston, inside the air springs. On the drive and
and one mechanical leveling valve. tag axles, the assisters are on the support structure.
The drive axle is located longitudinally by one upper There are two air springs on the front axle, four on the
v-link and two lower radius rods, all forward of the axle. drive axle and two on the tag axle. On the drive axle, the
The drive axle is also located laterally by the v-link. The air springs are located over the inner wheels, one
drive axle has four air springs, four shock absorbers and forward and one rearward of the axle.
two mechanical leveling valves. In coaches without the tag unload option, the drive
The tag axle is located by one upper v-link and two axle air springs are plumbed in series with the tag axle air
lower radius rods, located forward of the axle. The axle is springs. They receive the same pressure input and,
also located laterally by the v-link. The trailing axle has therefore, are adjusted simultaneously. There is no
two air springs, one sway bar and two shock absorbers. provision for isolating or dumping the tag axle air
Radius rods have replaceable rubber bushings. springs.

COMPONENTS Sway Bars

Also see Section 12A (Suspension Control). Sway bars are used at the front and tag axles to
Radius Rods, V-Link and Bushings reduce body roll during cornering.
Radius rods are mounted at both ends through The front sway bar is mounted to the coach frame
rubber-bushed eye pins. The bar pins are integral to the through compliant bushings and attaches to the axle
bushing, and have a ball joint encased in the rubber. The support structure with sway bar links. (Figure 1)
ends of the bar pins are drilled to accept through bolts The tag axle sway bar is mounted to the axle support
that attach to the coach frame. The bushings are structure with compliant bushings and attaches to the
retained in the eye ring by a shoulder on one side and a frame with solid sway bar links. (FigureNO TAG)
snap ring on the other.
The v-link uses the same bushings at the two body Shock Absorbers
ends of the link, and a larger but similar bushing at the
Shock absorbers absorb energy and dampen the
axle end.
suspension movement. The front and tag axles have two
The drive axle v-link is mounted directly to the top of shock absorbers each, and the drive axle has four shock
the support structure, eliminating the need for a bracket absorbers. Shocks are mounted in rubber eye bushings
on the axle housing. at the upper end and bayonet style rubber biscuits at the
Air Springs lower end.
Air springs support the coach’s vertical load. Air Shock absorbers are not adjustable and cannot be
springs contain pressurized air inside a heavy rubber repaired. Defective shock absorbers must be replaced.

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 12B-5

MAINTENANCE
WARNING
WARNING
Support the axle in at least three places.
Personal injury or component damage can
Do not access suspension components from result if the axle is not properly supported. If
the wheel wells. Unintentional actuation of the possible, remove and replace only one
leveling valves could cause serious injury or suspension link at a time to prevent axle
death. Always block the coach body during movement.
inspection or repair. Block the axle beam
securely before removing suspension links.

RADIUS RODS, V-LINK AND BUSHINGS 4. Remove the radius rod at the axle end. Note the
location of any alignment shims.
Radius Rod, V-Link and Bushing Inspection
Inspect radius rods, v-link and bushings every 50,000
miles (80,000 km). Replace if necessary.
Do not rely on visual inspection to determine
serviceability.
CAUTION
1. Place the coach over a pit, grab the radius rod with
both hands and check for free play. If there is When removing the body end fasteners,
movement of 1/32” (0.8 mm) or more, replace the use extreme caution to avoid damaging
bushings. the threads. They are tapped into the frame
member.
2. Inspect the radius rods for cracks using a magnetic
particle inspection. (i.e. Magnaflux)
3. Ensure that there are no marks that indicate contact
between the eye and pin or between the eye and 5. Remove the radius rod at the body end.
coach frame.
4. Ensure that rubber is not cracked, displaced or
V-Link Removal
deteriorated.
5. Inspect for bent or deformed snap rings or damage 1. Set the park brake and switch the main battery
to the snap ring groove. Replace the entire radius disconnect off.
rod if the snap ring groove is damaged. Replace 2. Elevate and block the coach body. See Section 3
damaged bushings or snap rings. for jacking and support locations.
3. Lift and support the axle so that the v-link arms are
CAUTION parallel to the ground.

Failure to replace worn bushings will

cause excessive wear to tires and other
suspension components. WARNING
Radius Rod Removal Support the axle in at least three places.
1. Set the park brake and switch the main battery Personal injury or component damage can
disconnect off. result if the axle is not properly supported. If
2. Elevate and block the coach body. See Section 3 possible, remove and replace only one
for jacking and support locations. suspension link at a time to prevent axle
movement.
3. Lift and support the axle so that the radius rods are
parallel to the ground.

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 12B-6

4. Loosen the v-link fasteners at the axle end. Do not 6. Insert the spacer (if used) and snap ring into the
remove the axle end from the mount. Leave the tapered sleeve. Ensure that:
fasteners loosely in place. Note the location of any S the snap ring end gap points toward the center of
alignment washers. the radius rod, and
5. Remove the fasteners from the body end of the S the spacer end gap is 180˚ from the snap ring end
v-link. gap.
6. While supporting the v-link, free the body ends and 7. Place the arbor tool into the tapered sleeve over the
swivel the rod upward. snap ring and press into place until the snap ring is
7. While supporting the v-link, remove the fasteners seated in its groove (Figure 3).
from the axle end.
8. Carefully maneuver the v-link out of the axle area
and onto the ground. Take care to avoid damaging BUSHING INSTALLATION
TOOL
other components.
PRESS
Bushing Replacement
Bushing replacement is essentially the same for
radius rods and v-links. Installation/removal tool sets RADIUS ROD
contain the following:
S Receiving Fixture that fits on the press bed and RADIUS ROD BUSHING
supports the link housing,
PIPE STAND
S Tapered Installation Sleeve that compresses the
spacer (if used) and the snap ring,
S Arbor Tool that presses the snap ring and spacer into FIGURE 3
the housing.
8. Remove the tools and check that the snap ring is
CAUTION fully seated all the way around the housing.

Radius Rod and V-Link Installation

Support or block components following
For front suspension components, see Figure 4.
hydraulic press operating procedures.
1. Install radius rods and v-links in the reverse of
Radius Rod Removal and V-Link Removal, noting
1. Note the orientation of the pin mounting holes with
the following:
respect to the radius rod tube.
a. Use extreme caution when starting fasteners
2. Remove the snap ring and spacer (if used), and
into the body mounting plates. The mounting
push out the worm joint. Ensure that the pin, the
holes are tapped into the frame members and
steel outer sleeve and the rubber member are all
must not be cross-threaded.
removed.
3. Clean the housing bore and snap ring groove. b. When starting fasteners, align the bar pin
surfaces to prevent side loading.
4. Insert the new bushing into the housing, ensuring
the proper orientation of the pin mounting holes. c. Replace any alignment shims or washers in their
original locations.
5. Place the receiving fixture onto the press table and
place the rod and bushing onto the fixture. Position 2. Torque fasteners according to the Torque Chart.
the tapered installation sleeve over the rod housing. 3. Check the coach’s alignment.

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 12B-7

5. Inspect the surface of the lower piston for dirt. Clean

SHOCK ABSORBER if necessary, taking care to avoid gouging the
AIR SPRING piston surface.
6. Perform a leak check by spraying soapy water onto
the spring lobe. Pay particular attention where the
SWAY BAR lobe attaches to the piston and the upper plate.
Air Spring Removal: Front Axle
SHOCK

WARNING
Do not work under the coach or near the
wheel well unless the coach body is
securely supported on stands. Do not
remove an air spring unless all air is
V-LINK released from the spring.
RADIUS ROD AXLE
1. Set the park brake.
2. Switch the main battery disconnect off.
FRONT SUSPENSION COMPONENTS 3. Raise the coach to working height and block the
coach body as described in Section 3.
FIGURE 4 4. Remove the wheel to improve working clearance
and block the axle securely.
5. Completely release the air from the air spring by
AIR SPRINGS opening the drain valve on the auxiliary suspension
tank in the front wheel well area.
6. Remove the nuts from the studs on the lower piston.
CAUTION 7. Disconnect the air lines from the upper plate of the
air spring by pushing the collar in toward the fitting
Do not reach into the wheel well or axle area body, then pulling the air line straight out from the
from outside the coach. The suspension may fitting. DO NOT FORCE. If there is resistance,
suddenly move, causing serious injury. release and repeat.
8. Remove the nuts from the studs on the upper plate.
9. Partially collapse the spring lobe over the piston so
that the studs and fittings clear the holes in the
WARNING mounting brackets.
10. Remove the air spring.
Air springs contain compressed air and a Air Spring Removal: Drive and Tag Axles
large amount of energy when inflated. Do
not repair or remove an air spring unless
the air is completely released from the
spring. Use caution when working near an
WARNING
inflated air spring.
Do not work under the coach or near the
wheel well unless the coach body is
Air Spring Inspection securely supported on stands. Do not
1. Switch the main battery disconnect off. remove an air spring unless all air is
released from the spring.
2. Inspect for cracks, cuts, abrasions or irregular wear
patterns. If damage exposes the cords of the lobe, 1. Set the park brake.
replace the air spring. 2. Switch the main battery disconnect off.
3. Inspect for bulges. If found, replace the air spring. 3. Raise the coach to working height and block the
4. Inspect the surface of the lower piston for nicks, coach body as described in Section 3.
sharp edges or corrosion. If sharp edges are found, 4. Remove the wheel to improve working clearance
check the contact point of the lobe for abrasion. and block the axle securely.

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5. Completely release the air from the air spring by NOTE: For the leveling valves to fill the air springs, the
opening the drain valve on the auxiliary suspension axle must be closer to the body than the set ride
tank located in the rear wheel well area behind the height. If necessary, lower the coach onto the spring
tag axle. assisters.
6. Remove the nuts from the studs on the lower piston.
7. Remove the four fasteners that attach the upper
mounting plate to the coach frame. WARNING
8. Separate the plate from the frame. (There may be
sealer between the plate and the frame.) Do not inflate the air springs by disconnecting
9. Lower the air spring and plate assembly to gain the valve linkage and operating the valve
access to the air line fittings. Take care to avoid manually. The air springs fill very quickly,
damaging the air lines. causing the coach to move suddenly. Serious
injury can result.
10. Note the location of each air line.
11. Remove the air lines from the fittings. Air Spring Installation: Drive and Tag Axles
12. Compress the spring slightly to free the studs in 1. Install air springs in the reverse of Air Spring
the lower piston from the support structure. Removal -- Drive and Tag Axles, noting the
13. Remove the air spring and plate assembly. following:
14. Remove the air line fittings from the upper plate to a. Reassemble the fittings in the same positions
separate the air spring from the mounting plate. and orientations as originally installed.
15. Remove the necessary fittings, paying attention to b. Torque fasteners according to the Torque
their location and orientation. Chart.
16. Remove the nuts from the studs on the upper plate c. When installing the air spring/plate assembly,
and separate the spring from the plate. take care not to damage the air lines.
d. If sealer was originally installed on the plate,
Air Spring Installation: Front Axle apply new sealer to the mating surfaces.
1. Install air springs in the reverse of Air Spring
NOTE: For the leveling valves to fill the air springs, the
Removal -- Front Axle, noting:
axle must be closer to the body than the set ride
a. Reassemble the fittings in the same positions height. If necessary, lower the coach onto the spring
and orientations as originally installed. assisters.
b. Torque fasteners according to the Torque
Chart.
c. Ensure that the air lines do not contact any sharp WARNING
edges of the frame or the tire.
d. To connect the air lines, insert the air line straight
Do not inflate the air springs by disconnecting
into the fitting’s collar, then push the air line the valve linkage and operating the sensor
straight into the fitting. A slight resistance will be manually. The air springs fill very quickly,
felt as the air line goes into the fitting, followed by causing the coach to move suddenly. Serious
a hard stop. Tug lightly on the air line to ensure injury can result.
engagement.

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SWAY BAR: FRONT AND TAG AXLES 2. Switch the main battery disconnect off.
3. Raise the coach to working height and block the
coach body as described in Section 3.
SWAY BAR LINK
4. Position the axle so that the link bushings are
relaxed and both wheels are at the same height.
Block the axle at this position.
5. Remove the cotter pins and castle nuts from one
BRACKET
link.
6. Use a puller to remove the link studs from the sway
bar and axle support structure.
7. With the link removed from one side, support the
sway bar to prevent it from dropping and repeat
SWAY BAR BUSHING steps 5 and 6 on the other link.
FRONT SWAY BAR ASSEMBLY
Sway Bar Link Installation
FIGURE 5 1. Install the sway bar link in the reverse of Sway Bar
Link Removal.
2. Torque fasteners according to the Torque Chart.
SWAY BAR BUSHING
Sway Bar Removal
1. Remove the sway bar links as detailed in Sway Bar
Link Removal.

BRACKET WARNING
Take care when removing the sway bar. It may
rotate downward.

2. While supporting the bar, remove the fasteners at

the body mount brackets.
SWAY BAR LINK
3. Maneuver the bar out from the axle area. Take care
TAG SWAY BAR ASSEMBLY to avoid damaging other components.

FIGURE 6 Sway Bar Installation

1. Install sway bar in reverse of Sway Bar Removal.
2. Torque fasteners according to the Torque Chart.
CAUTION Sway Bar Bushing Replacement
Do not reach into the wheel well or axle area 1. Follow steps 1 through 4 of Sway Bar Removal.
from outside the coach. The suspension 2. Remove one bushing bracket.
may move suddenly, causing serious injury. 3. Grasp the bushing with both hands and spread the
backside open. Pull the bushing over the bar.
Sway Bar Inspection 4. Install the new bushing. Replace the bushing
1. Inspect the bushings for wear and deterioration. bracket and install new fasteners.
2. Ensure that all fasteners are tight. 5. Torque fasteners according to the Torque Chart.
3. Inspect for marks indicating contact between the 6. Repeat steps 2 through 5 on the other bushings.
brackets and the mounting crossmember.
4. Inspect the link for wear, deterioration and cracks.
5. Inspect the sway bar for cracks or other damage.
CAUTION
Sway Bar Link Removal Use new fasteners and torque as specified.
1. Set the park brake.

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SHOCK ABSORBERS Misting vs Leaking

Misting is a normal condition. During operation, small
amounts of shock fluid evaporate through the upper seal

WARNING and condense on the outside of the shock body. Road

grime often coats the body of a misting shock.
A leaking shock shows clear signs of fluid leaking in
Do not access suspension components from streams from the upper seal. These streams can be
the wheel wells. Block the coach body and seen best when the shock is fully extended. Inspect as
switch the battery disconnect off. far up the main body as possible. A leaking shock must
be replaced. ( Figure 8)
Shock Absorber Inspection
Inspect shock absorbers every 50,000 miles (80,000
km) or when any suspension components are repaired
or replaced. Also inspect shock absorbers if the coach
has uneven tire wear, ride deterioration or excessive
vibration.

FIGURE 8

Shock Absorber Heat Test

Shock absorbers operate between ambient
temperature and approximately 350_F. A properly
operating shock will be warm or hot to the touch after
normal use.
1. Drive the coach at moderate speeds for 15 minutes.
SHOCK ABSORBER 2. Elevate and block the coach.
INSPECTION 3. Touch the chassis near a shock absorber, then
carefully touch the shock absorber body below the
FIGURE 7 dust cover. The shock absorber should be warmer
than the chassis.
1. Inspect shock mounts.
4. Repeat for all shock absorbers on that axle. All
2. Ensure that fasteners are tight. shock absorbers on one axle should be
3. Inspect shock absorber body for physical damage approximately the same temperature.
or evidence of leakage. (See Figure 7.) 5. Replace any shock absorber that is:
4. Inspect shock absorber rod for bending, nicks, a. the same temperature as the chassis,
scratches or evidence of leakage. A light film of oil b. noticeably cooler than the other shock(s) on the
on the rod is normal. (See Misting vs Leaking.) same axle.
5. Inspect rubber bushings for deterioration. 6. Shake the shock. Metallic rattling indicates internal
6. Road test the coach. failure. Replace the shock.
7. If ride deterioration indicates that a shock has failed 7. Repeat the test for all axles. Different temperatures
internally, perform a Shock Absorber Heat Test. from axle to axle do not indicate failure.

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Shock Absorber Removal 1. Install in the reverse of Shock Absorber Removal,

1. Set the parking brake and block the coach. noting:
2. Run the coach, turn the front wheels to the left (this a. Tighten the upper mounting fastener to pull the
gives more room to work around the shock mounting bracket flanges tight against the sides
absorbers), and shut off the coach. of the upper bushings.
3. Switch the main battery disconnect OFF. b. Install the lower bushings and washers as
4. Remove the rubber cap from the lower attaching nut shown in Figure 9.
and remove the nut, lower washer and lower c. Ensure that the mounting brackets are not
bushing. damaged.
5. Compress the shock absorber slightly by hand and d. Torque upper and lower fasteners to
remove the upper bushing and washer. specification. (See Torque Chart.)
6. Remove the nut from the upper bolt and, while
supporting the shock, remove the bolt.
7. Pull the shock out from the upper bracket.
Shock Absorber Installation

CAUTION
Do not overtighten the lower mounting
nut. The stud on the bottom of the
shock absorber has a shoulder to
prevent over-compression of the
bushings. Over-tightening can break LOWER SHOCK INSTALLATION
the stud, requiring replacement of the
shock absorber. FIGURE 9

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10

13

11

12

FRONT AXLE
TORQUE REFERENCE

FIGURE 10

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10

11 3 12
13

14
9

DRIVE AXLE 1
TORQUE REFERENCE 5

FIGURE 11

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TORQUE CHART (Figures 10 & 11)

Component Key Fastener Axle lb-ft N-m
Suspension Structure 1 Axle Mount Front, Tag 320 434
Drive 220 298
V-Link 2 Body Capscrew All 340 461
3 Axle Hex Nut All 550 746
Radius Rod 4 Body Capscrew Front, Drive 200 271
Body Hex Nut Tag 200 271
Body Jam Nut Tag 100 136
5 Axle Hex Nut All 200 271
Axle Jam Nut All 100 136
Sway Bar 6 Clamp Hex Nut Front, Tag 300 407
Clamp Jam Nut Front, Tag 100 136
7 Link Nut Front, Tag 175 237
Shock Absorber 8 Upper Hex Nut All 160 217
9 Lower Hex Nut All Torque until bushings compress
to 70% of original thickness
Air Spring 10 Upper Hex Nut All 25 34
11 Lower Hex Nut All 50 68
Leveling Valve 12 Mounts Front, Drive 9 12
13 Linkage Front, Drive 17 23
Bump Stop 14 Support Mount Drive, Tag 65 88
n/a Body Mount Drive, Tag 65 88
Tie Rod Lock Plate 15 Clamp Hex Nut Tag 100 136

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SPECIFICATIONS
SUSPENSION AIR SPRING
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Goodyear
Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Rolling Lobe
SWAY BAR ASSEMBLY: FRONT AND TAG AXLES
Make . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hellwig
SHOCK ABSORBERS
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Monroe

MOTOR COACH INDUSTRIES

Printed in Canada.
 6(59,&( %8//(7,16
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 Date March 2003

SECTION 13
TRANSMISSION
A1 -- Transmission Installation: Allison B -- 500 & B -- 500R
A2 -- Transmission Installation: ZF As Tronic (Optional)

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SECTION 13A1

AUTOMATIC TRANSMISSION
ALLISON B-500 & B-500R
CONTENTS OF THIS SECTION

SUBJECT PAGE
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13A1-2
Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13A1-2
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13A1-3
Periodic Inspections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13A1-3
Lubrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13A1-3
Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13A1-7
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13A1-7
Torque Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13A1-8
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13A1-8

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GENERAL DESCRIPTION Vehicle Interface Module (VIM)

The vehicle interface module connects the WTEC to
the coach. It is located in the upper right corner of the
Coaches are equipped with Allison B-500 or B-500R
battery compartment beside the control module. The
six-speed (WTEC) electronically-controlled automatic
VIM has the following input/output connections:
transmissions.
1. Battery
The transmissions typically have a remote mounted 2. Ignition sense voltage
oil cooler assembly, the (WTEC) Electronic Control
3. Reverse warning
System, lockup torque converter assembly with torsion
dampening, and a triple planetary gear setup. 4. Speedometer
5. Dimmer
B-500(R) transmissions also have internal filtration
6. Neutral shift
systems and combination control module and sump
cover assemblies. The B-500R transmissions have an 7. Do not shift
output retarder assembly and an accumulator circuit. 8. Chassis ground (EMI)
9. PTO enable switch
For detailed service procedures for Allison automatic
transmissions, see the applicable Allison Transmission 10. PTO engage signal.
Service Manuals. Torque Converter
The torque converter consists of three elements: the
pump, the turbine and the stator assemblies. The pump
COMPONENTS is the input element, driven directly from the engine. The
turbine is the output element and is hydraulically driven
by the pump. The stator is a reaction (torque multiplying)
Electronic Control System element.
The (WTEC) Electronic Control System is five major When the pump turns faster than the turbine, the
components connected by a wiring harness. These converter multiplies torque. When the turbine
components are the Electronic Control Unit (ECU), approaches the pump speed, the stator starts to rotate
engine throttle position sensor (TPS), three speed with the pump and turbine. When this occurs, torque
sensors, the shift selector, and the control module multiplication stops and the converter functions as a
(which contains the solenoid valves and pressure fluid coupling.
switch). The lockup clutch is inside the torque converter. It has
The throttle position sensor, speed sensors, pressure three elements: the piston, clutch plate/damper and
switch, and shift selector transmit information to the back plate. The piston and back plate are driven by the
ECU. The ECU processes this information and sends engine. The clutch plate/damper, located between the
signals to actuate specific solenoids on the transmission piston and the back plate, is splined to the converter
control module. These solenoids control both the turbine. The lockup clutch engages and releases in
application and release of hydraulic clutch pressures response to electronic commands from the ECU.
during a shift function. Lockup clutch engagement provides a direct drive from
the engine to the transmission gearing. This eliminates
A feature of the WTEC control system is the ability to converter slippage, maximizing fuel economy. The
adapt or “learn” as it operates. Each shift is used by the torsional dampening feature absorbs engine vibration.
ECU to optimize shifting points and clutch application.
Planetary Gears & Clutches
A series of three planetary gear sets and shafts
Note: If the shift quality of a low-mileage coach or provide the gear ratios and direction of travel for the
coach with a new or recalibrated ECU is coach. The planetary gear sets are controlled by five
unacceptable, simply drive the coach through its multi-plate clutches. These clutches work in pairs to
normal shift ranges a few times. After a short learning produce the six speeds. The clutches apply and release
period, any rough shifting should be corrected and hydraulically in response to electronic ECU signals to
the shift quality restored. the appropriate combination of clutch solenoids.

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Retarder (Optional) MAINTENANCE

The self-contained retarder assembly is at the output
shaft end. It consists of a vaned rotor which rotates in a PERIODIC INSPECTIONS
vaned cavity. Applying the retarder instantly releases Clean and inspect the exterior of the transmission at
fluid to a control valve to fill the cavity. The rotating regular intervals. Severity of the service conditions will
element acts to slow the coach quickly without determine the frequency of these inspections. Some of
excessive wear to the brakes. the more common inspections would focus on the
following conditions:
Cooler Circuit a. Check for loose fasteners on the transmission and
The transmission fluid is cooled by a remote-mounted mounting components every 50,000 miles.
fluid cooler. The cooler is a liquid-to-liquid heat b. Improper fluid levels or fluid leaks,
exchanger that uses engine coolant to reduce the c. Damaged or loose cooler hoses,
transmission fluid temperature. d. Worn or improperly routed electrical harnesses,
e. Loose, dirty, or improperly adjusted throttle position
Shift Selector (WTEC Control) sensor.
The electronic shifting is totally automatic. The shift
range selections are made through a touch-pad module LUBRICATION
on the driver’s left-hand console. (Figure 1). The transmission fluid lubricates and transmits
hydraulic power. Always maintain proper fluid levels. If
fluid level is too low, the torque converter and clutches
do not receive enough fluid, and the transmission
overheats. If the level is too high, the fluid aerates,
causing the transmission to shift erratically and
DIGITAL DISPLAY
overheat. Fluid may be expelled through the breather or
dipstick tube when the fluid level is too high.
MODE ID Check the transmission fluid level daily, with the
manual cold-check procedure. Check the hot
MODE ON INDICATOR transmission fluid level, preferably electronically. Check
the fluid level using the following procedures and record
MODE BUTTON them in a maintenance log.

WARNING
When manually checking the fluid level, be
sure the transmission is in neutral, the park
brake is applied and the wheels are blocked.
Sudden vehicle movement may occur if
these precautions are not taken.
FIGURE 1

Manual Cold Fluid Level Check (with dipstick)

The purpose of the cold check is to determine if the
NOTE: The transmission has a hold feature to transmission has enough fluid for safe operation until a
prohibit upshifting above the range selected during hot check can be made. Always check the fluid level
normal driving. For downhill operation, however, the twice.
transmission may upshift above the highest selected 1. Park vehicle on a level surface.
range when engine-governed speed is exceeded and 2. Clean all dirt from around the end of the fluid fill tube
damaging engine over-speed is a possibility. before removing the dipstick.

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3. Perform the following: NOTE: Consistency is important to maintain reading

a. Run the engine for at least one minute. accuracy in a manually checked level. If inconsistent
readings persist, check the transmission breather to
b. Apply the service brakes, shift transmission to be sure it is clean and unclogged.
drive (D) and operate the engine at 1000 -1500
rpm for 30 seconds.
c. Shift to reverse (R) to clear the hydraulic system Electronic Fluid Check
of air. 1. After reaching the normal operating temperature,
d. Shift into neutral (N) and allow the engine to idle park the vehicle on a level surface and allow the
(500-800 rpm). engine to idle (500-800 rpm).
4. With engine idling, remove the dipstick from the
tube and wipe it clean. NOTE: The oil level sensor’s temperature range is
from 140-220_F (60-104_C).
5. Insert the dipstick into the tube and remove it.
Check the fluid level.
2. Simultaneously press the Y “UP” and B “DOWN”
6. Wipe the dipstick and repeat step 5 to verify the fluid
arrow buttons once.
level.
7. If the fluid level is within the “COLD RUN” band on The ECU may delay the fluid level check until:
the dipstick, the transmission may be operated until
the fluid is hot enough to perform a “HOT RUN”
check. If the fluid level is not within the band limits, a. Transmission fluid temperature is above 140_F or
add fluid as necessary to bring the level to the below 220_F.
middle of the band. b. The transmission is in neutral (N).
8. Perform a hot check at the first opportunity after the c. The vehicle has been stationary for five minutes to
normal operating temperature is reached. allow the fluid to settle.
d. The engine is at idle speed.
Manual Hot Fluid Level Check
1. Operate the transmission in drive until the normal A delayed fluid level display signal is a flashing
operating temperature is reached. indicator under the SELECT display and a countdown
from 8 to 1 under the MONITOR display.
NOTE: The normal operating sump temperature is in
the 160-200_F (71-93_C) range. The normal 3. The fluid level will display:
operating converter-out temperature should be in the If correct, OL-OK.
180-220_F (82-104_C) range.
If low, OL-LO-# (number of quarts of transmission
fluid required). eg OL-LO-02 means 2 quarts low.
2. Park the vehicle on a level surface, and allow the
If high, OL-HI-# (number of quarts overfilled). eg
engine to idle (500-800 rpm).
OL-HI-01 means 1 quart overfilled.
3. Clean all dirt from the end of the fluid fill tube. 4. Confirm with a manual fluid level check.
4. Remove the dipstick and wipe it clean.
5. Insert the dipstick into the tube and remove it. NOTE: The dipstick check may not agree exactly
Check the fluid level. with sensor checks, because the oil level sensor
compensates for fluid temperatures.
6. Wipe the dipstick and repeat step 5 to verify the
reading.
7. If the fluid level is not within the limits of the “HOT
RUN” band, add fluid as necessary to bring the
reading to the middle of the band. CAUTION
NOTE: Do not allow dirt or foreign matter to enter the Low or high fluid levels cause overheating and
irregular shift patterns. If not corrected, this
transmission. Dirt or foreign matter in the hydraulic
condition can damage the transmission.
system may cause undue wear of internal
components.

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5. Invalid conditions are reported displayed as OL

followed by “--” and a number. The displayed
number is a code.
CAUTION
NOTE: Invalid conditions include the inability to Prevent contamination of the transmission
check fluid level and system malfunctions. fluid by using clean containers and funnels,
and by keeping the dipstick clean. NEVER
use containers that have been used for
CODE DESCRIPTION engine coolant.

OL -- 50 - Engine speed (rpm) too low.

OL -- 59 - Engine speed (rpm) too high. NOTE: Even small amounts of engine coolant in
transmissions can cause clutch plates to fail.
OL -- 65 - Neutral (N) must be selected.
OL -- 70 - Sump oil temperature too low. Initial Service Interval - Dexron III
OL -- 79 - Sump oil temperature too high. After the first 5,000 miles (8,000 km), change the
transmission fluid and filters. Use lubrication
OL -- 89 - Output shaft rotation. specification S-15 (Automatic Transmission Fluid
OL -- 95 - Sensor failure. DEXRON III) as in Section 10.
6. To exit the oil level display mode, press the neutral Initial Service Interval - TranSynd
button on the selector. Change the transmission filter at 5,000 miles (200
hours), 25,000 miles (1,000 hours) and 50,000 miles
Fluid Specification (2,000 hours.)
All fluids must meet Allison’s Type C-4 specification. Change the transmission fluid at 50,000 miles (2,000
DEXRON III fluids are recommended for most coach hours) and 100,000 miles (4,000 hours). Use lubrication
automatic transmission service conditions. Allison specification S-15A (TranSynd automatic transmission
TranSynd is a synthetic transmission fluid specified fluid) as shown in Section 10 of this manual.
under certain transmission warranties.
Periodic Service Interval - Dexron III
Coaches with the Allison Extended Warranty must Every 25,000 miles (40,000 km) or 18 months, change
use TranSynd automatic transmission fluid. (See the fluid and filters. Use lubrication specification S-15
Section 10.) (automatic transmission fluid DEXRON III) as in Section
10.
The B-500R WTEC transmissions incorporate twin
CAUTION internal (sump-mounted) filters. The filter assemblies are
removed from the bottom.
Extended transmission warranties specify a Periodic Service Interval - TranSynd
different transmission fluid and service Change the transmission filter every 50,000 miles.
intervals. Failure to follow these specifications Change the transmission fluid every 100,000 miles. Use
will void the transmission warranty.
lubrication specification S-15A (TranSynd automatic
transmission fluid) as shown in Section 10 of this
manual.
The minimum safe operating temperature of
DEXRON III is -17_F. Preheat the fluid by idling the coach NOTE: Transmission warranties may specify a
with the transmission in neutral for approximately 20 different service interval. Failure to follow the specified
minutes before driving. service interval will void the warranty.

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Filter Removal Filter Installation

1. Turn the master switch off, and block the front and 1. Pre-lube and install O-rings on the filter elements.
rear wheels. 2. Install the gasket seal on each cover, then join the
2. Remove the drain plug from the control module filter elements onto cover assemblies.
sump, and completely drain the fluid. 3. Install filter and cover assemblies into the control
module filter compartments. Align each filter/cover
assembly with the holes in the channel plate/sump.
NOTE: It is not necessary to drain the fluid if only the Push the cover assemblies in by hand to seat the
filters are to be replaced. The control module and seals.
sump are assembled together.

3. Remove the capscrews from both filter covers. CAUTION

4. Remove the covers, O-rings, gaskets and filter
elements.
Do not use the bolts to draw filter covers to
the sump. This can damage the covers, seals
and/or sump.

4. Install the cover capscrews and torque to 38-45

ft-lbs (51-61 N·m).
5. Inspect the drain plug O-ring and reinstall it into the
control module sump. Torque the plug to 18-24
ft-lbs (25-32 N·m).
6. Refill the transmission and manually check the fluid
level.
NOTE: The amount of refill fluid will be less than the
amount used for the initial factory fill. Some fluid will
remain in the external cooler circuits, torque converter
and transmission cavities after draining. Refer to the
INTERNAL FILTERS C0323 capacity schedule in specifications portion of this
section for exact fluid quantities used in the
FIGURE 2
transmission.

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REMOVAL slide the transmission out and away from engine

while maintaining their alignment.
NOTE: Use a suitable sling, transmission jack or dolly
for Step 8 of this removal procedure. A transmission
dolly is available through parts outlets or may be
fabricated.
CAUTION
1. Place the battery disconnect switch “Off”. Apply the Maintain proper engine-to-transmission
parking brake and block the vehicle wheels. alignment while removing transmission to
2. Disconnect the driveshaft from the transmission. prevent torque converter and input shaft
See Driveshaft Removal in Section 14. binding. Do not allow the rear of the
transmission to fall and hang unsupported
3. Remove the engine and transmission module as an in the splined hubs of the torque converter.
assembly. See Engine Removal in Section 8. Failure to observe this caution will result in
4. Drain the transmission fluid and remove the dipstick damage to the transmission or torque
and fill tube. converter.
5. Disconnect all electrical harnesses and retarder air
lines from the transmission.
6. Disconnect the remote cooler lines from the NOTE: Inspect the engine-to-transmission mounting
transmission. surfaces and flex plates for any signs of wear or
damage.
7. Support the rear of the engine with jack stands.
Remove the mounts and brackets attaching the
transmission to the engine cradle. INSTALLATION
8. Remove the mounting capscrews attaching the 1. Install the transmission in the reverse order of
transmission to the engine flywheel housing and Removal.

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TORQUE CHART
Transmission Hydraulic Line Fittings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40-50 ft-lbs (53-66 N·m)
Transmission Flange Mounting Capscrews (7/16”-14) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 ft-lbs (80 N·m)
Transmission Mounting Bracket Capscrews . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200 ft-lbs (265 N·m)
Flexplate-to-Crankshaft Mounting Capscrews . . . . . . . . . . . . . . . . . . . . . . . . 50 ft-lbs (66 N·m) plus 120 degrees
Flexplate-to-Converter Mounting Capscrews . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-21 ft-lbs (23-28 N·m)

SPECIFICATIONS

TRANSMISSION ASSEMBLY - B500R

Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Allison

TRANSMISSION ASSEMBLY - B500

Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Allison

COOLER ASSEMBLY
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stewart-Warner

ACCUMULATOR ASSEMBLY
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Allison

CAPACITY SCHEDULE
B-500R Initial Factory Fill: 40 Qts. (38 L) Service Fill: 25 Qts. (23 L)
Note: Capacities are approximate only. Note: Capacities shown are for
Please check dipstick levels with the 4-1/2” deep oil pan.
proper “Fluid Level Check” procedure.

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 Date March 2003 Page 13A2-1

SECTION 13A2

ZF AS-TRONICS TRANSMISSION
(OPTIONAL)
CONTENTS OF THIS SECTION

SUBJECT PAGE
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13A2-2
Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13A2-2
Function And Error Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13A-2
Transmission Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13A-2
Lubrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13A-2
System Error Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13A-2

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GENERAL DESCRIPTION CLUTCH ACTUATOR

The ZF AS-Tronic transmission is an Automated The clutch actuator is flange-mounted to the clutch bell
Manual Transmission which has 10 forward gears and a housing of the transmission. The clutch actuator is
dry clutch. There is no clutch pedal in the driver’s area, controlled in an electro-pneumatic manner and is
and the driver has no direct control over the clutch responsible for the entire clutch actuation process. The
engagement for 95% of the vehicle’s operation, the clutch is actuated by the clutch actuator, which in turn is
transmission will react just like a conventional torque activated by the electronics in the transmission actuator.
converter automatic. The transmission can make fully The clutch actuator calibrates the current clutch
automatic shifts or gear shifts can be manually selected. engagement point for every start procedure and passes
Automatic and manual shift range selections are made this information on to the transmission Electronics. The
on the touch-pad on the left side console. electronics therefore always have information on the
current wear status and the friction lining. The driver is
The ZF AS-Tronics consists of a basic transmission
warned in good time of complete clutch wear.
and an integrated splitter and planetary group. The
transmission system performs gear shifts automatically. SHIFT SELECTOR AND DIGITAL DISPLAY
The shift selector contains 6 touch--pad buttons and a
digital display. The buttons select the type of transmission
COMPONENTS operation; the display shows operating and error codes.
TRANSMISSION ACTUATOR Shift Selection Controls ZF
All functions required for transmission The D, N and R shift selection touch--pad buttons each
control/feedback are contained within the transmission have an LED. The LED lights on the key for the selected
actuator (shift module). The transmission actuator transmission operation.
consists of the transmission electronics, shift valves, shift The LED glows steadily when shift range selection is
cylinders and sensors. The actuator has a mechanical, made and the transmission is operating in the selected
electrical and pneumatic interface and is integrated in the shift range.
transmission housing. The individual components are The LED flashes when another shift range selection is
connected electrically and pneumatically within the required, or when the shift range is not completely
transmission actuator. The gear shift cylinders are engage.
integrated into the transmission actuator and are D -- DRIVE is used for normal driving. All shifting is
pneumatically actuated. automatic.
The transmission electronics process all incoming N -- NEUTRAL
signals and initiate the gear shift via solenoid valves and R -- REVERSE
shift cylinders. (See figure 3). Y B-- Used to select gear ranges manually. The
display will show the current gear range. Lower gears
should be selected to provide maximum engine braking
on steep grades.
Fn -- Switches back and forth between automatic
function and manual shifting. If automatic function is
chosen, two horizontal bars between arrows show next to
the gear range number. If only the gear range number
shows, manual gear range selection is indicated.

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SHIFT CYLINDER FOR RANGE

CHANGE GROUP
SHIFT MODULE

SHIFT CYLINDER
FOR MAIN
TRANSMISSION
SECTION
SELECTOR CYLINDER FOR
MAIN TRANSMISSION SECTION

10 GANG

GV
2/3
1/R

GP
SHIFT CYLINDER FOR
SPLITTER GROUP

Figure 3. Transmission Actuator (Shift Module)

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FUNCTION AND ERROR DISPLAYS ZF Engine idle speed required by lifting

Various digital codes are shown in the display. Some of the accelerator pedal. If the code
does not go out, there is a system er-
these are transmission operating status codes and some ror. Safely stop and park the coach
are error codes warning of potentially harmful situations. and call dispatch for help.

The clutch is overloaded. This code

DIGITAL DISPLAY alternates with the normal operating
display.

Clutch wear. Servicing is required.

MANUAL SHIFT
LEDs (UP --- DOWN)
(SHIFT
SELECT
BUTTONS)
A major transmission system failure.
Safely stop and park the coach. Shut
the engine down and call dispatch for
help.
(AUTO/MANUAL
MANUAL/AUTO)
MODE BUTTON

CAUTION

Figure 4. Touch-Pad Shift/Display Module The transmission may upshift to a higher gear
range if damage due to engine overspeed is
possible.
Automatic shift mode selected. Indi-
cated by horizontal bars between ar-
rows next to the selected gear range.

CAUTION
Manual shift mode selected. no hori-
zontal bars between arrows next to
the selected gear range. There is no PARK position on the
transmission touch-pad. Select N (neutral)
and apply the parking brake.
Transmission self ---diagnostic check
which occurs when the ignition switch When shifting from drive to reverse or reverse
is turned on. to drive, stop the coach. With the service
brakes applied, select neutral first, then either
drive or reverse.
Insufficient air pressure to operate the
shifting system. This code alternates The engine must be at normal idle before
with the normal display. Wait until air shifting. If the coach is at fast idle, turn fast
system builds to working pressure idle off and wait for the idle speed to slow
before shifting. before shifting.

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 Date March 2003 Page 13A2-5

Electronic Control System NOTE: If the coach rolls forward in N neutral, pushing
The ZF transmission electronic control system the D touch---pad button automatically selects the
controls the transmission and responds to faults and gear range to match roadspeed and engine R.P.M.
unsafe conditions. These controls work in conjunction With the transmission and engine coupled, the
with the engine control system. engine Jake brake will be operative, if activated.

TRANSMISSION OPERATION CAUTION

STARTING THE ENGINE
The Jake brake, if activated, is inoperative
Refer to “Engine Operation, Fuel And Exhaust” in this
until shifting sequences are completed. The
MCI Operator’s manual for the engine starting and transmission shifts back into automatic mode
stopping procedure. to provide maximum engine braking.
1. When the engine starts, the transmission
Low Speed (Maneuvering) Operation
performs a system diagnostic check. The CH code shows
in the shift selector display. A low speed operating mode (maneuvering) provides
1st. gear for extremely low speed operation. In this mode
2. When the system diagnostics is complete, the N the accelerator pedal is very responsive to position.
code appears in the display. The N LED lights, indicating
Neutral is selected.

Stopping The Engine CAUTION

Follow the procedure in the MCI Operator’s manual for
stopping the engine.
A sudden increase in road speed may occur
1. Park the coach and apply the parking brake. when the transmission system changes to a
2. Push the N (neutral) touch--pad. The N LED will driving gear range.
lights and the N code appears in the display. Downshifting
The driver can downshift for engine braking on
NOTE: The transmission automatically shifts into inclines.
neutral if N range is not selected before stopping the
engine. NOTE: Downshifting will not occur until the coach
has slowed sufficiently to shift without transmission
damage.
Automatic shifting
1. Select D for automatic gear range shifting. The D Manual Shifting
touch–pad LED will light, showing that this function is 1. Manually select gear ranges by pushing the Fn
selected. touch--pad button to switch between automatic D and
2. The automatic shift symbol, up / down arrows with manual “up” / “down” arrow selections.
horizontal bars, and the gear range selected by the NOTE: The automatic shift symbol, up / down arrows
transmission will show in the display. with horizontal bars does not show in the display
3. The automatically selected gear range showing in during manual shifting. Only the manually selected
the display can be changed by pushing the “up” or “down” gear range will show in the display.
touch--pad buttons to select a higher or lower gear range.
The selected gear will show in the display. 2. Manually select gear ranges by pushing the “up”
or “down” touch--pad buttons to select a higher or lower
4. The position of the accelerator must not be
gear range. The selected gear will show in the display.
changed during the shift process. The clutch is actuated
via the electronic transmission control depending on NOTE: If a gear is not selected manually after
accelerator actuation. During the shift, the engine is approximately 10 – 20 seconds, the transmission
influenced by the electronic transmission control. moves back to automatic shift mode.

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CAUTION CAUTION
The driver must avoid over-revving the engine.
The engine may stall if the accelerator is
depressed in too high of a gear. If the coach is moving when attempting to shift
Manual Gear Advancing into or from R reverse, the transmission will
automatically shift into N neutral.
One or two gear ranges can be skipped or advanced by
pushing the “up” / “down” arrows.
The LED on the R touch–pad key will flash until the
1. Push the “up” / “down” arrow twice in rapid transmission selects reverse gear.
succession to advance one gear range over or under the
one shown in the display.
2. Push the arrow button three times in rapid
succession to advance two gear ranges over or under the
selected gear shown in the display.
WARNING
NOTE: The transmission will not make a gear range
selection if it will cause the engine to over---speed.
Clutch Overload Display
The code CL shows in the display if the system senses The engine cannot be switched off if a gear is
the potential of clutch overload. This usually results from selected. The coach may roll away if brakes are
not actuated.
low road speed and low engine rpm with too high a gear
range selected.
1. Lessen clutch wear by starting off and smoothly
accelerating in the lowest possible gear range. COLD WEATHER OPERATION
2. Select a gear range to match road speed and
engine R.P.M. The transmission is filled with gear oil meeting
3. Select N neutral on the touch--pad if the coach will viscosity specifications listed in the ZF lubricant list
be stopped with the engine running for long periods. This TE-ML 02, Lubricant Class 02L. These gear oils can
lessens stress on the clutch. operate in cold temperatures down to --22 degrees
Fahrenheit (--30 degrees C).
Reverse Gear Shifting
The coach must be stopped to shift into R reverse gear When the temperature is between --4 and --22 degrees
from a forward gear range or from R reverse gear into a Fahrenheit ( --20 and --30 degrees C), the transmission
forward gear range. requires approximately a ten minute warm-up.
The LED on the R touch–pad key will light when the Follow the procedure in “Engine Operation, Fuel And
transmission has selected reverse gear. Exhaust” in this G4500 Operator’s manual for starting the
engine.

CAUTION Run the engine until the transmission is warmed up

enough to operate.

When shifting from drive to reverse or reverse If the temperature is below --22 degrees Fahrenheit
to drive, stop the coach. With the service (--30 degrees C), the transmission must be externally
brakes applied, select neutral first, then either heated to above --22 degrees Fahrenheit (--30 degrees C)
drive or reverse. before starting the engine.: Transmission

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EASY START SYSTEM LUBRICATION

The coach is equipped with the “Easy Start System”.
his system operates as follows: TRANSMISSION OIL CHECKS
The transmission is factory filled with gear oil meeting
viscosity specifications listed in the ZF lubricant list
S If the coach is at a stand still,
TE-ML 02, Lubricant Class 02L. Oil change intervals is
185,000 miles or 2 years. There are no serviceable filters
S And the transmission is not in neutral, to change.
NOTE: The clutch does not require preventative
S And the brake pedal is pressed, maintenance. Refer to the proper ZF publications for
the disassembly and repair of the ZF AS-Troncis
S Then the maximum applied brake pressure will be transmission.
held in the brake system after the brake pedal has
been released until:
The clutch is reapplied (via depressing the SYSTEM ERROR CODES ZF
accelerator pedal).
Or for a maximum of 2 seconds after the brake CLEARING AN ERROR CODE
pedal has been released (2 second time-out). Error messages and the resulting actions can be
cleared from the system.
When on steep grades, after coming to a complete
stop, it is recommended to give the brake pedal a heavy 1. Stop the coach and turn the ignition off. The error
apply to insure that enough pressure is held in the brake code display should go out.
line. The driver may then return the brake pedal to a 2. If it is still displayed, turn off the main battery
comfortable position. As long as the brake lights are disconnect switch.
activated, the Easy Start System will remain active. (See 3. Switch the ignition on. If the error code is still
figure 5). displayed, do not operate the coach.

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 Solenoid Valve
Date

System Voltage

Pressure Switch 2 Pressure Switch 1

(Feedback) (Brake--Light)
Brake Air-- Storage
March 2003

Digital
Digital
Brake Pedal

input

output
Page

Check Valve ConventionalSystem

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ASTRONIC Easy Start add--on

Figure 5. Easy Start System

Transmission
13A2-8

controller CAN--Link Engine

Controller

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 Date March 2003 Page 13A2-9

ZF AS-TRONICS DIAGNOSTIC CODES

CODE FAILURE # FAULT

14 22 Short circuit to ground at output ADVP (wakeup control signal for E--module, voltage sup-
ply to display, warning lamp, warning buzzer, output speed sensor 1)
54 Interruption at output ADVP (wakeup control signal for E--module, voltage supply to dis-
play, warning lamp, warning buzzer, output speed sensor 1)
86 Short circuit to positive at output ADVP (wakeup control signal for E--module, voltage sup-
ply to display, warning lamp, warning buzzer, output speed sensor 1)
15 127 Error on ECU temperature sensor signal
193 ECU temperature too high
1F 137 No range change group (GP) sensor signal (Short circuit to positive)
138 No range change group (GP) sensor signal (Short circuit to ground)
139 No range change group (GP) sensor signal (Interruption)
140 Self adjustment error of range change group sensor in position fast
159 Range--change group sensor signal leaves engaged position during driving
20 141 No splitter group (GV) sensor signal (Short circuit to positive)
142 No splitter group (GV) sensor signal (Short circuit to ground)
143 No splitter group (GV) sensor signal (Interruption)
144 Splitter group (GV) sensor self adjustment error
160 Splitter sensor signal leaves engaged position during driving
21 107 Stabilized voltage supply at output AU (clutch sensor supply) out of valid range
117 Error in clutch self--adjustment process
124 Error on clutch travel signal
22 18 Short circuit to ground at output stage to Y17 (valve clutch disengage slow)
19 Short circuit to ground at output stage to Y15 (valve clutch engage slow)
20 Short circuit to ground at output stage to Y16 (valve clutch disengage fast)
21 Short circuit to ground at output stage to Y14 (valve clutch engage fast)
50 Interruption at output stage valve Y17 (clutch disengage slow)
51 Interruption at output stage valve Y15 (clutch engage slow)
52 Interruption at output stage valve Y16 (clutch disengage fast)
53 Interruption at output stage to large Y14 (clutch engage fast)
82 Short circuit to positive at output stage to valve Y17 (clutch disengage slow)
83 Short circuit to positive at output stage to valve Y15 (clutch engage slow)
84 Short circuit to positive at output stage to valve Y16 (clutch disengage fast)
85 Short circuit to positive at output stage to valve Y14 (clutch engage fast)
120 Mechanical failure of small disengagement clutch valve
121 Mechanical failure of large disengagement clutch valve
122 Mechanical failure of small engagement clutch valve
123 Mechanical failure of large engagement clutch valve

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CODE FAILURE # FAULT

23 9 Short circuit to ground at output stage to Y9 (Valve Range)
41 Interruption at output stage to Y9 (Valve Range)
73 Short circuit to positive at output stage to Y9 (Valve range high)
24 8 Short circuit to ground at output stage to Y8 (Valve Range)
40 Interruption at output stage to Y8(Valve Range)
72 Short circuit to positive at output stage to Y8 (Valve range low)
25 2 Short circuit to ground at output stage to Y2 (Valve Splitter; DD: high, OD: low)
34 Interruption at output stage to Y2 (Valve Splitter)
66 Short circuit to positive at output stage to Y2 (Valve Splitter)
26 3 Short circuit to ground at output stage to Y3 (Valve Splitter; DD: low, OD: high)
35 Interruption at output stage to Y3 (Valve Splitter)
67 Short circuit to positive at output stage to Y3 (Valve Splitter)
27 4 Short circuit to ground at output stage to Y4 (Valve Select)
36 Interruption at output stage to Y4 (Valve Select)
68 Short circuit to positive at output stage to Y4 (Valve Select)
28 6 Short circuit to ground at output stage to Y6 (Valve Shift)
38 Interruption at output stage to Y6 (Valve Shift)
70 Short circuit to positive at output stage to Y6 (Valve Shift)
2B 175 Error on “Ignition lock” signal (Key 15)
30 129 No shift sensor signal (Short circuit to positive)
130 No shift sensor signal (Short circuit to ground)
131 No shift sensor signal (Interruption)
132 Self adjustment error of shift sensor
158 Shift sensor signal leaves engaged position during driving
32 5 Short circuit to ground at output stage to Y5 (Valve Select)
37 Interruption at output stage to Y5 (Valve Select)
69 Short circuit to positive at output stage to Y5 (Valve Select)
33 7 Short circuit to ground at output stage to Y7 (Valve Shift)
39 Interruption at output stage to Y7 (Valve Shift)
71 Short circuit to positive at output stage to Y7 (Valve Shift)
36 17 Short circuit to ground at output stage to Y1 (inertia brake valve)
49 Interruption at output stage to Y1 (inertia brake valve)
81 Short circuit to positive at output stage to Y1 (inertia brake valve)
37 118 Clutch does not disengage
119 Clutch does not engage / does not transmit engine torque

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CODE FAILURE # FAULT

38 145 Range change group (GP) disengagement error
146 Changeover error during range change group (GP) shifting
147 Range change group (GP) does not engage
39 108 Error in selector lever or tip lever
110 ZF CAN timeout
3A 154 Main transmission gear does not disengage
155 Main transmission gear does not engage
156 Wrong gear shifting
3B 151 Selector cylinder does not disengage
152 Change over error during gate selection procedure
153 Selector cylinder does not engage
3C 133 No gate select sensor signal (Short circuit to positive)
134 No gate select sensor signal (Short circuit to ground)
135 No gate select sensor signal (Interruption)
136 Gate select sensor self adjustment error
3D 148 Splitter (GV) does not disengage
149 Change over error during splitter shifting
150 Splitter (GV) does not engage
3F 100 Error on output speed signal 2
6A 126 Error on pressure sensor signal
8 161 Easy Start feedback signal permanently active or brake not completely open
162 Easy Start not available
97 102 Plausibility error between transmission input speed and out--put speed
98 10 Short circuit to ground at output stage to Y10 (Main valve)
42 Interruption at output stage to Y10 (Main valve)
74 Short circuit to positive at output stage to Y10 (Main valve)
9A 101 Error on both output speed signals
A1 98 Error on transmission input speed signal
B1 128 Error on oil temperature sensor signal
BF 99 Error on output speed signal 1
194 Both sources for front axle speed not available
E6 166 Permanent idle signal
168 ”No idle signal or error on “idle signal switch” signal (EEC2) or never active ””idle signal”””

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CODE FAILURE # FAULT

E7 26 CAN engine configuration timeout
27 Error on “engine configuration message” (engine configuration)
31 Error on “Actual engine retarder -- percent torque” signal (ERC1_ER)
32 Error on “Engine retarder configuration message” (Engine retarder configuration)
33 CAN “Engine retarder configuration” timeout
91 CAN EBC1 timeout
92 Error on “ABS active” signal (EBC1)
93 Error on “ASR engine control active” signal (EBC1)
94 Error on “ASR brake control active” signal (EBC1)
95 Error on “Cruise control active” signal (CCVS)
97 Error on “Engine speed” signal (EEC1)
163 Engine does not react on torque intervention
164 Error on “Drivers demand engine percent torque” (EEC1)
165 Error on “Accelerator pedal position” (EEC2)
171 Error on “Actual engine percent torque” signal (EEC1)
E7 173 Error on “Brake switch” signal (CCVS)
177 System--CAN Bus off error
178 CAN Error warning
179 CAN queue overrun
180 CAN EEC1 timeout
181 CAN EEC2 timeout
182 CAN CCVS timeout
183 CAN ERC1_ER timeout
197 ”Error on ””Front axle speed”” (WSI)”
198 ”Error on ””Relative wheel speeds”” (WSI)”
199 CAN WSI timeout
F8 25 Short circuit to ground at output SD to display
89 Short circuit to positive at output SD to display
FB 104 High voltage (Vehicle electrical system voltage too high)
105 Low voltage (Vehicle electrical system voltage too low)
FD 190 EOL EEPROM parameter out of valid range
191 EOL EEPROM parameter checksum error
FE 90 Communication error between controller 1 and controller 2 (ECU failure)
169 Cut--off relay in ECU does not switch off
170 No voltage supply at pin 30 or cut--off relay in ECU does not switch on
188 ECU fault -- wrong interrupt
189 ECU fault -- stack watch
192 ECU fault -- EEPROM access failure

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CODE FAILURE # FAULT

FF 11 Short circuit to ground at output stage to warning buzzer (E--Module)
56 Short circuit to ground at output SDP
58 Short circuit to positive at output SDP
114 Clutch engaged unintentionally in standstill, gear engaged
227 Application--Error database for CAN--communication

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 Date March 2003

SECTION 14
DRIVESHAFT

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 Date March 2003 Page 14-1

SECTION 14

DRIVESHAFT
CONTENTS OF THIS SECTION

SUBJECT PAGE
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-3
Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-3
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-3
Lubrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-3
Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-4
Driveshaft Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-4
U-Joint Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-4
Cleaning and Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-4
U-Joint Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-4
Driveshaft Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-4
Torque Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-5
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-5

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 14-2

1. YOKE -- DRIVESHAFT, FULL-ROUND

2. DUST CAP
3. GREASE FITTING -- SLIP-JOINT
4. UNIVERSAL JOINT
5. STRAP -- UNIVERSAL JOINT
6. TORX HEAD SCREW -- UNIVERSAL JOINT
7. LOCKSTRAP
8. CAPSCREW
9. YOKE -- TRANSMISSION, HALF-ROUND
10. YOKE -- DIFFERENTIAL, HALF-ROUND
11. FLINGER
12. DRIVESHAFT GUARD
9 13. DRIVESHAFT GUARD CROSSMEMBER
14. CAPSCREW

5
13
6

2
4 1

7 6

1 3
10
8
11
14

12
8 7

5464

FIGURE 1

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GENERAL DESCRIPTION
The driveshaft transmits power from the transmission
to the drive axle. The driveshaft is a two-piece unit with a
slip-joint and full-round end yokes. It uses two heavy
duty needle bearing universal joints. The differential and
transmission half-round yokes and the slip-joint simplify
driveshaft removal. (Figure 1)

COMPONENTS
Slip-Joint
The slip-joint is a heavy wall forging machined to
accept a splined shaft. A threaded dust cap and seal
prevent contamination. The slip-joint has a grease fitting
for lubrication. 5581

Universal Joint (U-Joint)

The U-joint has retaining cap bearings attaching it to FIGURE 2
the driveshaft yokes, and bearing cap straps attaching it
to the transmission and differential yokes. The driveshaft
uses 18 Series universal joints.

Slip-Joint Lubrication
CAUTION A grease fitting on the slip-joint is used to lubricate the
splined shaft. When installing a new driveshaft, grease
When assembling the driveshaft, the arrows the slip-joint after installation, before driving the coach.
at the slip-joint must be aligned. This aligns
To properly grease the slip joint:
the driveshaft end yokes.
1. Use the grease fitting to add grease until it appears
at the welch plug vent.
MAINTENANCE 2. Cover the welch plug vent with your finger. (Figure
3)
LUBRICATION
U-joints and the slip-joint should be greased every 3. Continue to add grease until it purges from the dust
10,000 miles (16,000 km) or 300 hours using lubrication seal.
specification S-17. Wipe all excess grease from the
driveshaft.

NOTE: Use NLGI No. 2, lithium 12-hydroxy stearate

grease. Lubrication intervals will vary with operating
conditions.

Universal Joint Lubrication

U-joints have grease fittings. To ensure proper
lubrication, add grease until new grease is forced out of
all seals (Figure 2). This fully lubricates the bearings and
removes contaminants.

NOTE: U-joint seals are designed to relieve. If a seal

does not “pop” when being lubricated, move the
driveshaft up and down and side to side while
applying grease gun pressure to the fitting. If
necessary, increase gun pressure. If seals still fail to
purge, remove the U-joint and correct the problem or FIGURE 3
replace the U-joint.

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INSPECTION U-JOINT REMOVAL

1. Remove the bearing cap capscrews at the
Inspect the driveshaft at regular intervals and every
full-round yokes.
lubrication interval.
2. Remove the caps.
1. Check U-joints for loose or broken bolts. (See 3. Remove the bearing cross from the yoke.
Torque Chart.)
CLEANING AND INSPECTION
2. Check for worn U-joints. Apply vertical loads of 50 1. Thoroughly clean grease from bearings, journals
lbs. (25 kg) to the U-joints. If movement exceeds and other parts.
0.006 inches (0.152 mm), replace the U-joint.
3. Check for a worn slip-joint. If radial play exceeds
0.007 inches (0.178 mm), replace the driveshaft.
CAUTION
4. Check for damaged tubing and dirt build-up. Bearing assemblies must be absolutely
5. Check for noise and vibration in the driveline. Noise clean. Even small particles of dirt can cause
and vibration may only be evident at certain rapid bearing wear.
speeds. Common causes of driveshaft and U-joint
vibration are: 2. Inspect yokes for cracks, wear or distortion.

a. Driveshaft out of balance. U-JOINT INSTALLATION

1. Installation is the reverse of U-Joint Removal. Note
b. Distorted or cracked yokes. the following:
c. Loose yoke strap capscrews. a. Ensure that all needles are in place.
b. A brass hammer may be used to lightly tap the
d. Yoke misalignment.
bearing caps into the yoke.
e. U-joint failure. c. Use new capscrews.
d. Hand tighten the capscrews, then alternately
tighten until properly torqued. See Torque
DRIVESHAFT REMOVAL Chart.
1. Switch the battery disconnect OFF. DRIVESHAFT INSTALLATION
2. Remove the driveshaft guard. 1. Collapse the driveshaft and install in reverse of
Driveshaft Removal. Note the following:
3. Remove the half-round straps at the differential a. If the slip-joint was separated, ensure that it is
yoke. properly aligned when assembled.
4. Remove the driveshaft from the differential yoke by b. Ensure correct orientation between the
collapsing the slip-joint. differential and transmission (Figure 1).
c. Use new capscrews.
5. Remove the half-round straps at the transmission
d. Hand tighten the half-round strap capscrews,
yoke.
then alternately tighten until properly torqued.
6. Remove the driveshaft from the coach. See Torque Chart.

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TORQUE CHART
Description Size lb-ft Nm
Full-Round Capscrews 3/8 --- 24 38 - 48 51 - 65
Half-Round Strap Capscrews 1/2 --- 20 115 - 135 155 - 183

SPECIFICATIONS
DRIVESHAFT
Part Number . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (See Parts Manual)
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Meritor
U-Joints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Series
Style . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Half-Round
Slip-Joint Spline Diameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3”
Slip-Joint Spline Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1/2”

MOTOR COACH INDUSTRIES

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 Date March 2003

SECTION 15
WHEELS, HUBS
AND TIRES
A -- Wheels
B -- Hubs
C -- Tires

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 Date March 2003 Page 15A-1

SECTION 15A

WHEELS
CONTENTS OF THIS SECTION

SUBJECT PAGE
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15A-2
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15A-2
Periodic Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15A-2
Wheel Removal and Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15A-3
Front and Tag Axles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15A-3
Drive Axle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15A-4
Torque Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15A-4

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GENERAL DESCRIPTION MAINTENANCE

Wheel Attachment
The wheels are hub-piloted and mounted with
two-piece flange nuts (Figure 1) that contact the wheel WARNING
face around the bolt hole. The wheels are located by the
hub-to-wheel interface. The wheel studs and nuts are
metric. The nuts are right and left-hand threaded on Never work under a unit supported only by a
jack. Always support the coach with stands.
opposite sides of the coach. The stud mount dual
Turn off the main battery disconnect switch.
wheels use an outer nut, which sandwiches both wheels Block the wheels before releasing the park
together against the hub. brake.
Wheels
NOTE: Wheels conform to The Tire and Rim
Association specification SAE J694. PERIODIC INSPECTION
1. Ensure that wheel stud nuts are properly torqued.
The wheel size on the J4500 is also different from See Torque Chart.
previous MCI coaches. Due to the 16,500 lb. front axle
rating, only 22.5 X 9.00 wide wheels are sufficiently rated NOTE: Tighten wheel stud nuts every 100 miles (160
to carry this load with 315/80R22.5 tires. km) for the first 500 miles (800 km), and whenever
NOTE: This tire mounted on a 8.25 wide wheel is also new wheels have been installed.
insufficiently rated to carry this load.
2. Inspect all wheels for cracks, bent bead rims or
Both steel and aluminum wheels are 22.5 x 9.00”. The other damage.
aluminum wheels are polished and have 10 hand holes.
The steel wheels are painted and have 5 hand holes.
NOTE: A worn hub face could be caused by running
with the wheels too loose. If the wear is not excessive,
CAUTION the entire hub face can be machined flat. Replace a
badly worn hub. Replace any broken or cracked
hubs.
Use only hub mount wheels and metric,
two-piece flange nuts.

HUB CAUTION
Painting wheels can affect the torque
retention of the wheel mounting nuts. Paint
thickness and hardness can affect the
torque retention of the nuts. 3.0 mil is the
maximum thickness allowed.
Wheel mounting nuts lose torque very
quickly on freshly-painted wheels. Allow
paint to cure before putting the wheels into
WHEEL
service. Baking will accelerate curing. Air
drying requires approximately seven days.

An excessively thick coat of paint can cause

a rapid loss of torque on the wheel nuts as
the paint wears away. Remove any excessive
TIRE paint from critical mounting surfaces.

FIGURE 1

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 Date March 2003 Page 15A-3

NOTE: Keep wheel studs and nuts free of grease and Front or Tag Axle Removal
oil. 1. Turn the front wheel straight ahead.
2. Run the flat tire up on the run-up block. (Figure 3)
When reusing two-piece wheel nuts, apply two drops Stop the coach and apply the parking brake. (The
of oil at one point between the nut flange and the thread run-up block is in the battery compartment. The
to allow the flange to rotate freely. Do not use excessive jack and lug wrench are in the spare tire
amounts of lubricant. Only USED nuts need lubrication. compartment.)

1/2”
NOTE: If extreme corrosion is a problem, apply a light 12.7 MM
application of anti-seize compound to the first three 10”
254.0 MM
threads of the studs or fluted inner wheel nuts.

24”
609.6 MM
12”

CAUTION
304.8 MM

4”
101.6 MM
7407
Anti-seize compounds may cause inaccurate FIGURE 3
fastening torques.
3. Place the bottle jack under the axle beam near the
wheel. Position the jack so that the ram of the jack
fits into the round recess at the bottom of the axle
WHEEL REMOVAL AND INSTALLATION beam. Operate the jack to partially raise the wheel
(Figure 4).

WARNING
Wheel and tire assemblies weigh more than
200 pounds (90 kg). Use caution while
unfastening the wheel from hub, and when
lifting it off the studs.

The spare tire is in a compartment directly behind the

front bumper (Figure 2). Release the bumper with the
lever in the front side service compartment.

FIGURE 4
4. Before the tire is completely off the ground, loosen
the wheel nuts.

WARNING
The wheel and tire assemblies weigh more
than 200 lbs. (90 Kg). Use caution when
loosening the wheel nuts, and when lifting
the wheel off the hub.

FIGURE 2 5. Raise coach completely, remove the run-up block,

and remove the wheel nuts.

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 Date March 2003 Page 15A-4

Front or Tag Axle Installation

Installation is the reverse of removal.
1. Before installing the wheels, lubricate the hub pilot
pads with an anti-seize compound to prevent
galling. Do not lubricate any other surface of the
wheel or hub.
2. Place one of the pilot pads at the 12 o’clock position
to center the wheel precisely and reduce run-out.
3. Ensure that the wheel is squarely mounted against
the hub before fully tightening the wheel nuts.
4. Torque the wheel nuts to between 400 - 500 ft-lbs FIGURE 6
(540 - 680 Nm) using the sequence shown in 3. Before the tire is completely off the ground, loosen
Figure 5. the wheel nuts.

WARNING
The wheel and tire assemblies weigh more
than 200 lbs. (90 Kg). Use caution when
loosening the wheel nuts, and when lifting
the wheel off the hub.

4. Raise the wheel completely, remove the run-up

block, and remove the wheel nuts and the wheel
and tire assemblies as required.
Drive Axle Installation
FIGURE 5 Installation is the reverse of removal.
1. Ensure that both wheels are properly seated to the
hub pilot before fully tightening the nuts.
Drive Axle Removal 2. Torque the wheel nuts to a value of between 400 -
500 ft-lbs (540 - 680 Nm), using the sequence
1. Run the inflated tire on the same side up onto the
shown in Figure 5.
run-up block. Stop the coach and apply the parking
brake.
2. Place the bottle jack under the drive axle beam and WARNING
near the wheel (Figure 6). Position the jack so that
the ram of the jack fits the recess at the bottom of The drive axle wheels are hub-piloted, so the
the jacking pad. The jack pad is on the rear face of outer wheels retain both the outer and inner
the drive axle beam below the suspension support wheels. Use caution when removing the nuts
structure attachment. Operate the jack and partially and tire assemblies.
raise the wheel.

TORQUE CHART

Front Axle Wheels (Hub-Piloted Aluminum or Steel) . . . . . . . . . . . . . . . . . . . . . . . . 400-500 ft-lbs (542-678 N.m)
Drive Axle Wheels (Hub-Piloted Aluminum or Steel) . . . . . . . . . . . . . . . . . . . . . . . . 400-500 ft-lbs (542-678 N.m)
Tag Axle Wheels (Hub-Piloted Aluminum or Steel) . . . . . . . . . . . . . . . . . . . . . . . . . 400-500 ft-lbs (542-678 N.m)

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Printed in Canada.
 Date March 2003 Page 15B-1

SECTION 15B

HUBS
CONTENTS OF THIS SECTION

SUBJECT PAGE
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15B-2
Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15B-2
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15B-2
Lubrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15B-2
Inspections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15B-3
Wheel Bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15B-5
Wheel Seals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15B-6
Service Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15B-7

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 Date March 2003 Page 15B-2

GENERAL DESCRIPTION MAINTENANCE

The coach wheels and drums are attached directly to
NOTE: Read each procedure completely before
the hub assembly. The hub is mounted to the axle
starting any maintenance.
spindle. All axle end wheel bearings are lubricated by oil
bath.
LUBRICATION
COMPONENTS Wheel bearing lube oil levels should be checked daily.
If low, add oil to the proper level. Use lubrication
Wheel End Assembly specification S-9 or S-10 (multi-purpose gear oil) or S-11
The forged hub is machined to accept oil seals, or S-12 (hypoid gear oil).
bearing cups, hub caps and wheel studs. Cup and cone
For oil change intervals refer to Section 10.
type tapered roller bearings are used on all axles. The
hub’s inner wheel seals, hub caps and axle flanges (rear Filling Front and Tag Axle Hubs
axle) seal the oil-lubricated hubs. Hubs have unitized
wheel seals.

Hub Cap CAUTION

Front and trailing axles have hub caps with integral
sight glass. The sight glass is used to check oil levels. A Do not overfill the hubs.
plug in the hub cap is used for adding oil (Figure 1).

1. Remove filler plug.

2. Fill hub with oil until it reaches the ring. Do not overfill
the hubs. (Figure 2)
3. Install the filler plug.

CAP SIGHT GLASS

LUBE PLUG

5480

FIGURE 1

Brake Drums
All axles have balanced brake drums.
OIL
NOTE: Machined brake drums may require MINIMUM REQUIRED OIL LEVEL IS INDICATED BY THIS
RING. DO NOT FILL MORE THAN HALF WAY BETWEEN
rebalancing to reduce vibration. Replacement drums THIS RING AND THE BOTTOM OF THE STOPPER PLUG.

must be balanced.
FIGURE 2
IMPORTANT: Wheel vibrations may be caused by:

A. Drums, wheels or tires out of balance. Filling Drive Axle Hubs

1. Remove the drive axle’s fill plug.
B. Improper attachment of wheels or hubs.
2. Fill until lube oil flows from the fill hole and plug.
C. Mismatched or worn tires.
3. Raise each axle end approximately 15 degrees to
D. Improperly inflated tires. allow lube oil to enter hub cavity.
E. Coach axles out of alignment. 4. Recheck oil level in axle and fill if necessary. Do not
F. Overloaded axle or suspension system. overfill the hubs.

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Printed in Canada.
 Date March 2003 Page 15B-3

17 24
15 21 22
23
7
8
20 19 9 11
6
18
16
3
2
1. OIL FILL PLUG 13. OUTER BEARING 12
2. CAPSCREW 14. OUTER BEARING CUP 13
3. LOCKWASHER 15. HUB
4. HUB CAP 16. INNER BEARING 10
5. GASKET CUP
6. SCREW --- BRAKE 17. INNER BEARING 14
DRUM MOUNTING 18. SEAL
7. DRUM 19. SPACER*
8. BEARING JAM NUT 20. OIL SLINGER 4
9. LOCKWASHER 21. NUT 1
10. LOCKRING 22. WASHER 5
11. DOWEL* 23. NUT
12. NUT 24. STUD Front and Tag Hub and Drum 5542

FIGURE 3

INSPECTIONS 8. Inspect the spindle and hub bore for nicks and
Every 100,000 miles (160,000 km) check the hubs for burrs, removing any that are found with an emery
correct bearing adjustment and end play. Also inspect cloth or file.
the wheel seals. Refer to Removal and Disassembly for 9. Inspect the bearings for excessive wear,
front, drive and tag axles. deterioration, cracking, scoring or pitting on the
bearing cups, rollers or cones. If present, the
Front and Tag Axles (Figure 3) bearings should be replaced following the ”Bearing
1. Block coach from moving, jack axle wheel end and Cup Replacement” procedure.
remove wheel. See Section 3 for lifting. See Wheel
10. When inspecting wheel seals, look for wear,
Removal.
distortion or damage at the sealing surfaces.
2. Unfasten hub retaining screws and remove brake Replace any damaged or defective seals. See Seal
drum. Replacement.
3. Bend up the tang on locking washer (9). Unfasten
and remove jamnut (8), locking washer and lock
ring (10). Remove bearing adjusting nut (12).
4. Unfasten hub cap mounting screws and CAUTION
lockwashers (2 & 3), and remove the hub cap (4)
and gasket (5). The tire, wheel, hub and drum assemblies
could weight over 300 pounds together. When
NOTE: Check for proper bearing adjustments at this making seal inspections, always remove the
time. If bearing are to be replaced or seal inspection is tire and wheel from the hub.
to be performed, continue with procedure.

5. Remove outer cone bearing (13), and pull the hub 11. Reassemble and mount components in reverse
assembly off the spindle. Use care to avoid damage order and perform a bearing adjustment.
to the seal assembly. 12. Reinstall hub cap using new gasket and
6. Remove inner cone bearing (17). lockwashers. Torque screws to 20-30 ft-lbs (27-41
7. Clean all the hub parts in a suitable cleaning N.m).
solvent, using a stiff brush to remove old lubricant 13. Check brake shoe pad adjustment and lubrication
and dirt. Using similar methods, clean any dirt or levels after completion of procedure. Install wheel.
other build-up from the spindle’s seal area. See Wheel Installation.

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 Date March 2003 Page 15B-4

Drive Axle Hub and Drum

5541

FIGURE 4

Drive Axle (Figure 4) and dirt. Using similar methods, clean any dirt or
1. Follow steps 1 & 2 of the pervious procedure. other build-up from the load tube seal areas.
7. Remove the wheel stud’s hex nut and washer
2. Remove axle shaft flange hex nuts (1), lockwashers
mounting oil slinger to rear of hub and remove.
(2) and dowels (3). Remove the axle shaft cover (4)
and gasket (5). 8. Unfasten and remove the seal retainer screws,
retainer (mounting seal & wiper), spacer (if present)
and gasket.
NOTE: Check for proper bearing adjustments at this
time. If bearing are to be replaced or seal inspection is 9. Inspect the load tube and hub bore for nicks and
to be performed, continue with procedure. burrs, removing any that are found with an emery
cloth or file.
10. Proceed with steps 9 through 11 of the previous
3. Bend up the tang on locking washer (if present). procedure.
Unfasten and remove jamnut (6) and lock ring (7).
11. Install the seal and retainer assembly onto the rear
Unfasten and remove bearing adjusting nut (8).
hub. Remount the slinger and torque hex nuts to
4. Remove outer cone bearing (9), and pull the hub 175-250 ft-lbs (237-339 N·m).
assembly off the load tube. Use care to avoid
12. Reinstall axle shaft cover using new gasket and
damage to the seal assembly.
lockwashers. Torque hex nuts or capscrews to
5. Remove inner cone bearing (20) and any seal 85-115 ft-lbs (115-156 N.m).
spacer (if present). 13. Check brake shoe pad adjustment and lubrication
6. Clean all the hub parts in a suitable cleaning levels after completion of procedure. Reinstall
solvent, using a stiff brush to remove old lubricant wheel using the torques given in section 15A.

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 Date March 2003 Page 15B-5

WHEEL BEARINGS

IMPORTANT: Wheel seal integrity can be

affected by excessive wheel bearing end play.
Incorrect wheel bearing adjustments will
eventually lead to bearing and/or seal failure.
When performing bearing adjustments, always
inspect the wheel seal for damage.

The following procedures are provided to properly

adjust the bearings and to determine wheel bearing
tolerances after adjustment.

WITH INDICATOR MOUNTED AT BOTTOM

Adjustment PUSH/PULL AT SIDES OF DRUM. 5623
1. Pry locking washer tab(s) up and off the outer hex
jamnut flats (when present). FIGURE 5
2. Remove the outer hex jamnut, lockwasher and Measuring End Play
lock-ring.
1. Attach a dial indicator with the magnetic base at the
3. Torque the outer bearing’s adjusting nut to 100 bottom of the brake drum (Figure 5).
ft.lbs. (136 N.m) while rotating the hub. This assures 2. Adjust the dial indicator so the pointer is against the
proper contact of all bearing surfaces. center of the spindle and the axis of each are
parallel. Set the dial indicator to zero.
4. Back the adjusting nut off 1 full turn and preload
bearing by torquing the adjusting nut while rotating 3. To measure the wheel end play, observe the dial
the hub as follows: indicator while pushing/pulling on each side of the
brake drum. End play is the total travel observed.
S Preload front & trailing axle bearings to 20 ft-lbs S End must be 0.001 - 0.005 inches (0.025 - 0.127
(27 N·m).
mm).
S Preload Drive axle bearings to 50 ft-lbs (68 N·m). 4. If the measurement is not within this range, repeat
the wheel bearing adjustment procedure.
5. Back off adjusting nut 1/3 turn.
6. Replace lock-ring with adjusting nut index pin Bearing Cup Replacement
inserted into one of the lock-ring holes and install 1. Where possible remove the old bearing cup (race)
lockwasher. by knocking it out from opposite end of hub. A long
steel drift or punch works well.
7. Install lockwasher (if used). 2. Clean and inspect the bearing cup bore. Remove
8. Install jamnut and torque: any nicks or burrs that may prevent new cup
installation with a file or emery cloth.
S Front and tag axles: 200 - 300 lb-ft (271 - 406 N·m).
3. Place the hub on a flat surface and properly locate
S Drive axle (without lockwasher): 250 - 300 lb-ft new cup over bore.
(240 - 406 N·m). 4. Using the old bearing cup, gently tap new cup into
S Drive axle (with bending tab lockwasher): 100 - its bore. This procedure sets the cup and prevents
150 lb-ft (136 - 203 N·m). cocking. A press can then be used to fully install the
bearing cup after it has been started.
9. Bend lockwasher tabs (if used) over the flats of the 5. Turn hub over and repeat procedure for remaining
jamnut. bearing cup.
10. Rotate hub to check final bearing adjustment and 6. Assemble wheel end components and adjust wheel
check end play. bearings.

MOTOR COACH INDUSTRIES

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 Date March 2003 Page 15B-6

WHEEL SEALS 3. Assemble the seal installation tool with the proper
bearing centering tool installed.
NOTE: Wheel seal designs can vary from one NOTE: Inner bearing cup and cone bearing must be
manufacturer to another. When replacing seals, in place to properly center seal installation tool.
always specify the OEM product. 4. Set smaller O.D. of seal in recess of tool adapter
(Figure 6).
IMPORTANT: MCI recommends that seals be 5. Properly locate the new seal over bore by inserting
properly installed by using only the seal bearing centering tool into inner bearing race. The
manufacturer’s prescribed installation tools. centering tool prevents cocking of the seal in the
The use of these tools assure correct bore (Figure 7).
placement of the seal. Improper installation
procedures or tools can cause seal damage or 6. Hold tool handle firmly and strike with hammer until
premature failures. seal is fully seated in bore.

NOTE: Seal installation tools may be purchased

through the seal manufacture.
Seal Replacement
1. With the hub positioned on a flat surface, carefully
pry old seal out of its bore or out of the retainer (drive
axle only).
2. Clean and inspect this bore for any nicks or burrs
that may prevent new seal installation. Remove
these with a file or emery cloth.
5537
FIGURE 7
NOTE: The sound of impact should change as seal
bottoms out.
7. After seal is installed, check for freedom of
movement by inserting fingers and moving interior
rubber component of seal backward and forward.

NOTE: A slight movement indicates damage free

installation.
5536
8. Assemble the wheel end components and adjust
FIGURE 6 wheel bearings.

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 Date March 2003 Page 15B-7

SERVICE TOOLS
SOME OF THE TOOLS USED FOR THE MAINTENANCE PROCEDURES
OUTLINED IN THIS SECTION ARE NONSTANDARD. THEY ARE AVAILABLE
FOR PURCHASE FROM MCI SERVICE PARTS OR, WHERE PRACTICAL, THEY
MAY BE FABRICATED BY THE SERVICE FACILITY.

7409 7412

20-56 Wrench - Front/Trailing Bearing Adjusting 20-168 Wrench - Rear Main Axle Bearing &
Nut Lock Nut

7411

20-167 Wrench - Front & Tag Axle Nut

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 Date March 2003 Page 15C-1

SECTION 15C

TIRES
CONTENTS OF THIS SECTION
SUBJECT PAGE
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15C-2
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15C-2
Inflation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15C-2
Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15C-2
Rotation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15C-2
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15C-4

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 Date March 2003 Page 15C-2

GENERAL DESCRIPTION J4500

FRONT . . . . . . . . 120 PSI (COLD)
J4500 coaches use special inter-city coach tires DRIVE . . . . . . . . . 100 PSI (COLD)
TAG . . . . . . . . . . 120 PSI (COLD)
designed for on-highway service. These tires are
steel-belted radials, and carry a J load rating. The tire
size is 315/80R22.5, and the tires mount on 22.5 x 9.00 REPLACEMENT
wide rims. Due to the 16,500 lb. front axle rating, only this Always replace tires with the same size and rating tire
size tire mounted on a 9.00 wide rim carries a sufficient as originally came with coach or poor engine and
load rating for this application. This size tire mounted on transmission performance will result.
a narrower rim is not sufficiently rated. Use only ROTATION
315/80R22.5 tires mounted on 9.00 wide rims. NOTE: Before rotating tires, consult the tire
The only exception to this requirement is for snow manufacturer. They are the source for directions
tires on the drive axle. In a dual tire application, 12R22.5 relating to specific tires.
or 12.75R22.5 tires on a 9.00 wide rim also carry a Rotate radial tires only when necessary. If irregular
sufficient rating. This is true only for the drive axle; the wear becomes apparent, or if the wear rate on the tires is
front axle must use 315/80R22.5 tires on a 9.00 wide rim. uneven, rotate the tires. There is no restriction on
crisscross rotation.
MAINTENANCE Install new tires on the front wheels where they run
coolest.
Inspect tires daily: carefully inspect for cuts or foreign Safety Precautions
matter such as nails, glass, etc. Remove any foreign
matter lodged in tire treads or between dual wheels.
WARNING
INFLATION Exercise care when handling wheels and
Check tire inflation pressure with an accurate gauge. tires. Only trained and qualified employees
Check the pressure before starting a run and as may service wheels and tires. Respect the
explosive force contained in an inflated tire.
recommended by the tire manufacturer. Always use the
same gauge to check the pressure, to eliminate any Follow safe shop practice. Wear safety
differences resulting from gauge error (Figure 1). glasses when performing service or
maintenance procedures.
If the pressure loss is greater than normal, remove
and inspect the tire to determine the cause. Replace any Do not hit steel wheels with steel hammers.
missing valve caps. Metal shards may break off the wheels and
cause injury.

NOTE: Check tire pressure with pressure cold. 1. When servicing tires, do not to drop them on the
feet, hands or body, or heavily on the floor. When
The valve core is a spring-loaded check valve in the carrying tires or wheels, avoid oil and objects on the
stem that permits tire inflation. The valve seals the air in floor. Keep the floor clean and dry (Figure 1).
the tire. When the valve cap is tightened on the stem, the
2. Deflating a tire by first reducing pressure as much
sealing washer inside the cap presses tightly against the
as possible by pushing the valve core plunger.
top of the stem, preventing air leaks.
Keep your eyes away from the valve. Remove the
All tires on the same axle should always carry the valve core to ensure complete deflation.
same air pressure. A 5 psi (34.5 kPa) underinflation in 3. Dismount tires on drop center rims handled on a
one front tire can not only cause hard steering, but can wheel holder, or tire changing machine to prevent
create steering hazards which may cause an unsafe cuts on the hands and wrists. Use only standard tire
condition. An underinflated rear tire can seriously affect mounting tools and equipment.
braking. 4. After removal, inspect the tire carefully and do all
Recommended inflation pressures for max. necessary repairs. A tire spreader is helpful, but use
interstate/interprovincial allowable axle loads are shown care when working around it. Keep spreader arms
below and in the tables at the end of this section. closed when the machine is idle.

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 15C-3

5. Inspect wheel parts carefully for rust, damage, or 6. Stand away from the valve stem as far as possible
distortion. Never use wheels which are out of when inflating tires. Avoid a position where the face
shape, rusted, cracked or broken in any way. Never or body is immediately over the work being done on
use a ring or other rim parts other than from the any tire in which there is pressure. Use only
rim’s manufacturer or of a type other than supplied accurate, tested gauges to ensure proper air
with the coach. pressure.

CHANGING TIRE ON DROP

HANDLING WHEELS AND TIRES SAFE AIR REMOVAL CENTER RIM

USE OF TIRE IRONS TIRE SPREADER CAREFUL VISUAL INSPECTION

SEATING OF RINGS INFLATION PRECAUTIONS 7413

FIGURE 1

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 Date March 2003 Page 15C-4

Tire Inflation Chart

Make and type Size Front Axle Drive Axle Tag Axle
Goodyear G391 315/80R22.5 120 psi (827 kPa) 100 psi (690 kPa) 120 psi (827 kPa)
Goodyear G124 (Snow tires) 12R22.5 Not approved 100 psi (690 kPa) Not approved
Michelin XM + S4 (Snow tires) 12R22.5 Not approved 100 psi (690 kPa) Not approved
Firestone HP3000 315/80R22.5 120 psi (827 kPa) 100 psi (690 kPa) 120 psi (827 kPa)
Goodyear G291 315/80R22.5 120 psi (827 kPa) 100 psi (690 kPa) 120 psi (827 kPa)
Michelin PXZA 1 315/80R22.5 120 psi (827 kPa) 100 psi (690 kPa) 120 psi (827 kPa)

GROSS VEHICLE WEIGHT RATINGS

GVWR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54,000 lbs. (24,490 kg.)
Front Axle GAWR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16,500 lbs. (7,480 kg.)
Drive Axle GAWR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23,000 lbs. (10,430 kg.)
Tag Axle GAWR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16,500 lbs. (7,480 kg.)

SPECIFICATIONS
MANUFACTURER GOODYEAR GOODYEAR GOODYEAR FIRESTONE

TREAD PATTERN G391 G124 G291 HP 3000

SIZE 315/80R22.5 315/80R22.5

315/80R22.5 12R22.5

LOAD RANGE “J” “H” “J” “J”

18
PLY RATING 18 16 18

STATIC LOAD RAD. 19.9 20.2 19.7 19.7

MPH (KM/M) 75 (120) 65 (105) 75 (120) 75 (120)

MAX. SPEED

MAX. RATING 8820 LBS N/A 8270 LBS 8270 LBS

@125 PSI @120 PSI @ 120 PSI

(SINGLE) N/A

MAX. RATING 7390 LBS 6750 LBS 7610 LBS 7160 LBS

(DUAL) @125 PSI @120 PSI @120 PSI @ 120 PSI

REV’S / MILE 490 482 491 491

OUTER DIA. 42.4 43.1 42.3 42.3

WIDTH FREE 12.5 11.2 12.4 12.1

WIDTH LOADED 13.6 12.4 13.5 13.2

WEIGHT LBS 145 147 145 146

HUBOMETER DOM. 7L-8-1092 7F-8-223 7L-8-1092 7L-8--- 1092

HUBOMETER METRIC 7L-8-1135 7L-8-1095 7L-8-1096 7L-8-1096

MOTOR COACH INDUSTRIES

Printed in Canada.
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 Date March 2003

SECTION 16
HEATING AND
AIR CONDITIONING

A - Heating and Air Conditioning System

B - Auxiliary Heater

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SECTION 16A

HEATING AND AIR CONDITIONING SYSTEM

CONTENTS OF THIS SECTION

SUBJECT PAGE
Important Notice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16A-2
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16A-2
Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16A-4
Air Conditioning Refrigerant Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16A-11
Heating (Engine Coolant) Flow Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16A-11
Main Controller Data Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16A-13
Main Control Box . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16A-15
Safety Devices for Main Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16A-17
Driver’s HVAC Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16A-18
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16A-20
Pre-Trip Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16A-20
Starting, Stopping and Operating Instructions . . . . . . . . . . . . . . . . . . . . . 16A-20
Operational Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16A-20
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16A-23
Maintenance Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16A-24
Air Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16A-25
Manifold Gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16A-25
Checking for Non-Condensable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16A-26
System Pump Down and Charging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16A-26
System Checks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16A-28
Condenser . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16A-32
Main Evaporator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16A-34
Parcel Rack Evaporator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16A-35
Driver’s Control Box . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16A-36
Driver’s Evaporator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16A-36
Passenger’s RAM Air Actuator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16A-37
Duct Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16A-37
Compressor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16A-38
Electronic Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16A-42

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 Date March 2003 Page 16A-2

CONTENTS OF THIS SECTION (continued)

Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16A-45
Microprocessor Error Message Definition . . . . . . . . . . . . . . . . . . . . . . . . . 16A-45
Diagnostics from the Driver’s Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16A-45
Driver Display Panel Alarm Message Definitions . . . . . . . . . . . . . . . . . . . . 16A-46
General System Troubleshooting Procedures . . . . . . . . . . . . . . . . . . . . . . 16A-49
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16A-52
Service Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16A-55

IMPORTANT NOTICE service instructions on the HVAC system itself, please

refer to the Operator’s Manual and the Carrier Manual
The HVAC (heating, ventilating, and air conditioning) provided with this coach.
system is supplied by Carrier Transicold. Servicing,
The equipment components consist of a condenser,
especially during the warranty period, should be
main evaporator and heater, driver evaporator and
referred to an authorized Carrier Transicold service
heater, optional parcel rack evaporators, compressor,
center. For this information, call MCI at 1-800-241-2947.
main controller, driver fan controller, driver display and
check valve assemblies, humidity and temperature
GENERAL DESCRIPTION sensors and a coolant bypass control valve.
This section contains maintenance instructions The air conditioning and heating equipment
pertaining to the interface between the Heating, interfaces with electrical cabling, refrigerant piping,
Ventilating and Air Conditioning (HVAC) system installed engine coolant piping for heating, ductwork and other
in the J series coach (Figure 1). For operating and components furnished by MCI to complete the system.

TABLE 1. Part (Model) Number Chart

Model No. Refrigerant Controller Fan Motors Parcel Rack Connection

68G4-101 R-134a Microprocessor Wound Field No

68G5-101-4 R-134a Microprocessor Wound Field No
68G5-101-7 R-134a Microprocessor Wound Field Yes
68G5-101-10 R-134a Microprocessor Wound Field No
68G5-101-11 R-134a Microprocessor Wound Field Yes

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DRIVER DISPLAY
DRIVER’S
EVAPORATOR
ASSEMBLY AND DRIVERS RAM AIR
DAMPER

FRONT OF COACH
PASSENGER RAM AIR DAMPER

PARCEL RACK EVAPORATORS

(OPTIONAL)

MAIN
CONTROLLER

CURBSIDE
RETURN AIR
TEMPERATURE/
HUMIDITY SENSOR

CHECK
DRIVER BALL VALVE
VALVE DRIVER
CONTROL
BOX

EVAPORATOR
ASSEMBLY

ROADSIDE
CONDENSER RETURN AIR
ASSEMBLY TEMPERATURE
SENSOR
COMPRESSOR
ENGINE ASSEMBLY
BALL
VALVES COOLANT
BOOSTER
AUXILIARY PUMP
HEATER
(OPTIONAL)

COACH CUTAWAY VIEW

FIGURE 1

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COMPONENTS Fuses
Power to the heating and air conditioning is controlled Two fuses in the main fuse box supply outputs for the
through several means: circuit breakers, fuses, and main HVAC controller (Figure 3). Table 2 describes the
relay module outputs. fuse ratings, types, and functions.
Breakers
Five circuit breakers and internal thermal protection
switches protect evaporator and condenser fan motors
against overcurrent and overheat.(Figure 2). Table 3
contains details of the circuit breaker’s size, type, and
function.

HVAC FUSES

FIGURE 3: HVAC Fuses

FIGURE 2: Circuit Breakers

TABLE 2. FUSES
Fuse No. Amps Type Function Location
18 15 Fuse Power to 24V outputs from main HVAC Fuse box (a) battery bay
controller
20 15 Fuse Power to 24V outputs on expansion board Fuse box (a) battery bay
or relay pack in main controller box
3 coolant control valves
2 linear actuators on ram air dampers
Clutch relay

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TABLE 3. CIRCUIT BREAKERS

Breaker No. Amps Type Function Location
1 70 Auto Reset Main evaporator: curb side Battery Bay
2 70 Auto Reset Main evaporator: road side Battery Bay
3 50 Auto Reset Front condenser fan motor Battery Bay
4 50 Auto Reset Rear condenser fan motor Battery Bay
5 40 Auto Reset Driver’s evap control box Battery Bay
15 Auto Reset Driver evaporator motor Driver’s Control Box
15 Auto Reset Driver evaporator motor Driver’s Control Box
17 15 Auto Reset Parcel rack blowers: curb side Fuse Box in Battery Bay
19 15 Auto Reset Parcel rack blowers: road side Fuse Box in Battery Bay

Driver’s Display service valves, high pressure switch, pressure

Power to the 12 volt display is supplied from module 9, transducers, suction and discharge servicing (charging)
output 6. It is protected by a PolyfuseTM. Modules are ports and electric solenoid unloaders.
located in the module box on the ceiling in the first For more detailed information on the compressor,
curbside baggage bay. refer to Carrier Transicold manual number 62-02756.
Microprocessor
Power to the 12 volt microprocessor is supplied from
Evaporator Assemblies
module 3, output 14. It is protected by a PolyfuseTM.
Power is supplied to the microprocessor through the The evaporator assemblies include a driver zone
same logic as the starter cirucit: i.e., the engine must be evaporator assembly, a passenger zone evaporator
running before the microprocessor will be powered to assembly and curbside and roadside parcel rack
operate all HVAC functions. evaporators.

Condenser Assembly Each evaporator assembly includes:

The condenser assembly includes a condenser coil, S fan and motor assembly,
fan and motor assemblies, filter-drier, control box, main S evaporator coil assembly,
and parcel rack liquid line solenoid valves, king valves S heater coil assembly (except parcel rack
and an ambient temperature sensor (Figure 4). assemblies),
The liquid line is fitted with a sight glass to check liquid S thermal expansion valve,
refrigerant level. The condenser is also fitted with a S condensate drain connection(s),
fusible plug which protects the system from unsafe high S evaporator heat valve (except parcel rack
operation conditions. assemblies),
The control box includes condenser fan relays which S air filter.
control the speed of both condenser fans. The driver evaporator has an actuator which controls
The main liquid line solenoid valve closes when the the outside (RAM) air damper.
system is shut down. The evaporator heat valve controls the flow of engine
coolant water supplied to the heating coils.
Compressor Assembly
The compressor assembly includes the refrigerant The condensate drain disposes of condensate
compressor, clutch assembly, suction and discharge collected on the evaporator coils during cooling.

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25 12
13
9 11, 18, 19, 26, 27 13

12, 25

10

End View (within compartment) Front View (from road side)

2 3
9
13 1. Filter Drier
2. Liquid Line Service Valve
12, 25 3. King Valve – Discharge Line Service Valve
4. 1/2″ ORS Fitting assembly
5. 1/2″ O.D. O-Ring
6. Solenoid Coil
7. Repair Kit
1 8. 24 VDC Contactor
9. Condenser Coil Assembly
10. Control Box cover
11. 8 HP Condenser Motor
12. Fan Guard
13. Venturi Ring
14. Liquid Sight Glass
15. Solenoid Valve Repair Kit
14 16. Fusable Plug
17. 24 VDC Solenoid Valve Coil
18. Motor Brushes Holder
3 19. Opposite End Bearing
20. King Valve Cap (Service Part)
21. 1-7/8″ ORS O-Ring
10
22. Receptacle
End View (within compartment) 23. 3/8-16x2.0 Steel Stud
24. 3/8-16x2.07 Brass Stud
25. Fan Propeller (Blade)
NOTE: The location of all components is not
26. G.E. End Shaft Bearing
shown. The Illustrations are for general refer-
27. Brushes
ence only. Items in bold are indicated on the 28. Thermistor Ambient Sensor
illustrations. 29. Schraeder Valve (Braze)
30. 3/8-16UNC X 2.25 Negative Battery Stud
31. 3/4″ O-Ring

FIGURE 4. Condenser Assembly

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12
5

10

11 8 13

Rear View 14
3
7

2
9

1. Thermo Expansion Valve

2. Solenoid Valve
3. HVAC Access Panel Foam
4. Driver’s HVAC Front Foam
5. LH Supply ducts RH Gasket Front View
6. Driver’s HVAC Assembly
7. Solenoid Valve Coil
8. Air Filter
9. Driver’s HVAC Side Foam
10. Heater Coil sub---Assembly
11. A/C Coil Sub---Assembly
12. Blower Motor assembly
13. Linear Operator
14. 1 in. O-Ring

FIGURE 5. Driver Evaporator Assembly

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3, 12 2, 13 19
6 9, 21 9, 21 6

5, 8

5, 8

14, 15, 16 4, 18 16
15

14
1, 17, 20
7, 10, 11 4, 18

End View Rear View (showing Blower Motor & Fans)

1. Contactor 3, 12 2, 13
19
2. 2.0 in. O.D. Discharge O-Ring
3. 2.0 in. O.D. O-Ring
4. Shock Mount
5. 1/4---18NPT Valve
6. Evaporator / Heater Coil Assembly 5, 8
7. Low Side Charge Port Valve Body
8. Tee Handle Valve 6
9. Expansion Valve --- w/o Flange
10. Core Valve
11. Cap
12. Suction Line fitting Assembly
13. Suction Line fitting Assembly
14. Evaporator Blower Motor
15. L/H Blower Fan Housing Assembly
16. R/H Blower Fan Housing Assembly
17. Relay Mounting Base
18. Motor Mount
5, 8
19. Coolant Valve
20. 24 VDC Relay (single pole/double throw) NOTE: Blower motor and L/H, R/H blower fans
21. Thermal Expansion Body Valve Flange not shown in photograph of Evaporator / Heater
Coil assembly for clarity.

FIGURE 6. Evaporator Assembly

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5 6 7 8 9
4

3
10
2
1

1. Suction Outlet Connection 6. Evaporator Coil Assembly

2. Liquid Inlet Connection 7. Parcel Evaporator Fan and Motor
3. Side Access Panel 8. Motor Mount
4. Top Access Panel 9. Relay
5. Thermal Expansion Valve 10 Condensate Drain Connection

FIGURE 7. Parcel Rack Evaporator

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Printed in Canada.
 Date March 2003 Page 16A-10

DRIVER
EVAPORATOR
DRIVER’S ASSEMBLY
SOLENOID
VALVE THERMAL
EXPANSION
VALVE

EVAPORATOR COIL

CURBSIDE
EVAPORATOR
ASSEMBLY

EVAPORATOR COIL

LIQUID LINE

MAIN LIQUID LINE

SOLENOID VALVE

PARCEL RACK
SOLENOID
VALVE
PARCEL RACK EVAPORATOR ASSEMBLY
(Optional)

SERVICE

SIGHT GLASS VALVE

PARCEL RACK EVAPORATOR ASSEMBLY

(Optional)
SUB
COOLER
CONDENSER
ASSEMBLY

SERVICE VALVE
SUCTION LINE

DISCHARGE LINE COMPRESSOR

CHECK VALVE

FIGURE 8. Air Conditioning Refrigerant Flow Diagram

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Printed in Canada.
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AIR CONDITIONING REFRIGERANT through the driver solenoid valve and to the driver
CYCLE thermal expansion valve. The solenoid valves open
When air conditioning (cooling) is selected by the during cooling to allow refrigerant to flow to the thermal
main controller, the unit operates as a vapor expansion valves. The main liquid solenoid valve and the
compression system using R-134a as a refrigerant. The parcel rack liquid line solenoid valve (when so equipped)
main components of the system are the reciprocating closes during shutdown to isolate the refrigerant in the
compressor, air-cooled condenser coil, subcooler, condenser. The thermal expansion valves reduce the
filter-dryer, thermostatic expansion valves, liquid line pressure and temperature of the liquid and meters the
solenoid valves and evaporator coils. flow of liquid refrigerant to the evaporator to obtain
The compressor raises the pressure and the maximum use of the evaporator heat transfer surface.
temperature of the refrigerant and forces it through the When ventilation only is selected by the main
discharge line, through the check valve into the controller, only the evaporator fans function to circulate
condenser tubes. The condenser fan circulates air throughout the coach. The refrigerant cycle will
surrounding air over the condenser tubes. Heat transfer remain off.
is established from the refrigerant to the condenser air.
This removal of heat causes the refrigerant to liquefy and HEATING (ENGINE COOLANT) FLOW
flow to the receiver. CYCLE
The main liquid line is equipped with a sight glass to Heating circuit components include heater cores and
observe the refrigerant for the correct system charge evaporator heat valves for each evaporator assembly,
level. auxiliary heater (optional), coolant boost pump, hand
The refrigerant leaves the condenser and then flows valves and “Y” type strainers.
through the subcooler, liquid line service valve and The main controller cycles the valves during heating
filter-dryer where an absorbent keeps the refrigerant and reheat cycles to maintain the required temperatures
clean and free of water. inside the coach.
From the filter-dryer, the liquid refrigerant then flows When the evaporator heat valve is de-energized, the
through the main liquid solenoid valve and parcel rack valve will open to allow engine coolant to flow through
evaporator solenoid valve (if this option is active) to the the heater coil (Figure 9). The valve is normally open so
passenger evaporator thermal expansion valve and that if a failure occurs, heat will flow into the coach.

MOTOR COACH INDUSTRIES

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CONTROL VALVE

HAND VALVE
DRIVER HEATER CORE

“Y” STRAINER CONTROL VALVE

CONTROL VALVE

“Y” STRAINER

MAIN HEATER CORE HAND VALVE

HAND VALVE

AUXILIARY
HEATER (OP-
TIONAL)

AUXILIARY
HEATER
PUMP

ENGINE
COOLANT ENGINE WATER
BOOST PUMP
PUMP

FIGURE 9. Heating System Flow Diagram

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Printed in Canada.
 Date March 2003 Page 16A-13

MAIN CONTROLLER DATA FLOW (microprocessor module), receptacle, quick

The system is supplied with 12/24 vdc power from the connectors, connectors and fuses (F2) and (F3). (See
coach power supply. The main controller receives input Figure 12.) The main controller (microprocessor
from pressure transducers, temperature sensors, a module) measures inputs and processes the outputs to
humidity sensor, condenser and evaporator fan motor automatically control the air conditioning and heating
overloads, high pressure switch and fuses. system to maintain temperatures and humidity inside
It then processes these inputs to control output the coach. The microprocessor section has a self-test
devices, enabling automatic control of temperature and feature executed at system power---up. The relays or
humidity conditions inside the coach. The driver display expansion board drive discrete outputs besides the
communicates with the main controller. standard outputs from the controller.
The following block diagram (Figure 10) describes
data flow through the system. Refer to “Operation” in the Driver Control Box
following pages for more detailed information on the
control system’s theory of operation. The driver control box is located under the right
headlamp and includes a battery positive stud, battery
Main Control Box negative stud, connector, relay and two driver’s blower
The main control box includes a main controller motor circuit breakers.

24 VDC
MCI HVAC
POWER
PARAMETER
SUPPLY
READER
12 /24 VDC
POWER
SUPPLY

RS--232

Fan Motors,
Contactors Coolant Boost
Pump

INPUT
DEVICES
(Transducers,
Sensors and MAIN CONTROLLER
HP switch)

12 VDC
POWER
SUPPLY

OUTPUT DEVICES
RELAY BOARD (Heat Solenoid Valves, Ram
DRIVER HVAC OR Air)
CONTROLLER EXP. BOARD
COMPRESSOR CLUTCH

MAIN CONTROL BOX

24 VDC
POWER
SUPPLY

FIGURE 10. Electronic Data Flow Block Diagram

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 Date March 2003 Page 16A-14

1 2 3

6 5 4

1. Battery Power Negative Stud 4. Driver Control Circuit Breaker No. 2 (DCCB2)
2. Battery Power Positive Stud 5. Driver Control Circuit Breaker No. 1 (DCCB1)
3. Connector 6. Driver control Fan Relay

Figure 11. Driver Control Box

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 Date March 2003 Page 16A-15

MAIN CONTROL BOX coach. The microprocessor section has a built-in

The main control box, located in the battery memory facility for checking proper operation; this
compartment, includes a main controller includes checks of the program memory, data memory
(microprocessor module), four relays or an expansion and analog and discrete inputs and outputs. It has a
output board with separate relay for clutch and self-test feature which is executed when the system is
condenser, receptacles quick connectors, connectors powered up. The expansion board or relay board drives
and fuses (F2) and (F3). (See Figure .) The main discrete outputs besides the standard outputs from the
controller (microprocessor module) contains the controller. The four relay board drives four discrete
electronic hardware to measure inputs and process the outputs besides the standard outputs from the
outputs to automatically control the air conditioning and controller.
heating system to maintain temperatures inside the

1 2 3 4 5 6 7 8 9 10 14

24V
11
12V

12V

12V

14 13 12
A THRU K L THRU Y

1
2
3

1 Connector (MA) 10 Connector (KB)

2 Connector (MB) 11 Relays
3 (Not Used) 12 Main Controller
4 Fuse (F2) 13 Connector (EC) Pins L-Y
5 (Not Used) 14 Connector (EC) Pins A thru K
6 Fuse (F3)
7 (Not Used)
8 Quick Connector (QC1)
9 Connector (KA)

FIGURE 12. Main Control Box with Relay Board

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 Date March 2003 Page 16A-16

1 2 3 4 5 6 7 8 9 10 11 12 13 14

15

19

18 17 16
A THRU K L THRU Y

1
2
3

1 Connector (MA) 10 Connector (KB)

2 Connector (MB) 11 Connector (MA)
3 (Not Used) 12 Quick Connector (QC2)
4 Fuse (F2) 13 Connector (MB)
5 (Not Used) 14 Canon Connector
6 Fuse (F3) 15 Expansion Board
7 (Not Used) 16 Main Controller
8 Quick Connector (QC1) 17 Connector Pins A thru K
9 Connector (KA) 18 Connector Pins L thru Y
19 Relay-Clutch and Condenser

Figure 13. Main Control Box with Expansion Board

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SAFETY DEVICES FOR MAIN CONTROLLER

Safety Devices circuit from excessive current draw.
System components are protected by safety devices. During the A/C mode, HVAC system operation will
These include a high pressure switch, thermal switches, automatically stop if the HPS switch contacts open due
fuses and circuit breakers. to an unsafe operating condition. Opening the HPS
Internal to the controller, the fuse (F2) protects the contacts de-energizes, through the main controller, the
controller 12 vdc supply circuit from excessive current A/C compressor clutch and condenser fan motor relays,
draw. Fuse (F3) protects the controller 24 vdc output shutting down the system.

TABLE 11. Safety Devices

Unsafe Condition Safety Device Device Setting Location
1.High compressor discharge pressure 4. High Pressure Opens at: 385 ±10 psig Compressor
Switch (HPS) (2.6 mPa ±6.9 kPa )
Closes at: 285 ±10 psig
(2.0 mPa ±6.9 kPa)
2.Excessive current draw by the controller 5.Fuse (F2) Opens at 5 amps Main Controller
12 vdc supply circuit
3.Excessive current draw by the controller 6. Fuse (F3) Opens at 15 amps Main Controller
24 vdc output circuit

Condenser Motor Overloads Evaporator Motor Overloads

The roadside and curbside evaporator fan motors are
Each condenser fan motor is equipped with an internal equipped with internal thermal protector switches. If
thermal protector switch. If excessive motor temperature excessive motor temperature exists, the switch will open
exists, the switch will open to de-energize the to de-energize the corresponding evaporator fan relay to
corresponding condenser fan relay to stop the affected prevent the affected evaporator motor from operating on
condenser motor. high speed

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DRIVER’S HVAC CONTROL/DISPLAY

DEF HEAT
auto cool

00.0 °F vent heat

1/0 temp recirc/ fan speed

fresh air

DRIVER’S DRIVER’S
FAN HEAT
CONTROL CONTROL COACH HVAC DISPLAY

I/O ON/OFF Toggles system from ON to OFF. When the ON/OFF key is toggled, the HVAC system
turns off. When the system is first powered up, it will
momentarily show current software level and do a self-
test with all VFD segments and keypad LEDs turned on.
After self-test, the display will show temperature set
point. When off, the display will be blank.
Y UP (INCREASE) Increases passenger temperature
SELECTION set point.
B DOWN (DECREASE) Decreases passenger tempera-
SELECTION ture set point.
temp TEMPERATURE Select to show set point or pas- The display shows passenger temperature set point.
DISPLAY SELECTION senger return air or ambient tem- Press the key to toggle to the passenger return air tem-
perature. perature, ambient temperature, then return to set point.
The appropriate LED will be turned on.
recirc/ RAM AIR SELECTION Selects closed ram air, open ram At power up, the ram air is auto-controlled by the pas-
fresh air air or automatically controls fresh senger return air temperature and ambient tempera-
air. ture. Press the recirc key to toggle the ram air to closed,
open, then return to AUTO. The appropriate LED will be
turned on.
fan speed FAN SPEED Selects low or high fan speed on When the system is first powered up, the evaporator fan
SELECTION main evaporator or automatically speed is auto-controlled by the cooling/heating require-
control fan speed. ment. Press the fan speed selection key, to toggle the
fan from low speed to high speed, then return to AUTO.
The appropriate LED will be turned on.
auto AUTO SELECTION Automatically decides operation When the system is first powered up, it will run in auto
mode based on cooling or heating mode, which determines whether cooling, heating or
capacity requirement. re-heat is required. The LED will be turned on when in
auto-control.
cool COOL SELECTION Runs in cooling mode only. If Press the cool mode selection key to put the system in
cooling is not required, then sys- cool only mode. If the controller calls for heating, the
tem will run ventilation. system will go to ventilation mode. The LED will be
turned on.
heat HEAT SELECTION Runs in heating mode only. If Press the heat mode selection key to put the system in
heating is not required, the sys- heat only mode. If the controller calls for cooling, the
tem will run ventilation. system will go into ventilation mode. The LED will be
turned on.
vent VENT MODE Runs evaporator fan in low speed Press the vent mode selection key to turn off the A/C
SELECTION only. and heating system. Evaporator fan will run in low
speed. The LED will be turned on.

MOTOR COACH INDUSTRIES

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 Date March 2003 Page 16A-19

_F and _C Selection preheating, the temperature-dependant control

Press and hold the temperature selection key and overrides the timer.
press UP key to select _F. Press and hold the
temperature selection key and press DOWN key to
select _C.

Alarms
When a suction or discharge pressure alarm is
present, the display will toggle between the alarm (e.g.
A23 or A27) and temperature setpoint. When both DRIVER’S A/C
passenger temperature sensors are faulty, ---40 will
AUXILIARY HEATER
show on the screen.

Driver’s Fan (Defrost) Control

Controls driver’s defroster fan speed from 30% to
maximum. Push fully up for maximum defrost.

Driver’s Heat Control FIGURE 14 -- Left Side Console

Controls driver’s heat from 0 to 100%. Push fully up for
maximum heat and defrost.
Parcel Rack Ventilation Switch
Driver’s A/C Switch Located on the right-hand switch panel, the PARCEL
RACK switch turns the parcel rack blowers on and off. If
The DRIVER’S A/C switch is located on the left side the coach is equipped with parcel rack A/C, this switch
console. (Figure NO TAG) When the switch is on AUTO, turns the parcel rack A/C on and off. See Figure NO TAG.
the driver’s area heating and cooling is controlled by the
controller. When the switch is on COOL , the driver’s area PARCEL RACK SWITCH
is demanding cooling, even if the passenger area is in
heating.

Auxiliary Heater Switch

The AUXILIARY HEATER switch is located on the left side
console. (Figure NO TAG) When the engine is off, the
engine can be preheated by pushing the AUXILIARY
HEATER switch forward, which activates a 90 minute timer
in the Proheat unit. When the Proheat burner is on, the
HEATER ON telltale lights.
To turn the Proheat off, push the switch back. It will
purge for 2 to 3 minutes. If the coach is started during FIGURE 15 -- Right-Hand Switch Panel

MOTOR COACH INDUSTRIES

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 Date March 2003 Page 16A-20

OPERATION During reheat, the main and driver’s compartment

liquid solenoid valve are opened and the main heat valve
cycled to maintain temperature in the passenger
PRE-TRIP INSPECTION
compartment.
After starting system operation, allow the system to
stabilize for ten to fifteen minutes and check for the Main Compartment Evaporator Fan Speed
following: Selection
1. Listen for abnormal noises in the compressor or fan The main compartment air conditioning unit is
motors. equipped with a two-speed fan motor. Temperature
2. Check the compressor oil level. (Refer to the control is the primary method of determining the fan
maintenance subsection). speed selection. The exceptions are:
3. Check the refrigerant level. (Refer to the 1. The high speed for pull up or pull down on the main
maintenance subsection). evaporator fan is limited to a maximum of 30
minutes and can only be put in high speed once by
4. Ensure that self-test has been successfully
the controller. The driver’s display cannot override
performed and that there are no errors or alarms
the fan speed to extra high.
indicated.
2. The minimum runtime in high or low for the main
STARTING, STOPPING AND OPERATING evaporator fan is three minutes in automatic
INSTRUCTIONS control.

NOTE: The coach engine must be operating at idle Driver Compartment Control
speed or faster for the HVAC system to start. The driver compartment temperature is controlled by
setting the HEAT slide control to the left of the HVAC
At engine start up, the HVAC system starts driver’s display to the desired position. The controller
automatically. The driver’s HVAC display does a self test then cycles the driver’s heat valve. The fan speed is
and displays the revision number of the display. In about controlled by setting the DEF slide control at the left of the
30 to 60 seconds the A/C system should start up. display to the desired position. The lowest fan speed is
To turn the system off, press the I/0 key on the display. 30%. When the system is operating in reheat, the driver
Pressing the I/0 key again will restart the system. liquid solenoid valve is opened, the heating valve cycles
and the compressor and condenser fan motors are
OPERATIONAL CONTROLS energized.

Temperature Control Defrost Windshield

Temperature is controlled by cycling the main and To initiate defrost, set the HEAT and DEF slide
driver’s heat valve and unloading the compressor controls to high, press the RECIRC/FRESH AIR key
twice to open the ram air dampers.
The compressor cylinder unloader requirement (two,
four, or six) is determined by the cooling requirements of Humidity Control
the passenger compartment. Humidity control is activated when the humidity is
greater than 50% and deactivated at 45%.
Passenger Compartment Control
The compressor is fully loaded (6 cylinders) to
The passenger compartment is controlled by
subcool the air and then the air is reheated.
maintaining the average return air temperature of the
curbside and roadside evaporators. The default Heating
temperature is 72_F (22_C). In the heat capacity state, the A/C system is shut
If cooling is required for the main compartment, the down provided no compartments are calling for cooling.
compressor and condenser will start, the main and The heating capacity is controlled by varying the cycling
driver’s compartment liquid solenoid valve will open and of the heat valve. The controller automatically calculates
the heat valve in the main evaporator will close. the time, based on a 20 second period.

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 Date March 2003 Page 16A-21

Auxiliary Heater Control 1. Compressor Unloader Bank A. At ambient

The auxiliary heater is circuited to the engine to temperatures below 92_F (33_C), when the
ensure correct engine temperature. It is internally discharge pressure increases above 300 psig (1.7
controlled by the heater’s thermostat. The auxiliary mPa), the first compressor unloader is energized.
heater switch is located on the left side console. When This output will remain energized until the pressure
the engine is off, pushing the auxiliary heater switch decreases below 265 psig (1.5 mPa).
forward activates the 90 minute timer in the Proheat unit. At temperatures above 92_F, (33_C) when the
To turn the heater off, push the switch back. It will purge discharge pressure increases above 340 psig (2.0
for 2 to 3 minutes. If the coach is started during mPa), the first compressor unloader is energized.
preheating, the temperature-dependant control This output will remain energized until the pressure
overrides the timer. decreases below 300 psig (1.7 mPa). The system
returns to low temperature operation when the
Coolant Boost Pump Control temperature reaches 87_F (30_C).
The coolant boost pump output is energized when 2. Compressor Unloader Bank B Relay. Does not
the main heat valve has been opened for 60 seconds or unload by discharge pressure.
when the driver’s heat control is set above 10%. Once
energized, the boost pump output is de-energized when Condenser Fan Speed Control
the heat valve percentage is less than 20% for fifteen The first condenser fan motor is energized when the
minutes and the driver’s heat control is less than 5% for compressor clutch output is energized. The second
15 minutes. condenser fan is energized when the clutch is energized
and is based on compressor discharge pressure. The
Compressor Unloader Control fan speeds are then controlled by discharge pressure.
The unloader outputs control the compressor The second condenser fan motor is energized when
capacity by energizing or de-energizing unloader the clutch is energized and the discharge pressure
solenoid valves to deactivate the compressor cylinders increases above 175 psig (1.2 mPa). It will be
in pairs. When the compressor is off, the unloaders are de-energized when the clutch is de-energized or the
de-energized immediately. discharge pressure decreases below 125 psig (0.861
To reduce horsepower consumption on the engine, mPa).
the unloaders are energized when full cooling is not The condenser fans are started in low speed and will
required. remain in low speed until the discharge pressure
increases above 225 psig (1.6 mPa). The fans will remain
a.) Suction Pressure
in high speed until the discharge pressure decreases
In addition to temperature control, the electric
below 165 psig (1.1 mPa).
unloaders will be used to prevent coil frosting:
1. Compressor Unloader Bank A. When the suction Staging
pressure decreases below 25 psig (172 kPa), the When the system is started, the condenser and
first unloader is energized, unloading the first evaporator fans are staged “on” to reduce the total
compressor cylinder bank (two cylinders); this starting current. Staging is given in Table 12 below:
output will remain energized until the pressure
increases to above 32 psig (221 kPa). TABLE 12. Main Compartment Staging
2. Compressor Unloader Bank B. When the suction Time
Ref. Controller Action
pressure decreases below 21 psig (145 kPa), the (seconds)
second unloader is energized, unloading the Time 0 0 Main Evaporator Fans Low
second compressor cylinder bank (two cylinders).
Time 2 Time 0 + 2 Main Evaporator Fans High
This output will remain energized until the pressure
increases to above 28 psig (193 kPa). Time 3 Time 0 + 4 Condenser Fan 1 Low
Time 4 Time 3 + 1 Condenser Fan 2 Low
b.) Discharge Pressure
Head pressure is also controlled by the unloaders: Time 5 Time 3 + 3 Both Condenser Fans High

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 16A-22

Compressor Clutch Control An exception to the above is that there is a five minute
A belt-driven electric clutch transmits engine power to delay to open RAM air once it is closed in the auto mode.
the air conditioning compressor. De-energizing the There is no delay to close RAM air.
clutch removes power from the compressor. The clutch
will be engaged whenever passenger compartment is in
b.) Display Override
cooling. The clutch will be disengaged when the system Press the recirc key to toggle both ram air dampers
is off, when passenger compartment is in heating or from AUTO to closed, open, then return to AUTO.
during high or low pressure alarm conditions or when in Pull-up and Pulldown Modes
vent mode. The clutch coil is controlled by the main Pull-up and pulldown modes operate at start up only
controller. to override normal temperature control in the passenger
The compressor is prevented from operating when compartment to reach the desired temperature rapidly.
the ambient temperature is below 32_F (0_C). Once the controller exits this mode, the controller does
The clutch coil will be de-energized if the discharge not enter the mode again until it is restarted. Set the
pressure rises to 385 psig (2.6 mPa), the setting of the driver’s 2 slide controls beside the display for maximum
compressor-mounted high pressure switch. The clutch fan speed and corresponding heat setting.
coil will energize when the discharge pressure falls to When pull-up and pulldown modes are not active,
285 psig (2.0 mPa). normal temperature control determines fan speed,
The clutch coil will be de-energized if the suction unloading and heat valve states.
pressure decreases below 6 psig (41 kPa).
Input Processing
Parcel Rack Evaporators (Optional) The system determines correct operation by reading
The temperature is controlled by a thermostat on the the temperature sensors (thermistors), the pressure
roadside evaporator assembly. The parcel rack solenoid transducers or the humidity sensor. Refer to
valve is located in the condenser module. “Specifications” for electrical specifications for input
A switch on the driver’s left dash controls the devices and “Components” for functional descriptions.
operation.
Diagnostics
NOTE: The parcel rack A/C will not operate unless Self tests (diagnostics) are automatically executed
the main A/C system and parcel rack blowers are in when the system is powered up.
operation.
Alarm Description
Alarm descriptions and troubleshooting procedures
RAM Air Control are provided in the troubleshooting subsection later in
At power up, the passenger ram air is auto controlled this manual. (See Table 18, page 16A-46.)
by the passenger return air temperature and ambient
temperature. Use the fresh air/recirc Key to manually Hour Meters
override. An hour meter records the compressor run-time
hours. The maximum hours is 999,999.
a.) Auto Mode
An hourmeter records the total time the controller is
1. If the passenger’s return air temperature is greater
operating in hours. The maximum hours is 999,999.
than ± 2_F (1_C) from the passenger thermostat
setting, the passenger and driver’s RAM air will be Communications (Driver Display - Controller -
closed if the ambient is above 50_F (10_C) or Coach Datalink)
relative humidity is above 55%. The communications link from the controller to the
2. Otherwise, the RAM air is open. display is RS-232.

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 Date March 2003 Page 16A-23

MAINTENANCE
Observe the following warnings when providing maintenance on the heating and air conditioning system:

WARNING

1. When servicing the unit, use caution when handling R-134a. These refrigerants, when in
contact with high temperatures (about 1000°F), will decompose into highly corrosive and
toxic compounds.
2. Avoid refrigerant coming in contact with the eyes. Should refrigerant come in contact with
the eyes, wash eyes for minimum of 15 minutes with potable water only. THE USE OF
MINERAL OIL OR REFRIGERANT OILS IS NOT RECOMMENDED.
3. Avoid having refrigerant contact the skin. Should refrigerant contact the skin, treat it as if the
skin had been frostbitten or frozen.
4. Be sure ventilation in the workspace is adequate to keep the refrigerant concentration below
1000 parts per million. If necessary, use portable blowers.
5. Beware of rotating fan blades and unannounced starting of fans.
6. Do not use a nitrogen cylinder without a pressure regulator.
7. Do not use oxygen in a refrigeration system, as an explosion could occur.
8. Never fill a refrigerant cylinder beyond its rated capacity. The cylinder may rupture due to
excessive pressure when exposed to high temperatures.
9. When starting the unit, be sure that all manual refrigerant valves in the discharge line are
open. Severe damage could occur from extremely high refrigerant pressures .
10. Always wear safety glasses.
11. Keep hands, clothing and tools clear of the evaporator and condenser fan.
12. No work should be performed on the unit until all circuit breakers and start-stop switches in
the engine and electrical compartments are turned off, and power supply is disconnected
and locked in the OFF position.
13. Always work in pairs. Never work on the equipment alone.
14. In case of severe vibration or unusual noise, stop the unit and investigate.
15. Beware of unannounced starting of the evaporator and condenser fans. Do not open the
condenser fan grille or evaporator access panels before turning power off, and
disconnecting and securing the power plug.
16. Be sure power is turned off before working on motors, controllers, solenoid valves and
electrical control switches. Tag circuit breaker and power supply to prevent accidental
energizing of circuit.
17. Do not bypass any electrical safety devices, e.g. bridging an overload, or using any sort of
jumper wires. Problems with the system should be diagnosed, and any necessary repairs
performed by qualified service personnel.
18. In case of electrical fire, turn battery disconnect switch to OFF position.
19. Prior to any welding, read and follow the instructions in the Welding Caution on page Intro-2
and on the coach-mounted decals.

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 16A-24

MAINTENANCE SCHEDULE
SYSTEM REFERENCE
OPERATION
ON OFF SECTION
a. Daily Maintenance
X Pre-trip Inspection - after starting “Pre-trip inspection” in “Operation”
X Check the tension and condition of the V-belt (not when the None
engine is running)
b. Weekly Inspection
X Perform daily inspection See “a. Daily Maintenance” above
X Check condenser, evaporator coils & air filters for cleanliness None
X Check refrigerant hoses and compressor shaft seal for leaks “Refrigerant leak check” below
X Feel filter-drier for excessive temperature drop across drier “Filter-drier” below
c. Monthly Inspection and Maintenance
X Perform weekly inspection and maintenance See “b. Weekly Inspection” above
X Clean evaporator drain pans and hoses None
X Check the wire harnesses for chafing and loose terminals Replace/Tighten
X Check the fan motor bearings None
X Check the compressor mounting bolts for tightness None
X Check the fan motor brushes None

With the valve stem midway between frontseated and

backseated positions, the suction or discharge line is
SUCTION AND DISCHARGE SERVICE open to both the compressor and the gauge connection.
VALVES
The suction and discharge service valves (Figure 16)
used on the compressor are equipped with mating To Discharge or Valve Cap
flanges for connection to flanges on the compressor. from Suction Line
These valves are provided with a double seat and a
gauge connection, which allows servicing of the
compressor and refrigerant lines.
Turning the valve stem counterclockwise (all the way
out) will backseat the valve to open the suction or
discharge line to the compressor and close off the Valve
Port to Gauge
gauge connection. In normal operation, the valve is Connection Stem
backseated to allow full flow through the valve. The valve Compressor
should always be backseated when connecting the
service manifold gauge lines to the gauge ports. Service Valve Service Valve
Turning the valve stem clockwise (all the way forward) Frontseated Backseated
will frontseat the valve to close off the suction or (clockwise) (counterclockwise)
discharge line to isolate the compressor and open the
gauge connection.
To measure suction or discharge pressure, midseat
the valve by opening the valve clockwise 1/4 to 1/2 turn. FIGURE 16. Suction or Discharge Service Valve

MOTOR COACH INDUSTRIES

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 Date March 2003 Page 16A-25

AIR FILTERS 4. Wash in warm water, if excessively dirty use a mild

The entire air supply of the coach passes through filter laundry detergent in warm water, let dry and
assemblies located in the main evaporator and driver’s reinstall.
HVAC modules. The main filter is removable and should
be periodically replaced. The drivers filter should be MANIFOLD GAUGES
cleaned regularly. Use the following procedures to A manifold gauge set must be installed to determine
remove and replace filters. operating pressures, charge, equalize or drain the
system. Operating pressures may also obtained from
NOTE: During dusty conditions, check main air filters diagnostics on the driver’s display.
every two weeks. Replace or clean as required.
Gauge Installation -- Compressor

CAUTION Low Pressure

Gauge
High Pressure
Gauge
(Suction) (Discharge)
The coach should never be operated with-
out the main filter assemblies. Operating
without a filter will eventually plug the evap-
orator coil and seriously reduce heating
and cooling. A C B Hand Valve
Hand Valve
(Backseated) (Frontseated)
Main Filter Assembly A. Connection to C. Connection to Either:
1. Open the battery compartment door on the Low Side of System Vacuum Pump
curbside of the coach. Refrigerant Cylinder
B. Connection to Oil Container
High Side of System Evacuation Line
FIGURE 18. Manifold Gauge Set
1. Remove the protective caps from the service valve
stems and ports.
2. Ensure that both valves are fully backseated.
3. Connect the high side hose tightly to the discharge
service valve port.
4. Connect the low side hose loosely to the suction
service valve port.
5. Loosen the charging hose at the gauge set’s
dummy fitting.
6. Frontseat both gauge valves.
7. Open the discharge service valve by turning it
FIGURE 17. Filter Access Door counterclockwise 1/4 to 1/2 turn.
8. Slowly open the manifold discharge valve
2. Open the filter access door and remove top filter
approximately 1 turn.
first, slide bottom filter up and then remove.
9. Tighten the charging hose onto the dummy fitting
3. Replace filter material and reinstall.
once air has been purged from the hose.
Driver’s Filter Assembly 10. Slowly open the manifold suction valve to remove
1. Remove front lower dash panel and inner module air from the line.
cover. 11. Frontseat (close) both manifold valves.
2. Unfasten filter clips and remove filter. 12. Open the suction service valve counter- clockwise
3. Shake out excessive dirt and grit. approximately 1/4 to 1/2 turn.

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 Date March 2003 Page 16A-26

CHECKING FOR NON-CONDENSABLE NOTE: When you pump down the refrigerant system,
1. With the engine off, stabilize the system at a certain parts may frost. Allow the parts to warm to
constant temperature for several hours to equalize ambient temperature before opening the system to
the pressure between the suction and discharge avoid internal condensation and moisture in the
sides of the system. system.
2. Check the temperature at the condenser. 7. Reconnect suction transducer connector.
3. Check the pressure at the compressor discharge Components on the low side of the system may now
service valve. be serviced.
4. Check the saturation pressure as it corresponds to Refrigerant Removal
the condenser temperature. (See
Temperature-Pressure Chart) NOTE: By law, refrigerant must be recovered.
5. If the gauge reading is 3 psig (21 kPa) or more than 1. Pump down the system.
the calculated P/T pressure in Step 4, 2. Connect a refrigerant recovery system to the
non-condensables are present. condenser service valve to remove the refrigerant
6. Remove the refrigerant using a refrigerant recovery charge. Refer to the instructions provided by the
system. (See Refrigerant Removal.) manufacturer of the refrigerant recovery system.
7. Evacuate and dehydrate the system. (See 3. Remove the refrigerant.
Evacuation and Dehydration)
NOTE: Before opening any part of the system, the
8. Charge the unit (See Charging the System.) gauge should indicate a slight positive pressure.

SYSTEM PUMP DOWN AND CHARGING NOTE: When you pump down the refrigerant system,
certain parts may frost. Allow the parts to warm to
System Pump Down ambient temperature before opening the system to
avoid internal condensation and moisture in the
NOTE: To avoid damage to the earth’s ozone layer, system.
use a refrigerant recovery system whenever removing
refrigerant. By law, refrigerant must be recovered.
Refrigerant Leak Check
Perform a leak check after opening the system.
To service or replace the filter-drier, expansion valve,
evaporator coils, condenser or suction line, pump the NOTE: Only nitrogen may be used to pressurize the
refrigerant into the condenser coil. system.
1. Install the manifold gauge set. 1. Ensure that the main liquid line and driver solenoid
2. Frontseat the filter drier inlet valve by turning it valves are open.
clockwise.
NOTE: Instructions #2 and #4 are for U.S.A. only. In
3. Unplug connector from suction transducer. Canada, it is illegal to use refrigerant for leak
detection. Fines are considerable.
NOTE: The following procedure may have to be
repeated several times to maintain the 1 psig (6.9 kPa) 2. If system is without refrigerant, add enough
pressure, depending how much refrigerant is refrigerant to build up pressure to between 30 to 50
absorbed in the oil. psig.
3. Add sufficient nitrogen to raise the system pressure
4. Start the system and run it in cooling. to 150 to 200 psig.
5. Stop the unit when the suction pressure reaches 1 4. Check for leaks with electronic refrigerant leak
psig to maintain a slight positive pressure. detector (or soap solution for nitrogen fill).
5. Remove the refrigerant using a refrigerant recovery
6. Frontseat (close) the suction service valve to trap
system, and repair any leaks.
the refrigerant between the compressor suction
service valve and the filter drier inlet valve. The low 6. Evacuate and dehydrate the system.
side of the system should be at 1 psig and ready for 7. Charge the unit.
servicing. 8. Ensure that the system operates normally.

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 Date March 2003 Page 16A-27

Evacuation and Dehydration 4. Ensure that the manifold vacuum gauge valve is
The presence of moisture in a refrigeration system closed and that the vacuum pump valve is open.
can have many undesirable effects. The most common 5. With the compressor service valves closed
are copper plating, acid sludge formation, “freezing-up” (backseated) the vacuum pump and thermistor
of metering devices by free water, and formation of acids valves open, start the pump and draw the manifold
resulting in metal corrosion. and hoses into a deep vacuum. Shut the pump off
NOTE: Using a compound gauge for determination and see if the vacuum holds. This is to test the setup
of vacuum level is not recommended because of its for leaks.
inherent inaccuracy. Evaluate and dehydrate only 6. Midseat the service valves.
after pressure leak test.
7. Open the main and driver’s solenoid valves to
NOTE: A vacuum pump with a minimum ensure vacuum through the whole system.
displacement of 5 cfm and a good electronic vacuum 8. Start the vacuum pump and slowly open the
indicator/micron gauge are required. vacuum pump valve halfway.
NOTE: Ambient temperature must be above 60_F. If 9. Open the vacuum gauge valve.
the ambient temperature is less than 60_F the
moisture may freeze in the system. As required, use NOTE: Instructions 10 to 14 inclusive are for U.S.A.
heat lamps, heat blankets or other methods to raise only. In Canada, it is illegal to break vacuum with
the ambient temperature. refrigerant. Fines are considerable.
This procedure should be used after any system
repair. 10. Evacuate the unit until the vacuum gauge indicates
1. Remove the refrigerant using a refrigerant recovery 1500 microns Hg vacuum.
system.
11. Close the gauge valve, the vacuum pump valve,
2. Replace the filter dryer before evacuation. and stop the vacuum pump.
3. Attach three hoses from the manifold (Min. 3/8”
12. Break the vacuum with clean dry nitrogen or R134a
OD), one to the condenser service valve (Figure
refrigerant.
19), the others to the compressor suction and
discharge valves. 13. Raise the system pressure to approximately 2 psig.
Monitor the pressure with the compound gauges.
14. Remove the refrigerant using a refrigerant recovery
system or release nitrogen to atmosphere.
15. Start the vacuum pump and open all valves.
Evacuate the unit to 500 microns Hg vacuum.
SERVICE VALVE
16. Close off the pump valve.
17. Isolate the vacuum gauge and stop the pump.
Wait for 5 minutes to see if the vacuum holds. (If
vacuum rises, it indicates that there is a leak or that
moisture remains in the system. If the pressure
stays below 2500 microns in the 5 minute period,
the system is tight and dry.) If not, perform a leak
test and repair as required.
18. Close the micron gauge valve.
19. With a vacuum still in the unit, charge the system
from a refrigerant container on a scale. Refer to
specifications for refrigerant charge.

NOTE: If the system has been open to the air for a

long time, or a major system repair has been
FIGURE 19. Condenser Service Valve performed, repeat steps 10 to 14.

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SYSTEM CHECKS NOTE: The system is properly charged when there

are no bubbles present in the main liquid line sight
Checking the Refrigerant Charge glass.
1. Start the coach.
2. Set fast idle, activate cooling and wait 15 minutes.
7. Add or remove refrigerant as required.

NOTE: The head pressure must be at least 150 psig

Partial Charge
(1.03 mPa) for R-134a systems.
1. Start the coach.
3. As required, block the condenser air flow to raise 2. Set fast idle, activate cooling and wait 15 minutes.
the head pressure.
4. Check the main liquid line sight glass, if no bubbles
NOTE: The head pressure must be at least 150
are present the system is properly charged. Add or
psig (1.03 mPa) for R-134a systems.
remove refrigerant charge to the proper level.

Full Charge 3. As required, block the condenser air flow to raise

the head pressure.
1. Evacuate and dehydrate system. 4. Run the unit in cool mode for 15 minutes.
2. Place the appropriate refrigerant cylinder on a scale
5. With the suction service valve midseated, remove
and connect the charging hose from the container
air from hose at the refrigerant cylinder.
to the condenser service valve. Remove air from the
hoses. 6. Open the cylinder valve and add a vapor charge
until there are no bubbles present in the main liquid
3. Note the combined weight of the refrigerant and
line sight glass. Add or remove refrigerant until the
container.
proper level is achieved.
4. Open the liquid valve on the refrigerant container.
Midseat the filter-drier inlet valve and allow
refrigerant to flow into the unit. (See
SPECIFICATIONS for the correct charge.)
CAUTION
5. When the drum weight (scale) indicates that the
The level should NOT appear in the upper
correct charge has been added, close the liquid line sight glass, as an overcharge could occur.
valve on the drum and backseat the condenser
service valve.
6. Run the coach engine at high idle speed in cooling 7. Backseat the suction service valve. Close the vapor
mode for at least 15 minutes with the head pressure valve on the refrigerant drum and record the weight.
at least 150 psig for R-134a. Replace all valve caps.

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High Pressure Switch Check 4. Set the nitrogen pressure regulator higher than the
cutout point on the switch being tested (See
Specifications.)
WARNING 5. Open the cylinder valve. Slowly open the regulator
valve to increase the pressure until it reaches the
cutout point. The switch should open, which is
Do not use a nitrogen cylinder without a pres- indicated by an infinite reading on an ohmmeter.
sure regulator. Do not use oxygen in or near a
refrigeration system, because an explosion 6. Close the cylinder valve and release the pressure
may occur. through the bleed-off valve. As the pressure drops
to the cut-in point, the switch contacts should close,
indicating no resistance on the ohmmeter.
1. Disconnect wiring and remove the switch from the 7. Replace switch as required.
unit.
High Pressure Switch Installation
NOTE: All units have Schraeder valves at the high 1. Disconnect wiring and remove the defective switch
pressure switch connection. from the unit.
NOTE: All units have Schraeder valves at the high
2. Connect an ohmmeter across the switch terminals. pressure switch connection.
The switch is good if the ohmmeter indicates no
resistance. 2. Test new switch (See Checking the High Pressure
3. Connect the switch to a cylinder of dry nitrogen Switch.)
(Figure 20). 3. Install the new high pressure switch.
4. Reconnect the wiring.
Filter Dryer Inspection
1
With the system running, check for a restricted or
4 plugged filter-drier by feeling the filter drier’s liquid line
inlet and outlet connections. If the outlet side feels cooler
2 5 1. Cylinder Valve than the inlet side, change the filter-drier.
and Gauge
2. Pressure Regulator Filter Dryer Replacement
3. Nitrogen Cylinder
4. Pressure Gauge 1. Turn engine off.
3 6
(0 to 400 psig = 2. Close filter dryer inlet valve.
0 to 2.8 mPa)
5. Bleed-Off Valve
3. Pump down the system.
6. 1/4 inch Connection 4. Replace the filter-drier.
5. Evacuate and dehydrate.
6. Open dryer inlet valve to refill system and check for
leaks.
FIGURE 20. High Pressure Switch Test 7. Check the refrigerant level (See Checking the
Refrigerant Charge.)

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Thermal Expansion Valves Inspection The driver’s display may also be used to show
The thermal expansion valves require no regular compressor pressures.
service. If the system is not cooling sufficiently and the 8. Start the coach and run it on fast idle until the unit
compressor crankcase is cool to the touch, the thermal has stabilized, about 20 to 30 minutes.
expansion valves may be inoperative. The system
9. Heat up the interior of the coach, then set
superheat must be checked.
temperature to lowest value to induce a pulldown.
Superheat Measurement Use high idle.
NOTE: Ambient temperature should be above 70 _F 10. From the temperature/pressure chart, find the
(21 _C). saturation temperature corresponding to the
evaporator outlet pressure. (See Table 16.) Add an
1. Remove the evaporator access door in the estimated suction line loss of 2 psig (13.8 kPa) to the
condenser compartment. number.
2. Remove the Presstite insulation from the expansion 11. Record the temperature of the suction gas at the
valve bulb and suction line. expansion valve bulb.
3. Loosen one bulb clamp and ensure that the area 12. Subtract the saturation temperature determined in
under clamp (above the bulb) is clean. Step 11. from the temperature measured in step 12.
4. Place a temperature thermocouple in contact with The difference is the superheat of the suction gas.
the suction tube and parallel to the TXV bulb 13. Repeat step 10, 11, 12, six times at three minute
5. Secure the loosened clamp, ensuring that both bulb intervals during pulldown and determine the
and thermocouple are firmly secured to the suction average superheat from the six readings.
line. 14. The average superheat should be 5 to 10_F for the
6. Reinstall the insulation around the bulb. driver’s and parcel rack valves. The average
7. Install a manifold gauge set. with an accurate low superheat should be 15 to 25 _F for the main
pressure gauge to the service port on the suction expansion valve. Replace the expansion valve if the
service valve, (See Manifold Gauge Installation.) superheat is out of range.

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Expansion Valve Removal Expansion Valve Installation

1. Pump down the low side of the unit (See System
NOTE: Superheat on expansion valves is factory set.
Pump Down.)
Do not adjust.
2. Remove the insulation from the expansion valve
bulb. 1. Using new gaskets, install the new cage and power
3. Loosen the retaining straps holding the bulb to the head assemblies provided with repair kit
suction line and detach the bulb from the suction 2. Install the thermal bulb on the suction line after first
line.
cleaning the mating surface. Use clean heat
4. Loosen the flare nuts on the equalizer line and transfer paste between bulb and suction line.
disconnect the equalizer line from the expansion
3. Strap the thermal bulb to the suction line at 4 o’clock
valve.
or 8 o’clock position.
5. Remove the capscrews and lift off the power head
and cage assemblies and gaskets. 4. Ensure that the straps are tight.
6. Check, clean and remove any foreign material from 5. Insulate the bulb and suction line.
the valve body, valve seat and mating surfaces. 6. Connect the equalizer line to the expansion valve.
7. Evacuate and dehydrate the system (See
1 Evacuation and Dehydration.)
8. Open the condenser service valve and all service
5 valves.
3 4
2 9. Run the coach for 30 minutes on fast idle.
6 10. Ensure that the system is properly charged (See
Charging the System.)
11. Ensure superheat is within proper range (See
1. POWER ELEMENT 11 Superheat Measurement.)
2. CAP - SEAL NUT 7
3. BONNET - SEAL (FLARE)
4. PACKING NUT
5. ADJUSTING STEM
AND PACKING ASSY 6
6. GASKET 8
7. CAGE ASSEMBLY
8. GASKET
9. BODY FLANGE
10. CAPSCREW
9
11. REMOTE BULB
10

4194

FIGURE 21. Expansion Valve

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 Date March 2003 Page 16A-32

CONDENSER
Removing the Condenser
NOTE: The condenser assembly module must be
removed from the coach to service the condenser
coil.

MAIN LIQUID REFRIGERANT LINE

PARCEL RACK LIQUID REFRIGERANT LINE

FANS
SERVICE VALVE
(CONNECTS MANIFOLD GAUGES)

CONTROLLER CONNECTION

FILTER / DRYER

ACCESS PANELS
REFRIGERANT
SIGHT GLASS

POWER STUD
CONDENSER FAN STUD
CONTROL BOX
CONDENSER END VIEW
(Behind Access Panels)
SIGHT GLASS VIEWING PORT

REAR BAGGAGE BAY

(Left Hand Road Side View)

FIGURE 22. Condenser Removal

1. Remove two side access panels from rear of the last 7. Remove front panel and the eight screws fastening
baggage bay. condenser to frame (See Figure 23.).
2. Remove and reclaim the entire refrigerant charge. 8. Remove the stabilizing bracket on the top of the
condenser unit (See Figure 23.).
3. Turn main battery disconnect switch to OFF position
and lock. 9. Remove eight screws fastening condenser door
hinges to frame. Remove condenser.
4. Disconnect all electrical leads to the module.
10. Remove condenser module by sliding out on
5. Disconnect refrigerant lines to the module. (See mounting rails onto a lift table. Take care that the
Figure 22.) refrigerant piping does not catch on the side of the
6. Remove door latch studs (See Figure 23.). coach frame.

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Servicing the Condenser Coil

1. Remove the side panel (with control box).
STABILIZING BRACKET
2. Remove the roof and panel assemblies.
3. Unbraze the coil/tubing connections and roll the
front module assembly forward to provide
DOOR LATCH
clearance for coil removal.
4. Remove the condenser coil.
5. Repair or replace the condenser coil.
DOOR HINGES
Condenser Module Installation
Re-install the condenser coil by performing the above
procedure in reverse order.

Servicing the Condenser Electrical Box

1. Remove the service panel on the bottom roadside of
baggage bay #3.
2. Remove the capscrews on the electrical control box
FIGURE 23. Condenser Removal to access the control relays.

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 Date March 2003 Page 16A-34

MAIN EVAPORATORS 6. Remove the motor mounting channel and place it

on a workbench.
7. Remove the blower housing and venturi on one side
and the venturi on the other side.
8. Remove the motor and blower wheel assembly by
sliding it out of the remaining blower housing.
9. Repair or replace defective component(s) as
required.
Remove Main Evaporator Module
NOTE: Access the Evaporator and Heater Coil
Assembly by opening and removing the access door
located in the #3 Baggage Compartment. Slide the
hinge pins out of the pin brackets. See Figure 25.

EVAPORATOR REAR VIEW

DOOR HINGES
LOW SIDE PORT
ACCESS HOLE

ACCESS DOOR ---

EVAPORATOR FRONT VIEW MAIN EVAPORATOR
HEATER COIL COMPARTMENT
(Right Hand Curb Side View)

FIGURE 24
Servicing the Main Evaporator Motor Brushes FIGURE 25: Evaporator/Heater Coil Access Door
1. Turn main battery disconnect switch to OFF and
1. Pump down the low side of the HVAC system. (Refer
lock it.
to System Pumpdown.)
2. Remove the wires and base mounting screws.
2. Turn the main battery disconnect switch to OFF and
3. Change the two brushes at the front of the motor. lock it.
4. Rotate the motor to access the two rear brushes. 3. Close the glycol hand valves located in the engine
Servicing the Main Evaporator Motors compartment. (Figure 26)
1. Turn the main battery disconnect switch to OFF and 4. Remove the p-clips and detach the harness from
lock it. the Right Hand Blower Air Duct (3 p-clips in total).
2. Remove the drain pan. 5. Disconnect all electrical connections to the Blower
3. Disconnect the electrical connections. Motors, Evaporator and Heater Coil Assembly.
4. Remove the four motor rail mounting nuts (Figure 6. Remove the Left Hand and Right Hand Ducts from
24). the Blower Housings.
5. Remove the sealant from between the motor rail 7. Remove the Evaporator Motor and Blower
and the evaporator housing. Assembly.

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 Date March 2003 Page 16A-35

PARCEL RACK EVAPORATOR

RETURN VALVE
Parcel rack evaporators are located in parcel rack
Flow Open compartment #4 on the roadside and #5 on the
curbside.
Servicing Brushes
1. Turn the main battery disconnect switch to OFF and
lock.
2. Remove the two brush caps and replace inside
brushes with new brushes.
Motor Removal
Flow SUPPLY VALVE
1. Remove the two nuts attaching the motor mount to
closed
the stabilizing bracket.
2. Remove the five fasteners attaching the blower
housing to the evaporator compartment.
FIGURE 26: Return and Supply Valves 3. Disconnect the motor wires from the connector.
8. Drain the engine coolant from the Heater Coil. drain 4. Remove the blower and motor assembly.
is located on the lower coolant tube assembly on 5. Loosen the blower wheel from the motor shaft.
the LHS of the Heater Coil. 6. Remove the two bolts from the motor mount and
9. Disconnect the silicone coolant hoses and clamp at remove the motor.
the evaporator.
10. Remove the remaining refrigerant (refer to Removal of Parcel Rack Evaporator Coil
Removing the Refrigerant Charge). 1. Pump down the refrigerant system. (See Pump
11. Disconnect the refrigerant lines to the evaporator Down.)
assembly. 2. Remove the side access panel.
12. Plug up the refrigerant line outlets (the copper 3. Disconnect expansion valve thermal bulb attached
tubes). to the 7/8-inch copper tube.
13. Remove the refrigerant tube support bracket 4. Disconnect 7/8 and 3/8-inch copper lines.
assembly on RHS wall fo Evaporator compartment. 5. Lift evaporator coil up and push towards the rear for
14. Remove the door latch brackets located on the removal.
bottom of the LH and RH sides of the Evaporator
Compartment walls.
15. Remove the Access Door Frame Assembly
(requires removal of 31 - #8 screws around the
perimeter of the Frame Assembly).
16. Remove the Evaporator and Heater coil assembly
from the coach through the access door.
Install the Evaporator
Re-install the evaporator module by performing the
removal procedure in reverse order.

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DRIVER’S CONTROL BOX

The driver control box is located behind the return air
panel, below the passenger side dash and under the
right headlight (Figure 27). Remove the return air panel
by removing the eight wingnuts holding the panel in
place.

Driver’s Control Box Removal

HEADLIGHT

DRIVER FIGURE 28. Driver Evaporator

CONTROL
BOX 2. Using a flat screwdriver, unfasten the three 1/4 turn
fasteners from the access cover on the driver
evaporator assembly.
3. Open the driver storage compartment and remove
the plastic plug in the sheet metal.
4. With a screwdriver, unfasten the last 1/4 turn
fastener.
5. Draw the access cover towards the rear, and slide it
to the right.
FIGURE 27. Removing the Driver’s Control Box Blower Removal
1. Disconnect the Packard plug from the blower.
1. Turn main battery disconnect switch to OFF and 2. Undo the latch and push the blower towards the
lock it. rear.
2. Remove the power wire from the power stud and the 3. Drop the blower down and remove it.
connector from the box. Air Filter Removal
3. Remove the 1/4-inch capscrew at the upper right 1. With the access cover removed, slide the right-
cover of the box. Pull the box laterally approximately hand side air filter towards the center and turn the
3/4-inch to the right to remove it from the pocket. right corner past the edge.
4. Rotate box counterclockwise 90 degrees as shown 2. Slide the left-hand side filter to the right and repeat
in Figure 27 and carefully lift the box out. as above.
3. Clean the filter and reinstall.
5. Repair or replace defective components as
necessary. Heater Core Removal
1. Shut off the ball valve located under the driver’s floor
Driver’s Control Box Installation in the service compartment.
Re-install the driver control box by reversing the 2. Clamp off the silicon hose to close the heater core’s
above procedure. input and output.
3. Disconnect hose clamps and separate the hose
DRIVER’S EVAPORATOR from the fitting.
4. Remove the screws that attach the heater core to
Remove Driver’s Evaporator Components the unit.
Removing the Evaporator Coil Assembly
Access Cover Removal 1. Pump down the refrigerant system. Refer to
1. Remove the stepwell access cover and disconnect “Pumping the System Down” earlier in this
the 2-inch flex hose adapter (Figure 28). subsection.

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2. Disconnect the liquid line solenoid valve Packard the spare tire compartment and is located on a 4-inch
plug. (102 mm) diameter tube under the driver’s seat.
3. Disconnect the expansion valve thermal bulb 1. Disconnect the Packard plug.
attached to the 7/8-inch copper tube. 2. Remove the No. 10 screw attached to the damper
4. Disconnect the 7/8 and 3/8-inch copper lines. arm, and snap the damper operator out of its clip.
5. Lift the evaporator coil up and push it towards the DUCT CLEANING
rear for removal.
Return air ducts have covered access locations in
Checking RAM Air Actuator Operation baggage bay#3 for cleaning (Figure 29). Use a long
1. With the coach running, press the VENT key to vacuum hose to clean out these ducts. Supply air ducts
open the ram air valves. inside the coach have 2 access locations each on curb
2. Check for power at the Packard plug. and road side within the coach.
3. If power exists at the Packard plug, plug in the
actuator.
4. The actuator should extend 5/8” and get warm
quickly if it is operating correctly.
Driver’s RAM Air Actuator Removal
The driver’s RAM air actuator is located at the lower
right-hand side of the driver’s evaporator unit.
1. Remove the No. 10 screw attached to the damper
arm, and snap the damper operator out of its clip.
2. Follow the removal instructions in reverse order.

PASSENGER RAM AIR ACTUATOR

Passenger RAM Air Actuator Removal
The passenger RAM air damper is accessible through FIGURE 29

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 Date March 2003 Page 16A-38

COMPRESSOR 3. Immerse the common connection of the gauge

manifold in an open container of refrigeration oil.
Add Compressor Oil
4. Remove air from the lines.
NOTE: See specifications to determine correct oil 5. Unplug suction pressure transducer.
type. 6. With the unit running, frontseat (clockwise) the
suction service valve and pull a vacuum in the
Oil may be added to the compressor with an oil pump
compressor crankcase.
or the closed system method.
7. Slowly crack the suction gauge manifold valve and
Oil Pump Method oil will flow through the suction service valve into the
1. Mount a Robinair 14388 pump to a refrigeration oil compressor.
container. 8. Add oil as required.
NOTE: Ensure that the compressor oil container 9. Reconnect suction pressure transducer.
does not remain open to air for any length of time.
Remove Compressor Oil
2. Backseat the suction service valve and connect the 1. Frontseat the suction service valves and pump the
oil charging hose to the port. unit down to 3 to 5 psig.
3. Crack open the service valve and remove air from 2. Frontseat the discharge service valve.
the oil hose at the oil pump. 3. Reclaim any remaining refrigerant from compressor
4. Add oil as required. crankcase.

Closed System Method NOTE: If the oil drain plug is not accessible, it will be
1. In an emergency where an oil pump is not available, necessary to extract oil through the oil fill plug with a
oil may be drawn into the compressor through the siphon tube.
suction service valve.
NOTE: Special care must be taken when working
with POE oil that is used with HFC refrigerants such as WARNING
R124a, as POE oil will easily absorb water. Do not
leave POE oil containers open to the atmosphere. Extreme care must be taken to ensure that all
the refrigerant has been removed from the
compressor crankcase or the resultant pres-
sure will forcibly discharge compressor oil.
CAUTION
4. Remove the oil drain plug on the bottom plate of the
Extreme care must be taken to ensure that the compressor and drain oil from the compressor as
manifold common connection remains im-
mersed in oil at all times or air and moisture required.
will be drawn into the system. 5. Replace the plug securely back into the
compressor.
2. Connect the suction connection of the gauge 6. Ensure that the oil level is correct.
manifold to the compressor suction service valve 7. Evacuate the compressor.
port. 8. Open discharge and suction valves.

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Unloaders 5. Using refrigerant hoses designed for vacuum

Although the electric unloaders are non-adjustable, service, connect a vacuum pump to center
they will require some periodic maintenance. Service connection of manifold gauge set. Evacuate
kits are available for repair of the electric unloaders system to 500 microns. Close off pump valve,
solenoid and stem assemblies. isolate vacuum gauge and stop pump. Wait 5
To check the unloaders proceed as follows: minutes to verify that vacuum holds.
1. Ensure that the compressor is fully loaded. Heat the 6. When vacuum is maintained, recharge low side with
interior of the coach if necessary. R-134a to 20 to 30 psig by admitting vapor from the
2. Connect manifold gauges to compressor refrigerant cylinder. Backseat compressor service
valves and disconnect manifold gauge set.
3. Slowly frontseat the suction valve until 26 psig
shows on the suction gauge. The first unloader Pump Down an Operable Compressor for
should energize (check for magnetism at the Repair
unloader coil) increasing suction pressure by 3 to 5 To service an operable compressor, pump the
psig. refrigerant into the condenser coil and receiver as
4. Slowly open the suction valve until the suction follows:
gauge reads 32 psig. The first unloader should
1. Install manifold gauge set.
de---energize decreasing suction pressure by 3 to 5
psig to show it is operating properly. 2. Unplug the suction pressure transducer (SPT).
5. To check the second unloader, continue to frontseat 3. Frontseat the compressor suction service valve by
the suction valve until 21 psig shows on the suction turning clockwise.
gauge. The second unloader should energize 4. Start the unit and run in cooling until 10 inch/hg
(check for magnetism at the unloader coil) (25.4cm/hg) of vacuum is reached. Shut the system
increasing suction pressure by 3 to 5 psig. down.
6. Slowly open the suction valve until the suction 5. Turn main electrical disconnect to OFF position and
gauge reads 28 psig. The first unloader should lock.
de---energize decreasing suction pressure by 3 to 5 6. Frontseat the compressor discharge service valve
psig to show it is operating properly. and wait 5 minutes to verify vacuum is maintained. If
7. Open suction valve and resume normal operation. the pressure rises above vacuum, open the
compressor discharge service valve and repeat
Refrigerant Removal from an Inoperative
steps 3 and 4 until a vacuum is maintained.
Compressor
1. Turn main electrical disconnect to OFF position and 7. Service or replace components as required and
lock. leak check the compressor.
2. Attach a manifold gauge and isolate the 8. Using refrigerant hoses designed for vacuum
compressor by frontseating the suction and service, connect a vacuum pump to center
discharge valves. connection of manifold gauge set. Evacuate
3. Recover refrigerant with a refrigerant reclaimer. If system to 500 microns. Close off pump valve,
the discharge service valve port is not accessible, it isolate vacuum gauge and stop pump. Wait 5
will be necessary to recover refrigerant through the minutes to verify that vacuum holds.
suction service valve port only. 9. When vacuum is maintained, backseat compressor
4. Service or replace components as required and service valves and disconnect manifold gauge set.
leak check the compressor. 10. Reconnect the suction pressure transducer (SPT).

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Remove the Compressor d.) Check the oil level in the service replacement
compressor.
NOTE: Proceed only after the refrigerant has been
removed from the compressor.
GASKET SPRING
1. Turn the main battery switch to OFF position and
lock. COMPRESSOR
HEAD
2. Remove the bolts from the suction and discharge
service valve flanges.
3. Tag and disconnect the wiring to the high pressure capscrews
(NOT INTERCHANGEABLE
FLANGE
cutout switch, discharge transducer, suction COVER WITH CONTROL VALVE
BYPASS
transducer, unloaders and the clutch. PISTON
SCREWS)

4. Remove lavatory dump tube. PLUG

5. Remove wheelchair lift hydraulic hand pump (if

equipped).
6. Remove the four bolts holding compressor and FIGURE 30. Removing the Bypass Piston Plug
beltguard to its base.
9. Remove the high-pressure switch assembly and
7. Attach a sling or other device to the compressor and pressure transducers and reinstall on the
remove the compressor from the coach through the replacement compressor after checking the switch
right rear access door. operation.
8. Remove the unloader valve and bypass piston 10. Service replacement compressors are supplied
assembly (Figure 30), keeping the same with a suction filter sock for initial startup. Ensure
capscrews with the assembly. The plug filter sock is installed in accordance with the
arrangement removed from the replacement is instructions furnished.
installed in the returning compressor as a seal. If the
piston is stuck, it may be extracted by threading a Install the Compressor
socket head capscrew into the top of the piston. A 1. Install the compressor in the unit by performing
small Teflon seat ring at the bottom of the piston steps 1 through 5 in reverse. Use new locknuts
must be removed. when replacing the compressor. Install new
gaskets on the service valves and tighten the bolts
NOTE: a.) The service replacement compressors are uniformly.
sold without shutoff valves. Valve pads are installed in 2. Turn the main battery disconnect switch to ON.
their place. The customer should reinstall the 3. Dehydrate and evacuate compressor. Turn off the
unloader valves on the replacement compressor. valves on both lines to the pump.
4. Fully backseat (open counterclockwise) both
b.) The piston plug that is removed from the suction and discharge service valves. Refill the
replacement compressor head must be installed in system with refrigerant (See Charging the
the failed compressor if you are returning it for System.)
warranty. 5. Remove the vacuum pump.
6. Start the unit and check the refrigerant level.
c.) Do not interchange the Allen head capscrews that 7. Check the compressor oil level. (Refer to the next
mount the piston plug and unloader; they are not procedure) Add or remove oil if necessary.
interchangeable. 8. Check the compressor unloader operation.

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1 2 3 4 5 6 7 8 4

DRIVE END VIEW PUMP END VIEW

10

2 11
CURBSIDE VIEW 12
TOP VIEW
4 19 18 17 16 15 14 13

1 Suction Pressure Transducer

2 Bracket, Belt Guard
3 Weatherpack Clutch Coil Connector
4 Electric Solenoid Unloader
24 5 Discharge Valve Connection, Size 16 ORS
6 Discharge Service Valve
7 Discharge Valve Charging Port
8 O ring
9 Oil Drain Plug
10 Solenoid Unloader Electric Connectors
11 High Pressure Switch
12 Discharge Pressure Transducer
13 Capscrew
14 Lockwasher
15 Special Washer
23 16 Lock Nut
17 Key
18 Suction Valve Charging Port
ROADSIDE VIEW 19 Suction Service Valve
22 21 20 20 . Clutch Assembly
21 Oil Fill Plug
22 Oil Level Sightglass
23 . Suction Valve Connection, Size 24 ORS
24 . O ring

FIGURE 31. Compressor Components

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ELECTRONIC SENSORS Pressure Transducer Inspection

1. Start the coach.
Temperature Sensor Inspection
Passengers area temperature sensors are located 2. Set fast idle, activate cooling and wait for the system
behind the rear return air grills on roadside and to stabilize.
curbside. Ambient temperature sensor is located in the 3. Measure the suction or discharge pressures with
condenser compartment manifold gauges and the driver’s display
1. Use an accurate digital ohmmeter to check the diagnostics. If the pressure readings are within 3
resistance values shown in Table 13. PSIG, the sensor is good. If not, proceed.
2. Disconnect sensor leads from the harness. 4. Use a digital volt-ohmmeter to measure the voltage
across the transducer and compare the reading
3. Connect the ohmmeter to the sensor leads.
with the values in Table 14.
4. To define temperature, place the sensor in an ice
5. If the value is not within 2 percent replace the
bath or measure the temperature at the sensor with
transducer
an accurate digital thermometer.
5. Compare the resistance value obtained with the TABLE 14. Suction and Discharge Pressure
values in Table 13. If ohm readings are out of range Transducer (SPT and DPT) Voltage
by 2% or more, replace the sensor. Psig Voltage Psig Voltage Psig Voltage
6. If the resistance values is not within 2 percent 20” 0.369 105 1.495 220 2.622
replace the temperature sensor. 10” 0.417 110 1.544 225 2.671
TABLE 13. Temperature Sensor 0 0.466 115 1.593 230 2.720
(AT, TSC, TSD and TSR) Resistance 5 0.515 120 1.642 235 2.769
Temperature 10 0.564 125 1.691 240 2.818
Resistance In Ohms
_F _C 15 0.614 130 1.740 245 2.867
---20 ---28.9 165,300 20 0.663 135 1.789 250 2.916
---10 ---23.3 117,800 25 0.712 140 1.838 255 2.965
0 ---17.8 85,500 30 0.761 145 1.887 260 3.014
10 ---12.2 62,400 35 0.810 150 1.936 265 3.063
20 --- 6.7 46,300 40 0.858 155 1.985 270 3.112
30 --- 1.1 34,500 45 0.907 160 2.034 275 3.161
32 0 32,700 50 0.956 165 2.083 280 3.210
40 4.4 26,200 55 1.007 170 2.132 285 3.259
50 10.0 19,900 60 1.054 175 2.181 290 3.308
60 15.6 15,300 65 1.103 180 2.230 295 3.357
70 21.1 11,900 70 1.152 185 2.279 300 2.406
77 25 10,000 75 1.204 190 2.328 305 3.455
80 26.7 9,300 80 1.250 195 2.377 310 3.504
90 32.2 7,300 85 1.299 200 2.426 315 3.553
100 37.8 5,800 90 1.348 205 2.475 320 3.602
110 43.3 4,700 95 1.397 210 2.524 325 3.651
120 48.9 3,800 100 1.446 215 2.573 330 3.700

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Humidity Sensor Inspection Replacing Sensors and Transducers

The sensor is located beside the temperature sensor 1. Turn main battery disconnect switch to OFF.
behind the rear curbside return air grill. 2. Tag and disconnect the wiring from the defective
1. Use a sling psychrometer or other such device to sensor or transducer.
check the relative humidity inside the coach. 3. Remove and replace the defective sensor or
2. With the system running and power supplied to the transducer.
sensor, use a digital voltmeter to measure the
4. Connect the wiring to the replacement sensor or
voltage across the sensor and compare the reading
transducer.
to values in Table 15 for the measured relative
humidity. A reading within two percent of the values 5. Leak check the transducers.
in the table would be considered good. 6. Test the replacement sensor or transducer.
7. Remove and replace the defective sensor or
TABLE 15. Humidity Sensor (HS) Voltage
transducer.
Voltage %RH Voltage %RH Voltage 8. Connect the wiring to the replacement sensor or
%RH
transducer.
30 0.990 55 1.815 80 2.640
9. Checkout the replacement sensor or transducer.
35 1.155 60 1.980 85 2.805 (Refer to the above procedures as applicable.)
40 1.320 65 2.145 90 2.970
45 1.485 70 2.310 96 3.168
50 1.650 75 2.475

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TABLE 16. R-134a Temperature - Pressure Chart

BOLD NO. = Inches Mercury Vacuum (cm Hg Vac)
Temperature Pressure Temperature Pressure
_F _C Psig kPa Kg/cm@ Bar _F _C Psig kPa Kg/cm@ Bar
---40 ---40 14.6 49.4 37.08 0.49 30 ---1 26.1 180.0 1.84 1.80
---35 ---37 12.3 41.6 31.25 0.42 32 0 27.8 191.7 1.95 1.92
---30 ---34 9.7 32.8 24.64 0.33 34 1 29.6 204.1 2.08 2.04
---25 ---32 6.7 22.7 17.00 0.23 36 2 31.3 215.8 2.20 2.16
---20 ---29 3.5 11.9 8.89 0.12 38 3 33.2 228.9 2.33 2.29
---18 ---28 2.1 7.1 5.33 0.07 40 4 35.1 242.0 2.47 2.42
---16 ---27 0.6 2.0 1.52 0.02 45 7 40.1 276.5 2.82 2.76
---14 ---26 0.4 1.1 0.03 0.03 50 10 45.5 313.7 3.20 3.14
---12 ---24 1.2 8.3 0.08 0.08 55 13 51.2 353.0 3.60 3.53
---10 ---23 2.0 13.8 0.14 0.14 60 16 57.4 395.8 4.04 3.96
---8 ---22 2.9 20.0 0.20 0.20 65 18 64.1 441.0 4.51 4.42
---6 ---21 3.7 25.5 0.26 0.26 70 21 71.1 490.2 5.00 4.90
---4 ---20 4.6 31.7 0.32 0.32 75 24 78.7 542.6 5.53 5.43
---2 ---19 5.6 36.6 0.39 0.39 80 27 86.7 597.8 6.10 5.98
0 ---18 6.5 44.8 0.46 0.45 85 29 95.3 657.1 6.70 6.57
2 ---17 7.6 52.4 0.53 0.52 90 32 104.3 719.1 7.33 7.19
4 ---16 8.6 59.3 0.60 0.59 95 35 114.0 786.0 8.01 7.86
6 ---14 9.7 66.9 0.68 0.67 100 38 124.2 856.4 8.73 8.56
8 ---13 10.8 74.5 0.76 0.74 105 41 135.0 930.8 9.49 9.31
10 ---12 12.0 82.7 0.84 0.83 110 43 146.4 1009 10.29 10.09
12 ---11 13.2 91.0 0.93 0.91 115 46 158.4 1092 11.14 10.92
14 ---10 14.5 100.0 1.02 1.00 120 49 171.2 1180 12.04 11.80
16 ---9 15.8 108.9 1.11 1.09 125 52 184.6 1273 12.98 12.73
18 ---8 17.1 117.9 1.20 1.18 130 54 198.7 1370 13.97 13.70
20 ---7 18.5 127.6 1.30 1.28 135 57 213.6 1473 15.02 14.73
22 ---6 19.9 137.2 1.40 1.37 140 60 229.2 1580 16.11 15.80
24 ---4 21.4 147.6 1.50 1.48 145 63 245.6 1693 17.27 16.93
26 ---3 22.9 157.9 1.61 1.58 150 66 262.9 1813 18.48 18.13
28 ---2 24.5 168.9 1.72 1.69 155 68 281.1 1938 19.76 19.37

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TROUBLESHOOTING

CAUTION
Do not, under any circumstances, attempt to service the microprocessor. If a problem develops
with the microprocessor, replace it.

To access the LED display on the microprocessor, remove the cover of the main controller box. The box is located at
the rear of the battery compartment.

TABLE 17. Microprocessor Error Message Definition

ERROR STATUS OF
REMEDY
CODE LED DISPLAY
Er0 1 sec on - 1 sec off Not Applicable as system is operating normally.
Er4 4 flashes - 5 sec pause Record error code number, tag and replace the microprocessor.
Er5 5 flashes - 5 sec pause Record error code number, tag and replace the microprocessor.
Er6 6 flashes - 5 sec pause Record error code number, tag and replace the microprocessor.

DIAGNOSTICS FROM THE DRIVER’S DISPLAY P6 --- Discharge pressure

P20 --- Compressor hours high --- 999,999
WARNING P21 --- Compressor hours low --- 999,999
P22 --- System hours high --- 999,999
Do not access the diagnostics when the coach P23 --- System hours low --- 999,999
is in motion.
P30 --- Controller software revision numbers high ---
To access diagnostics mode, press the UP and 9857
DOWN arrows for 5 seconds. The display shows the
P31 --- Controller software revision numbers low --- 9857
alarm list first. At the end of the alarm list 3 bars --- --- ---
appear. Press the AUTO key for 5 seconds to cancel Press the I/O key to exit diagnostics. If no key is
inactive alarms. Inactive alarms appear as IXX. pressed in 30 seconds, diagnostics will exit
Press the UP arrow to move up to: automatically.
P5 --- Suction pressure

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TABLE 18. Driver Display Panel Alarm Message Definition

ALARM
TITLE CAUSE REMEDY CONTROLLER RESPONSE
NO.
A11 Main Left Main left Check the sensor Switches to the right probe. If both
Probe evaporator resistance or wiring. probes are bad, the controller will run
Failure temperature sensor Replace the sensor or in the full reheat, and evaporator fans
failure, or wiring is repair the wiring. (See will operate on low speed. The
defective, or “Temperature Sensor compressor will operate on six
sensor is Inspection” and Table 13.) cylinders if pressures permit.
unplugged.
A12 Main Right Main left Check the sensor Switches to the left probe. If both
Probe evaporator resistance or wiring. probes are bad, the controller runs in
Failure temperature sensor Replace the sensor or the full reheat, and the evaporator fans
failure, or wiring is repair the wiring. (See will operate on low speed. The
defective, or “Temperature Sensor compressor will operate on six
sensor is Inspection” and Table 13.) cylinders if pressures permit.
unplugged.
A14 Ambient Ambient Check the sensor Ignores ambient temperature and does
Probe temperature sensor resistance or wiring. not lock out the compressor, and does
Failure failure, or wiring is Replace the sensor or not open driver RAM air in AUTO
defective, or the repair the wiring. (See mode.
sensor is “Temperature Sensor
unplugged. Inspection” and Table 13.)
A15 Suction Suction pressure Check the transducer Unloaders are energized.
Pressure transducer failure voltage or wiring. Replace
Transducer or wiring is the sensor or repair the
Failure defective, or the wiring. (See “Transducer
sensor is Inspection” and Table 14.)
unplugged.
A16 Discharge Discharge pressure Check the transducer Unloaders are energized.
Pressure transducer failure voltage or wiring. Replace
Transducer or wiring is the sensor or repair the
Failure defective, or the wiring. (See “Transducer
sensor is Inspection” and Table 14.)
unplugged.
A17 Humidity Humidity Check the transducer If conditions allow, not including the
Transducer transducer failure voltage or wiring. Replace humidity setpoint/humidity sensor
Failure or wiring is the sensor or repair the condition, activates the humidity
defective, or the wiring. (See “Humidity control (dehumidifies). See “Humidity
sensor is Sensor Inspection” and Control.” Does not open the RAM air in
unplugged. Table 15.) AUTO. See “Ram Air Control.”
A18 Fuse Defective wiring or Repair or replace the All controller outputs are de-energized.
Blown coach power wiring or power source.
Alarm source defective. Replace the Fuse.
Controller Internal
fuse is blown.
A19 Main Left Main left Refer to “No evaporator air Ignores normal temperature control.
Evaporator evaporator fan flow” in Table 19. Runs the main evaporator fans on the
Fan overloads. highest allowable speed. The
Overload evaporator fan speeds can be reset by
the driver display.

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A21 Main right Refer to “No evaporator air Ignores the normal temperature
Main Right
evaporator fan flow” in Table 19. control. Runs the main evaporator fans
Evaporator
overloads. on the highest allowable speed. The
Fan
evaporator fan speeds can be reset by
Overload
the driver display.
A22 Condenser fan Refer to “Abnormal If the compressor is energized and the
overloads pressures” and/or first condenser fan overload opens, the
“Abnormal noise or controller will energize the second
vibrations” in Table 19. condenser fan in order to detect the
Condenser first overload condition.
Fan If, after energizing the second
Overload condenser fan, the second condenser
fan overload opens, the compressor
clutch will de-energize for the minimum
off time, since neither condenser fan is
operating.
A23 High discharge Check discharge pressure If this alarm has not been activated
pressure. switch, wiring or cause of three times in 30 minutes, de-energizes
high discharge pressure. the clutch for the minimum off time and
until the alarm is deactivated.
Energizes the main and driver
evaporator fans at medium speed.
De-energizes the rest of the system
unless heat is required.
High
If this alarm has been re-activated three
Pressure
times in 30 minutes, energizes the
Discharge
main and driver evaporator fans at
medium speed. De-energizes the rest
of the system unless heat is required.
Runs the main and driver evaporator
fans on medium speed until the alarm
is reset.
Evaporator fan speeds can be reset by
the driver display.
A24 Communic Communications Notification only No effect
ations Loss Loss
A25 Temperature has No remedy No controller response other than
exceeded ±10_F alarm.
Out of
(±5.4_C) away from
Range
setpoint for 15
minutes
A26 Low coach voltage. Check/repair the alternator De-energizes all HVAC outputs except
Coach 12 vdc or coach power supply. driver evaporator fan motor. (See
Low
battery supply Check the equalizer. “Alternator status” under “Operation”)
Voltage/
voltage dropped
Load Shed
below 12.6 vdc for
30 seconds.

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 Date March 2003 Page 16A-48

A27 Low suction Check the cause of low If an alarm has not been activated
pressure. suction pressure. (Refer to three times in 30 minutes,
“Abnormal Pressures” in De-energizes the clutch for the
Table 19.) minimum off time and until the alarm is
deactivated. Energizes the main and
driver evaporator fans at medium
speed unless heat is required.
De-energizes the rest of the system.
Low
If an alarm has been re-activated three
Pressure
times in 30 minutes, energizes the
Shutdown
main and driver evaporator fans at
medium speed. De-energizes the rest
of the system unless heat is required.
Runs the main and driver evaporator
fans at medium speed until the alarm is
reset.

Evaporator fan speeds can be reset by

the driver display.
A28 Power source Check, repair or replace All controller outputs are de-energized.
High
voltage is greater the alternator.
Voltage
than 17 vdc.
A29 Power source Repair or replace the All controller outputs are de-energized.
Low
voltage is less than wiring or alternator.
Voltage
10 vdc.
A31 Memory failure. Replace the main Modifies out-of-range values to their
EEPROM controller at the next default values.
service stop.

MOTOR COACH INDUSTRIES

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 Date March 2003 Page 16A-49

TABLE 19. General System Troubleshooting Procedures

INDICATION/TROUBLE POSSIBLE CAUSES REFERENCE SECTION
SYSTEM WILL NOT COOL
Compressor will not run V-Belt loose or defective Check
Clutch coil defective Check/Replace
Clutch malfunction Check/Replace
Compressor malfunction See Note
Electrical malfunction Coach power source defective Check/Repair
Circuit Breaker/safety device open Check/Reset
SYSTEM RUNS BUT HAS INSUFFICIENT COOLING
Compressor V-Belt loose or defective Check
Compressor valves defective See Note.
Refrigeration system Abnormal pressures “Abnormal Pressures” (below),
No or restricted evaporator air flow “No evaporator air flow” (below),
Expansion valve malfunction “Expansion valve malfunction”
Restricted refrigerant flow “Thermostatic Expansion valve”,
Low refrigerant charge “Refrigerant leak check”
Service valves partially closed Open
Safety device open Safety devices
Liquid solenoid valve stuck closed. Check
Heat Valve Open. Check power at valve.
ABNORMAL PRESSURES
High discharge pressure Refrigerant overcharge “Pumping the system down”
Noncondensable in system See Check for Non-Condensables
Condenser fan rotation incorrect Check
Condenser coil dirty Clean
Low discharge pressure Compressor valve(s) worn or broken See Note.
Low refrigerant charge Refrigerant leak check
High suction pressure Compressor valve(s) worn or broken See Note.
Low suction pressure Suction service valve partially closed Open
Filter-drier inlet valve partially closed Check/ Open
Filter-drier partially plugged “Filter-drier”
Low refrigerant charge “Refrigerant leak check”
Expansion valve malfunction “Exp. valve malfunction” below
Restricted air flow “No evaporator flow” below
Suction and discharge pressures Compressor valve defective See Note.
tend to equalize when the sys-
tem is operating

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 Date March 2003 Page 16A-50

ABNORMAL NOISE OR VIBRATIONS

Compressor Loose mounting hardware Check/Tighten
Worn bearings See Note.
Worn or broken valves See Note.
Liquid slugging “Exp. valve malfunction” below
Insufficient oil “Model 05G Comp. maintenance”
Clutch loose, rubbing or is defective Check
V-belt cracked, worn or loose Check/Adjust
Dirt or debris on fan blades Clean
Condenser or evaporator fans Loose mounting hardware Check/Tighten
Defective bearings Replace
Blade interference Check
Blade missing or broken Check/Replace

CONTROL SYSTEM MALFUNCTION

Will not control Sensor or transducer defective Appropriate maintenance
procedure
Relay(s) defective Check
Microprocessor controller malfunction Check
Check power to 12V microprocessor controller See MCI HVAC Schematic.
form MCI 12V module#3 in MCI module box.
NO EVAPORATOR AIR FLOW OR RESTRICTED AIR FLOW
Air flow through coil Coil frosted over Defrost coil
blocked Dirty coil Clean
Dirty filter Clean/Replace
No or partial evaporator air Motor running in reverse Check
flow Motor(s) defective Repair/Replace
Motor brushes defective Replace
Evaporator fan loose or defective Repair/Replace
Fan damaged Repair/Replace
Return air filter dirty Clean/Replace
Icing of coil Clean/Defrost
Fan relay(s) defective Check/Replace
Safety device open “Safety Devices”
Check
Engine runs but A/C fans Bad equalizer lowers 12V supply voltage to the Replace equalizer
will not start or they start in main controller, causing low voltage alarm.
15 to 30 minutes
EXPANSION VALVE MALFUNCTION
Low suction pressure with Low refrigerant charge “Refrigerant leak check”
high superheat Wax, oil or dirt plugging the valve orifice Check
Ice formation at the valve seat “Evacuation and Dehydration”
Power assembly failure Replace
Loss of bulb charge Replace
Broken capillary “Thermostatic exp. valve”
Low superheat and liquid Superheat setting too low “Thermostatic exp. valve”
slugging in the compressor Ice or other foreign material holding valve open “Evacuation and Dehydration“

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NO OR INSUFFICIENT HEATING
Insufficient heating Dirty or plugged heater core Clean
Coolant solenoid valve(s) malfunctioning or Check/Replace
plugged Check
Low coolant level Check/Replace
Coolant bypass valve open or malfunctioning Clean
Strainer(s) plugged Open
Hand valve(s) closed Repair/Replace
Water pumps defective Repair/Replace
Auxiliary Heater malfunctioning.
No Heating Coolant solenoid valve(s) malfunctioning or Check/Replace
plugged Replace
Controller malfunction Repair/Replace
Pump(s)
p( ) malfunctioning
g
Safety device open “Safety devices”

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SPECIFICATIONS
REFRIGERATION CHARGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . R-134A: 17.5 LB (7.94 KG)

CONDENSER
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Carrier Transicold

EVAPORATOR-- DRIVER’S
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Carrier Transicold
Superheat Setting (Nonadjustable) 5 to 15_F (2.5 to 8_C)

EVAPORATOR-- PASSENGER
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Carrier Transicold
Superheat Setting (Nonadjustable): 15 to 25_F (6.7 to 14_C)

EVAPORATOR-- PARCEL RACK

Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Carrier Transicold
Superheat Setting (Nonadjustable) 5 to 15_F (2.5 to 8_C)

COMPRESSOR
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Carrier Transicold
Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 VDC
Model: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 05G
No. of Cylinder: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Weight (Dry): . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145 lb (66 kg) including clutch

OIL CHARGE:
New Compressor: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.8 pints (3.2 liters)
Replacement Compressor: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5 pints (2.6 liters)

OIL LEVEL:
Level in sight glass between Min-Max marks on compressor crankcase (curbside)

APPROVED COMPRESSOR OILS - R-134A:

Castrol: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Icematic SW68C
Mobil: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . EAL Arctic 68
ICI: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Emkarate RL68

HIGH PRESSURE SWITCH

Opens at: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 385 ±10 psig (2.6 mPa ±69 kPa)
Closes at: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285 ±10 psig (2.0 mPa ± 69 kPa)

FILTER DRYER
Manufacturer: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Alco

DRIVER’S FAN CONTROLLER

Manufacturer: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Carrier
Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 VDC

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ELECTRICAL SPECIFICATIONS - WOUND FIELD MOTORS

A. PASSENGER EVAPORATOR/HEATER BLOWER (FAN) MOTOR

Bearing Lubrication: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Factory Lubricated (additional grease not required)

FULL LOAD AMPS (FLA.)

High Speed: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Medium Speed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Low Speed: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

B. DRIVER EVAPORATOR/HEATER BLOWER (FAN) MOTOR

Bearing Lubrication: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Factory Lubricated (additional grease not required)
Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 VDC
Full Load Amps (FLA) each: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Total blowers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

C. CONDENSER FAN MOTOR

Bearing Lubrication: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Shell Dolium R
Horsepower: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.8 hp (1.072 kw)
Voltage: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 vdc

FULL LOAD AMPS (FLA)

High Speed: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Low Speed: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

D. PARCEL RACK EVAPORATOR

Bearing Lubrication: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Factory Lubricated (additional grease not required)
Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 VDC
Full Load Amps (FLA) each: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

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ELECTRICAL SPECIFICATIONS

MAIN CONTROLLER, INPUT SENSORS AND TRANSDUCERS

MAIN CONTROLLER
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Carrier Transicold
Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12/24 VDC

DRIVER’S HVAC DISPLAY

Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Carrier Transicold
Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12VDC

HUMIDITY SENSOR
Power Requirements: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 vdc ± 5% (approx. 2 mA, max. 5 mA)
Operating Range: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 to 140 _F (0 to 60_C)
Measurement Range: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . >30 to <90% Relative Humidity
Output Range: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 to 3.3 vdc for 0 to 100% Relative
Output Voltage: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vdc = 0.033 x RH (See Table 15 for calculations.)

SUCTION AND DISCHARGE PRESSURE TRANSDUCER

Supply Voltage: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5 to 5.5 vdc (5 vdc nominal)
Supply current: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 mA maximum
Output Range: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8K ohms minimum
Input Range: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ---6.7 to 450 psig ( ---46.2 kPa to 3.1 mPa)
Output Current: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -1.5 mA minimum to 1.5 mA maximum
Output Voltage: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 to 5 vdc (See Table 14 for calculations.)

TEMPERATURE SENSORS
Input Range: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ---52.6 to 158_F ( ---47 to 70_C)
Output: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . NTC 10K ohms at 77_F (25_C)
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (See Table 13 for calculations.)

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SERVICE TOOLS
SOME OF THE TOOLS LISTED IN THIS SECTION ARE DESIGNED TO MEET
SPECIFIC SERVICE THE NEEDS. THESE TOOLS ARE AVAILABLE THROUGH
MCI SERVICE PARTS OR, WHERE PRACTICAL, MAY BE MANUFACTURED BY
THE OPERATOR.

Refrigerant recovery system Gauge manifold with valves (16C-- 2-- 98)
Vacuum pump -- minimum 5 CFM Refrigerant charging hoses (16C-- 2-- 95)
Suction pressure gauge 0-- 150 PSIG (16C-- 2-- 97) Remote temperature sensing probe (16C-- 2-- 99)
Discharge pressure gauge 0-- 500 PSIG Electronic refrigerant leak detector
(16C-- 2-- 96) Suction filter sock (16L-- 2-- 105)

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SECTION 16B
AUXILIARY HEATER
(SERIES 60 / DIESEL FUEL)
CONTENTS OF THIS SECTION

SUBJECT PAGE
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16B-3
Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16B-4
Proheat Major Assemblies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16B-6
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16B-11
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16B-13
Troubleshooting & Diagnostics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16B-17
Function Error Diagnostics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16B-19
Component Fault Diagnostics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16B-24
Mechanical Component Fault Diagnostics . . . . . . . . . . . . . . . . . . . . . . . . . 16B-35
Service Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16B-41
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16B-43

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Proheat X45 Auxiliary Heater Installation

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GENERAL DESCRIPTION momentary switch is pushed to stop the preheat cycle,

or the 90 minute “time out” expires, or (supplemental
The Proheat X45 auxiliary heater provides operation) the engine stops.
supplement engine heating and coach heating. A The Proheat is mounted on a bracket attached to the
preheat function helps engine starting in cold weather. coach frame at the left rear corner of the engine
In pre-heat (switch enabled) or supplemental (engine compartment. Access is through the roadside rear
enabled) operation, the auxiliary heater heats the engine access door and the left rear radiator access
coolant until the temperature reaches 185_ F (85_ C), door (Figure 1).
then cycles off. When the coolant temperature falls The electrical diagnostic LEDs on the PCM (Proheat
below 150_ F (65_ C), the heater cycles on. This cycle Control Module) are visible from the rear left-hand corner
continues until (pre-heat operation) the AUX/HEAT of the engine compartment.

LEFT REAR ENGINE BAY FROM LEFT REAR RADIATOR ACCESS DOOR

FIGURE 1 -- Proheat X45 Auxiliary Heater Location Views

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COMPONENTS
Auxiliary heater components are shown in Figure 2.
The purpose and function of each component is briefly
described.

10 13 Roadside (LH) End View

12

11 8

9 6

Fuse Holder & Fuse

3
14
6
2

1
4
5
Curbside (RH) End View

FIGURE 2 -- Proheat X45 Auxiliary Heater Components

1. Fuel Pump 2. Fuel Regulator

A gear pump driven from the same motor as the Reduces fuel to atmospheric pressure and provides
compressor pulls fuel from the tank. The fuel is filtered at siphoning action from the nozzle, drawing fuel from the
the fuel pump inlet. The gear pump will develop a regulator.
maximum pressure of 10 PSI on the outlet side of the
pump.

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3. Air Compressor the spark jumps the gap between the electrode and the
A diaphragm type compressor supplies air to the fuel combustion tube, igniting the air/fuel mixture. Spark
nozzle. duration is 60 seconds.

4. Ignition Coil 12. Coolant Temperature Sensor

An automotive type ignition coil supplies high voltage Measures coolant temperature at the heat exchanger
spark to the ignition electrode. outlet port.

5. Coolant Pump 13. Overheat Breaker Sensor

An impeller type non-priming pump circulates the Protects the heater from damage resulting from
engine coolant. The pump must be full of coolant and all operating without coolant. The overheat breaker
air purged in order to operate. DO NOT start the monitors the surface temperature of the heat exchanger
PROHEAT if no coolant is in the pump. casting. When the temperature reaches 286_ F (141_ C)
the breaker “trips out”, shutting power off to the air
6. Proheat Control Module compressor and extinguishing the flame. The breaker is
Has a microprocessor to monitor operating reset by pushing down on the red button located under
conditions and govern Module (PCM) outputs to the the rubber cap.
motors and sensors. The diagnostic display on the front
of the PCM has LEDs to indicate function or component 14. Flame Sensor
problems for troubleshooting. Photo-electrically measures flame intensity. The
Flame Sensor tells the PCM that the air/fuel mixture is
NOTE: The Proheat PCM uses “ground-side” burning properly.
switching for the blower, compressor, coolant
pump and ignition coil. The positive wire to the 15. Aux/Heat Switch
motors and ignition coil will show voltage even The momentary-type ON/OFF rocker switch is
when the heater is switched “OFF.” mounted in the left hand Control Console.

7. Nozzle
An air/fuel aspirating type spray nozzle is located
inside the housing to regulate the air/fuel ratio. The
compressed air flows through the nozzle at high speed
creating a venturi effect, which siphons fuel from the
regulator, mixing it with the air. This mixture is sprayed
out of the nozzle into the combustion chamber to ignite
and heat the coolant.

8. Blower
Uses an impeller-type fan to supply approximately
90% of the combustion air at low pressure. It also cools
and purges the combustion chamber during the 3
minute shut-down sequence.

9. Inspection Port FIGURE 3 -- Auxiliary Heater Control Switch

Allows visual inspection of the combustion process Pushing the switch enables the auxiliary heater
and is useful for troubleshooting and servicing the PREHEAT mode. The power-on LED on the PCM lights
heater. and a system diagnostic starts. If the red power-on LED
flashes continuously, the heater diagnostic detects a
10. Heat Exchanger
system error.
A two-part cast aluminum housing where coolant
temperature is increased approximately 10_ to 15_ F (6_ Pushing the switch when the auxiliary heater is
to 8_ C) as it passes through the heat exchanger. powered disables the auxiliary heater PREHEAT mode.
If the PREHEAT mode is in mid-cycle, the system goes
11. Ignition Electrode into a three minute purge cycle and then disables. An
The electrode is located near the nozzle just outside internally programmed 90 minute “time out”
the air/fuel mixture path. During the ignition sequence automatically switches off the Proheat.

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PROHEAT MAJOR ASSEMBLIES auxiliary heater installation in the engine compartment.

If parts need to be replaced for maintenance, please
Exploded views are shown of the major Proheat refer to the MCI Parts Book. Look in Section 16 ---
Assemblies: Blower, Heat Exchanger, Air Heating & Air Conditioning, Section D ---Auxiliary Heater
Compressor/Fuel Pump, Electrical System. Key for the MCI Part Numbers and quantity required. The
numbers match the accompanying itemized MCI Parts Book is considered the major reference when
components description. A diagram also shows the part numbers are required.

1. Air & Fuel Elbow -- 3/16” x 1/8”NPT 11. Fuel Nozzle (30609--32), with O-Ring
2. Flame Sensor 12. Nozzle O-Ring
3. 10--24NC x 5/8” Hex Head Screw 13. Fan End Casting --
4. 1/4NC x 5/8” Hex Flange Screw with Screen & Sight Glass
5. Igniter Seat Gasket 14. Fuel Hose Clamp
6. Igniter & Gasket 15. Fuel Regulator
7. Ignition Lead with Boot 16. Air & Fuel Hose -- 3/16” I.D.
8. Sight Glass Kit 17. Blower Inlet Screen Kit
9. 24 Volt Blower 18. Green Air Spring Clamp
10. Blower Gasket 19. Fan Blade with Glue

FIGURE 4 -- Proheat Blower Assembly

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9 1
11
10

2
3 4
12

6
13
7
8

1. Heat Exchanger with Elbows 8. Ignition Lead with Boot

2. Combustion Tube 9. 3/4” Hose x 1/2NPT Elbow
3. 10--24NC x 1/2” Socket Head Screw 10. 1/4NC Nylon Jam Nut
4. # 10 Lockwasher 11. 3/8” ID Cushioned Clamp
5. 1/4NC x 5/8” Hex Flange Screw 12. Rubber Mount Kit
6. “J” Bracket 13. # 32 Gear Clamp
7. Ignition Coil

FIGURE 5 -- Proheat Heat Exchanger Assembly

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1. 24 Volt Compressor 13. Air Filter

2. Coupling 14. Compressor/Fuel Pump Bracket
3. Gear--Type Fuel Pump 15. # 36 Gear Clamp
4. # 10 Stainless Steel Lockwasher 16. 1/4NC x 1/2” Socket Head Screw
5. # 10 -- 24 x 2 Stainless Steel Screw 17. 1/4” Lockwasher
6. Filter Cap Fitting 18. 3/4” I.D. Coolant Hose
7. Elbow 19. # 10 Silicon Clamp
8. Fuel Filter O-Ring 20. 24 Volt Coolant Pump
9. Fuel Filter 21. “J” Bracket
10. Relief Valve Kit 22. 1/4NC x 5/8” Hex Flange Screw
11. 1/4--20NC Screw 23. # 32 Gear Clamp
12. Sealing Washer 24. # 4 SAE Fitting

FIGURE 6 -- Proheat Compressor/Fuel Pump Assembly

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1. Proheat Control Module 9. Temperature Sensor O-Ring

2. Main Internal Harness 10. 10--24NC x 5/8” Hex Head Screw
3. Fuse Holder Kit 11. Wire Harness Clip
4. 15 Amp Fuse 12. Overheat Sensor -- with O-Ring
5. 1/4NC x 5/8” Hex Flange Screw 13. Overheat O-Ring
6. Controller Spacer 14. Switch Harness
7. Controller Mount Grommet 15. Power Harness
8. Temperature Sensor with O-Ring 16. Connector Cover

FIGURE 7 -- Proheat Electrical System Assembly

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COACH REAR FRAME ASSEMBLY

3
ENGINE
AREA
1. Proheat X45 Auxiliary heater
2. Vertical Support Plate
3. Proheat Support Bracket 4
4. Exhaust Pipe 7
5. Muffler Clamp
6. Exhaust Pipe Rubber Plate
7. Exhaust Pipe Support Bracket

6
Roadside Curbside

Rear View
(From Rear Engine Service Door - Left Hand Corner)

FIGURE 8 -- Proheat Auxiliary Heater Installation

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OPERATION The electrical diagnostic LEDs on the PCM (Proheat

Control Module) are visible from the rear left hand corner
The auxiliary heater works in conjunction with the of the engine compartment.
engine heating system. The heater operates in two
modes: PREHEAT, which is controlled by the AUX/HEAT
momentary rocker switch and SUPPLEMENTAL, which
is fully automatic and enabled when the engine starts.
The SUPPLEMENTAL mode automatically overrides
the PREHEAT mode.

PREHEAT OPERATION
Pushing the momentary ON/OFF rocker switch
powers up the auxiliary heater and pre-heats the engine
coolant before starting the engine. The auxiliary heater
heats the engine coolant to a temperature of 185_ F (85_
C) and cycles off. When the coolant temperature falls
below 150_ F (65_ C), the heater cycles on.
This preheat cycle continues until the heater is
powered down by pushing the momentary switch or if
the internally programmed 90 minute “Time Out”
operation period finishes and the Proheat automatically
switches off.
FIGURE 9 -- Proheat Control Module LED Display
NOTE: Pushing the momentary ON/OFF switch
during a heating cycle puts the Proheat into a a
three minute purge cycle, then the Proheat stops.

SUPPLEMENTAL OPERATION
The Supplemental mode is a fully automatic
on-demand system controlled by a built-in sensor which
monitors engine coolant temperature at the Proheat.
Starting the engine enables the Supplemental Heat
mode. Stopping the engine disables the Supplemental
Heating mode.
The Proheat runs at full output until the coolant
temperature reaches 185_ F (85_ C). The Proheat then
goes on standby, deactivating the coolant pump until
the engine coolant temperature drops to 150_ F (65_ C) Not Used
at the heater outlet. When the built in sensor detects the
lower temperature, the heating cycle repeats until the FIGURE 10 -- Function / Component Diagnostics
coolant temperature again reaches 185_ F (85_ C).
The number of flashes corresponds to the numbered
FUNCTION & COMPONENT DIAGNOSTICS diagnostic code LEDs; 5 flashes indicates a VOLTAGE
The microprocessor in the PCM continually monitors ERROR. A pause follows the numbered flashes and then
all the PROHEAT systems. If the internal diagnostics the series of LED flashes repeats.
detect a problem, a diagnostic code, shown as a series If a diagnostic code flashes, refer to the
of LED flashes, is displayed on the PCM function display. troubleshooting section to assist in problem diagnosis.

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OPERATING PROBLEMS Low Heat Output

These problems generally occur on first start-up of a The heater appears to be functioning properly but
new auxiliary heater system. These are mostly there is low heat output. This usually indicates a coolant
mechanical problems that may relate to a minor flow restriction.
electrical or system problem. Refer to the main Refer to Function Error Diagnostics --- 3. Coolant Flow.
Troubleshooting/Diagnostics section if following the Engine Temperature Gauge Reads Low
logic-solution to these problems discloses a more
The engine temperature sensor may be blocked from
advanced problem.
the direct path of coolant flow from the heater. In this
situation, the gauge may read significantly lower than
Smoking Exhaust -- Smelly Exhaust Fumes actual coolant temperature.
These symptoms usually indicate an extremely rich
Check:
air/fuel mixture.
The engine temperature sensor.
Check:
Backfiring
1. Is the PROHEAT Connected to the correct voltage?
Backfiring occurs when there is air in the fuel supply
Refer to Function Error Diagnostics --- 5. Voltage.
lines.
2. Is the blower working? Is the air inlet restricted?
Check:
3. Is the compressor working? Refer to Component 1. Fuel level in tank --- is the pick-up submerged?
Fault Diagnostics--- 9. Compressor.
2. Air leaks --- are all the fuel line clamps tight?
4. Is the exhaust restricted? 3. Severely restricted combustion air blockage at the
5. Is it a new heater? New heaters may smoke for a blower inlet, in the combustion chamber, or in the
short period as oil is burned off the exhaust pipe. exhaust system.

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MAINTENANCE
WARNING
WEEKLY MAINTENANCE
Run the heater once a week to keep new fuel in the Thoroughly wipe up all spilled fuel. Dispose
fuel pump and lines and to check the basic function of of fuel-soaked rags in a safe container. Do
the Proheat system. not smoke or use flame or spark-producing
equipment or tools around a fuel system.
ANNUAL MAINTENANCE
Check the system yearly before operation. 9. Disconnect the switch and power harnesses from
Preliminary level maintenance procedures are listed that the plug-in connectors on the side of the PCM. Also
will help keep the Proheat auxiliary heater working disconnect the ground (---) lead from the Proheat
efficiently. chassis ground boss.
Contact your Authorized PROHEAT Dealer who has 10. Loosen the clamp fastening the Proheat exhaust
the required specialized equipment for major overhaul flex tube to the exhaust pipe.
maintenance.
NOTE: The lower exhaust pipe bracket may
PROHEAT UNIT REMOVAL require loosening to separate the exhaust flex
tube from the exhaust pipe.
Some Maintenance, Troubleshooting & Diagnostics
procedures may be easier to do if the Proheat unit is 11. Loosen the bolts and nuts fastening the Proheat
removed from the engine bay. Follow these steps to chassis to the mounting bracket.
remove and install the Proheat unit.
12. Make sure all lines, connectors and any
1. Turn main battery disconnect switch OFF. mechanical attachments are disconnected and
2. Push the “AUX/HEAT” ON/OFF momentary Switch detached from the Proheat chassis.
to power down the auxiliary heater if the “ON” LED 13. Tie back to prevent interference with the Proheat
in the PCM is lit. unit when lifting from the mounting bracket.
3. On the engine compartment rear junction box, 14. Lift the Proheat unit out through the rear engine
move the Starter Control FRONT/REAR switch to bay service door area.
“REAR” and the Engine enable ON/OFF switch to
“OFF”. PROHEAT UNIT INSTALLATION
1. Install and mount the Proheat unit in reverse order.
NOTE: Some components can be reached
2. After installing, check all mechanical and electrical
through the roadside rear radiator access door
connections.
and the rear engine service doors.
After disconnecting coolant lines, switch and 3. Turn on the Proheat and operate through a
power harnesses, the fuel line and the exhaust complete cycle to make sure the systems are
working properly. Observe the diagnostics LEDs on
pipe, lift the Proheat unit from the engine bay.
the PCM. Refer to the “OPERATION” and
“FUNCTION & COMPONENT DIAGNOSTICS”
4. Have a container and rags handy to catch and wipe
headings which explain the system functions.
up any residual coolant that may come from the
coolant pipes. Clean Heater Installation Area
5. Unfasten the clamps securing the coolant inlet and Blow out around the installation area with
outlet hose connectors to the Proheat unit. compressed air. Clean any accumulated debris or dust
6. Slide the hose connectors away from the Proheat from the components. Make sure the opening around
and plug to prevent coolant from leaking into the the exhaust pipe is clear. Visually inspect all the
work area. components for wear or damage.
7. Disconnect the fuel line from the fuel pump. Plug the Heat Exchanger
fuel line and the fuel pump inlet. To maintain efficient heat output, clean accumulated
8. Wipe up any leaked fuel with rags. combustion deposits from the heat exchanger fins.

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Exhaust System
Heat Exchanger Housing Check the exhaust system carefully. Check the pipe
for dents, restrictions or severely corroded areas.
Combustion Tube Replace the exhaust pipe and clamps if necessary.
Ensure the exhaust pipe clamp is tight.

Proheat X45
Auxiliary Heater

Heat Exchanger Fins

Capscrews & Lockwashers Proheat X45

Mounting Bracket
ROTRON
FIGURE 11 -- Heat Exchanger Fins Access Pump Exhaust Pipe
Exhaust Pipe
1. Turn the main battery disconnect switch to OFF. Support Bracket
2. Push the “AUX/HEAT” ON/OFF momentary Switch
Exhaust Pipe
to power down the auxiliary heater if the “ON” LED Rubber Plate
in the PCM is lit.
3. Remove ignition lead from ignition electrode.
4. Remove blower connector. Muffler Clamp
5. Remove the 4 capscrews securing the fan end
assembly. FIGURE 12 -- Exhaust System
6. Remove the fan end assembly and combustion Clean Air Intake
tube to access the inside of the heat exchanger. Check the combustion air inlet screen for restrictions.
Use a wire brush to loosen deposits and Clean as required.
compressed air to blow out of the heat exchanger
housing.
7. Also blow off the combustion tube. Wipe the tube Air Intake Screen
and exchanger housing with a shop rag.
8. Reverse this procedure to assemble and install the
components.

FIGURE 13 -- Air Intake Cleaning

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Fuel System
Check the fuel system for damaged fuel lines or
leakage. Make sure the clamps on the fuel lines are
secure. Check the fuel filter and replace if dirty. Check
the fuel pump relief valve for sticking or restriction.
Replace with a Relief Valve Kit.
Check the air compressor air filter and replace if dirty.
Relief Valve Location
Compressor (rear of fuel pump)
Compressor Assembly
Air Filter

Fuel Pump
Assembly

Relief
Valve Kit
(Located at back FIGURE 15 -- Relief Valve Location
of fuel pump)

Fuel Line &

Clamp
Fuel filter Housing (at fuel pump)

Fuel Line & Clamp

(from tank)

FIGURE 14 -- Fuel Lines & Clamps

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Electrical System Vehicle Batteries

The Proheat is a 24 volt system, switched through the Check the condition of the batteries and the power
ground (---) side of the battery. This provides constant 24 connections. The heater will not function properly with
volt power to the PCM even if the main battery weak batteries or corroded connections. Load test each
disconnect switch is “OFF”. battery and replace if not up to test specifications. Clean
A 15 amp fuse at the main battery disconnect switch terminals to remove corrosion.
and at the PCM protects the Proheat electrical system.
Operation Test
Run the system until the heater cycles “OFF” and then
CAUTION “ON” again. Observe whether any PCM LEDs flash in
sequence code, indicating a system or component
Do not replace blown fuses with a higher error. Refer to the Troubleshooting/Diagnostics Section
amp capacity. Only use 15 amp rated fuses. to identify and correct.
Electrical System Schematic
Check the wire harnesses and connectors visually for Refer to the Proheat Electrical System Schematic, in
damage. Replace if required. Section 7 - Electrical.

CAUTION
Disconnect the Proheat power cable at the
PCM before welding the coach frame or
components. Do this to prevent damage to
the Proheat electrical system.
See the “INTRODUCTION” Section for weld-
ing CAUTIONS.

7
1. Main Internal harness & Connector
2. Ignition Lead 3
3. Switch Harness & Connector
4. Power Harness
5. Ignition Coil
6. Proheat Control Module (PCM)
7. Fuse Holder & Fuse 1
(located at end of PCM-- Roadside)

5
6 4

FIGURE 16 -- Main Wire Harnesses, Leads & Connectors

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TROUBLESHOOTING Component Faults:

This section covers the individual heater
TROUBLESHOOTING & DIAGNOSTICS components. A flashing LED indicates an electrical
The Troubleshooting & Diagnostics Guide is divided problem, NOT a mechanical failure. Component
into three sub-sections. One covers the Function Errors problems can also cause related Function diagnostic
diagnostic LEDs, the second covers the Component codes to flash.
Faults diagnostic LEDs on the control module and the
third covers Mechanical Components.
Each sub-section explains the LED code, symptoms
that may occur, logic-solution checks and applicable
diagnostic tests and procedures.
Refer to the Proheat Electrical System Schematic in
Section 7 - Electrical as required when performing
diagnostics and troubleshooting.
A Special Tools section shows and explains various
test equipment and tools for servicing the Proheat X45
auxiliary heater.
Function Errors:
Errors displayed on the PCM diagnostic panel cause
the heater to shut down. These diagnostic codes are
usually caused by a system problem. Not Used
Two or more diagnostic codes can flash at the same
time. A function diagnostic code may flash in
FIGURE 17 -- Function & Component Diagnostics
conjunction with a flashing component diagnostic code.

FIGURE 18 -- Function & Component Diagnostic LEDs

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This PCM LED display layout

table identifies the code descrip-
tions and number of flashes for
each display.
NOTE: The X45 fuel pump is
a gear pump driven directly
by the compressor motor
and is not monitored electri-
cally. If this component diag-
nostic code flashes, there is
a fault in the main wire har-
ness connector or in the
PCM.

Fuel pump mechanical prob-

lems are indicated by either
a START (1) or a FLAME OUT
(2) Diagnostic Code.

Mechanical Components: NOTE: Always let the heater run through two
This section includes the electrode gap, fuse, nozzle cycles when troubleshooting. The heater will
and fuel regulator. attempt one restart after any function or
component diagnostic code. The heater will not
start if the coolant temperature is above 150_ F
(65_ C).

“ON” LED FLASHING

A continuously flashing “ON” LED indicates a
problem in the PCM.

Check: Heater PCM function

1. Switch the heater START/OFF/STOP switch in
the dash to “OFF.” Reset the PCM by removing
the power connection for 10 seconds and then
reconnecting. If the “ON” light continues to
flash, replace the PCM.

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FUNCTION ERROR DIAGNOSTICS

FUNCTION DIAGNOSTICS

1. “START” LED FLASHING

A START diagnostic code indicates that the flame
sensor did not see a flame during the 60 second ignition
period.
If the START diagnostic code is displayed, switch the
heater off (STOP) and then on (START) to restart. Ob-
serve the heater operation through the inspection win-
dow.

Symptom: Flame Visible NOTE: A spark should be visible across the gap
The heater shuts down after the 60 second ignition between the ignition electrode and the
period. combustion tube.

Check: Flame Sensor Symptom: Heater Is Backfiring

Refer to Component Fault Diagnostics, Backfiring is usually caused by a severe restriction
Figure 22 ---Flame Sensor Diagnostics Flow Chart. of combustion air or air in the fuel line.
1. Inspect for an open circuit in the wiring.
Check: Inlet Air Flow
2. Inspect the lens for cleanliness.
1. Is a blower error displayed?
Check: Fuel System 2. The blower operation --- is it turning? --- is it turning
NOTE: Apply the following diagnostic references slowly?
to all of the Fuel system Symptoms & Checks. 3. For restrictions at the fan inlet port and in the
Refer to Component Fault Diagnostics --- 8. Fuel exhaust system.
Pump, 9. Compressor, 12. Blower, Fuel System 4. For carbon build-up in the combustion chamber.
Diagnostics --- Fuel Regulator, Nozzle. Check: Fuel System
1. Is there a restriction in the fuel system? 1. Is fuel level low?
2. Is the nozzle plugged? 2. Air leaking into fuel system?
3. Is the fuel pump operating?
Symptom: No visible flame
4. For a defective pressure regulator. No spark. The heater shuts down after the 60
5. Is the compressor functioning? second ignition period.
6. What type of fuel is being used?
Check: Ignition System
Symptom: No Flame Visible Refer to Component Fault Diagnostics --- 7. Temp
The spark continues for the 60 second ignition Sensor, 10. Ignition Coil.
period. The heater shuts down after the 60 second 1. Check for a poor electrical connection between the
ignition period. ignition coil and the high tension lead.
2. Check for a poor electrical connection between the
Check: Fuel System
electrode and the high tension lead.
1. Is there a restriction in the fuel system?
3. Inspect the electrode gap. Check for carbon
2. Is the nozzle plugged? bridging from the ignition electrode to the
3. Is the fuel pump operating? combustion tube.
4. For a defective pressure regulator. 4. Inspect the primary electrical connections to
5. Is the compressor functioning? ignition coil and coil function.

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5. Is the heater chassis ground wire attached. The

ground is connected to the boss located near the
fuel pump.

2 FLAME OUT
A FLAME OUT diagnostic code occurs when the
heater starts successfully but is unable to maintain a
steady flame.

Re-Start Attempt flame sensor fails to see a flame during Full Output, then
the FLAME OUT diagnostic code displays.
If the flame sensor does not see a flame during
ignition, the ignition electrode is switched on Check: Fuel System
immediately. If the flame is not reignited within 10 Refer to Component Fault Diagnostics --- 8. Fuel
seconds, the heater shuts down and the FLAME OUT Pump, 9. Compressor, 12. Blower, Fuel System
diagnostic code displays. The heater goes into a Diagnostics --- Fuel Regulator, Nozzle.
stand-by mode and attempts to restart in 3 minutes, 1. Is there a restriction in the fuel system?
depending on the coolant temperature. 2. Is the nozzle plugged?
A START diagnostic code displays on the function 3. Is the fuel pump operating?
control panel if the flame fails to reignite on the second 4. For a defective pressure regulator.
attempt. If the flame sensor “sees” enough of a flame 5. Is the compressor functioning?
during ignition, it enters into the Full Output mode. If the 6. What type of fuel is being used?

3. COOLANT FLOW
A COOLANT FLOW diagnostic code displays when
the coolant temperature reaches 185_ F (85_ C) in
less than one minute after ignition. This indicates that
the coolant flow is severely restricted or blocked. This
diagnostic helps detect coolant flow problems that
can lower PROHEAT efficiency and performance.

Check: Coolant Flow 3. Coolant Lines, for restrictions and blockages. Are
Refer to Component Fault Diagnostics --- 11. Coolant clamps tight?
Pump. 4. Shut-off Valves: Ensure that shut-off valves are open
1. Coolant Flow Direction--- The PROHEAT coolant and functioning properly.
pump must be pumping the coolant in the same 5. Fittings: Fittings must be at least 1/2” NPT or larger
direction as the engine coolant pump. and less than 90 degrees.
2. Check for air in the system. 6. Coolant Pump: Does the pump function properly?

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7. Coolant System Capacity: At least 3 gallons (11 NOTE: If the coolant system is contaminated with
liters) of coolant are required. If less, the coolant magnetic material, the pump impeller may seize.
may reach 185_ F (85_ C) in under one minute
causing a COOLANT FLOW diagnostic code.

4. OVERHEAT
An OVERHEAT diagnostic code displays when the
overheat breaker trips, shutting the heater down. This
occurs if the heater has been started with little or no
coolant in the heat exchanger.

Check: Coolant Flow

1. Is there coolant in the system?
2. Determine if there is a blockage or air in the
plumbing.
The compressor motor is wired in series with the
overheat breaker. The breaker contains a normally Overheat Breaker Reset
closed thermo switch. When the thermostat reaches the
preset temperature of 286_ F (141_ C), the contacts
open shutting the compressor and fuel pump OFF,
shutting the heater down. It cannot be restarted until the
breaker is manually reset.

CAUTION FIGURE 19 -- Overheat Breaker Sensor Reset

Do not reset the overheat breaker until the To reset the breaker, remove the rubber cap on top of
cause of the overheat is eliminated. the overheat breaker and press the red reset button. If
the breaker will not reset, allow the heater to cool then try
resetting the breaker again.
Polarity
Red Reset Button Plunger Not Important
Test Procedure:
Spring Connect a multimeter (adjusted to measure resist-
ance) to the overheat breaker connector. The sensor
should be normally closed. If the sensor has tripped
the circuit should be open.

FIGURE 20 -- Overheat Sensor Test

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5. VOLTAGE
A VOLTAGE diagnostic code indicates that the supply
voltage to the heater is out of the normal operating
range. The Proheat auxiliary heater is powered from the
24 Volt side of the coach electrical system.

Check: Vehicle Voltage To reset the PCM, push the left hand console
Heater voltage must be within the specified range. AUX/HEAT switch to power down the auxiliary heater
The Proheat is a 24 volt system with a voltage range of and then push to power up the heater. If the problem
20.0 to 30.0 Volts continues, load test the batteries to confirm their
Refer to the heading: “HEATER VOLTAGE condition. Test each battery independently.
MEASUREMENT” for the procedure to measure heater
voltage.
Current:
NOTE: Bad connections may show good voltage
Checking current draw is done at the power harness
under no load conditions but not under full load.
connections on the batteries.
With the heater “OFF”, measure the voltage. Then
switch the heater “ON” and measure the voltage 1. Check current draw on the red POSITIVE wire with
again. If the voltage drop is more than one volt, the heater NOT running. Should read 80 to I00 mA.
check the battery connections and the power
connection at the PCM. 2. Check current draw on the red POSITIVE wire with
the heater running in full output, ignition “OFF”. The
If the measured voltage is higher than the specified reading should be 6.5 to 7.5 Amps.
range, check the voltage regulator.
3. Check current draw on the black NEGATIVE (---)
NOTE: If the vehicle batteries are marginal, starting wire with the heater NOT running and the red
the vehicle while the heater is running may: POSITIVE (+) wire disconnected. Should read 0
a. Drop the voltage enough to cause a voltage error mA. This test confirms whether or not there is a
b. Cause random component errors (brown out) power leakage from the vehicle through the heater.

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HEATER VOLTAGE MEASUREMENT positive terminal is always hot relative to the heater
The Proheat auxiliary heater is powered from the 24 chassis ground as long as power is connected to the
volt side of the coach electrical system. The ignition coil heater.

Attach Multimeter Ground (-- ) Lead Here

Ground Wire Test Procedure

From PCM 1. Pull back the rubber boot on the end of the ignition
coil to expose the positive and negative terminals.
2. Select the DC volts range of a multimeter and con-
Heater Chassis
Ground Boss
nect as shown. The positive lead of the multimeter
should be attached to the positive coil lead. Attach
the multimeter negative lead to the heater chassis
at the Proheat ground boss as shown above.
3. Read the voltage with the heater running or trying
to run.

Normal Voltage Range

24 volt heater --- 20.0 to 30.0 volts

FIGURE 21 -- Heater Voltage Measurement

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COMPONENT FAULT DIAGNOSTICS

6. FLAME SENSOR
The flame sensor is an optical device which “sees”
the flame. A FLAME SENSOR diagnostic code indicates
an electrical short circuit in the flame sensor wiring or a
flame sensor failure.
If the sensor lens is dirty or has an open circuit, it can
not “see” the flame and results in either a START or a
FLAME OUT diagnostic code to display.

COMPONENT DIAGNOSTICS 2. Inspect the flame sensor lens for cleanliness.

Check: Flame Sensor 3. Test the flame sensor. Follow the Flame Sensor
1. Inspect the flame sensor wiring for a short circuit. Diagnostic Chart.

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FIGURE 22 -- Flame Sensor Diagnostic Flow Chart

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7. TEMP SENSOR
A TEMP SENSOR diagnostic code indicates a short
or open circuit in the temperature sensor wiring or the
coolant temperature is out of range--- below ---58_ F
(---50_ C) or above 266_ F (130_ C). The resistance of
the temperature sensor is proportional to temperature.

Check: Temperature Sensor (CODE indicated) 2. Test the sensor.

1. Inspect wiring for short or open circuits.

Polarity
Not Important
Temperature Sensor Test Procedure:
Connect a multimeter (adjusted to measure
resistance) to the temperature sensor. Sensor
connector polarity is not important when con-
necting the multimeter test leads.

NOTE: At room temperature -- 70_ F (20_ C)

Resistance is 95O Ohms.
At boiling water temperature -- 212_F (100_C)
Sensor
Connector Resistance is 1700 Ohms.

FIGURE 23 -- Temperature Sensor Test

Test Procedure Guidelines: 3. in boiling water.

Measure the sensor resistance against temperature Compare the measured values against the “Coolant
under the following conditions: Temperature Sensor Graph”. If values do not
1. at room temperature approximately match, replace the sensor.
2. in a freezer

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FIGURE 24 -- Coolant Temperature Sensor -- Temperature/Ohms Graph

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8. FUEL PUMP
The PROHEAT X45 gear-type fuel pump is driven
by the compressor motor through a drive coupling.
The fuel pump is not monitored electrically. A Fuel
Pump diagnostic code indicates a fault in the PCM or
the main wire harness connector.

Fuel Pump Faults

A short or open circuit fault in the fuel pump
drive motor is indicated by a Compressor diag-
nostic code.
A mechanical fault within the fuel pump such
as stripped drive couplings, jammed gears or a
Compressor
faulty pressure relief valve, is indicated by:

Relief Valve S Start diagnostic code flashing. --- Refer to the

“START Function Diagnostics” and follow
Pressure Adjusting Screw
the logic-solution checks.

S Flame Out diagnostic code flashing. --- Refer

to the “FLAME OUT Function Diagnostics”
Drive Couplings and follow the logic-solution checks.
O-- Ring
S Blown fuse in the PCM. Indicates the pump is
seized.
Refer to Component Fault Diagnostics,
Outlet Fuel Pump Figure 32 ---Blown Fuse Test Sequence Chart.
Fitting

Inlet Check: Fuel Pump

Fitting 1. Relief valve for contamination.
Filter
Element Mounting 2. Filter for contamination.
Adaptor Bolts 3. Drive couplings.
Check: Fuel System
1. Refer to the “FUEL SYSTEM DIAGNOSIS”
and follow the logic-solution checks.

FIGURE 25 -- Fuel Pump/Compressor Checks

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9. COMPRESSOR
A COMPRESSOR diagnostic code indicates an open
circuit in the wire harness, a short in the wire harness
between the positive and negative leads or an internal
short in the motor.

NOTE: The Proheat PCM uses “ground-side” switch-

ing for this component. The positive wire to the motors
and ignition coil will show voltage even when the
heater is switched “OFF”.

Symptom: Air Compressor not running

(flashing code Indicated)

Check: Air Compressor Wiring & Function 2. The connector pins for damage or corrosion.
1. That compressor is connected to harness correctly. 3. Harness for pinched or abraded wires.
Refer to the Proheat Electrical System Schematic, in 4. Test compressor. If it tests OK replace PCM. Refer to
Section 7 - Electrical. Figures 26 and 27.

Test Procedure:
1. Apply 24 Volts power to the air compressor and
see if the motor runs. If not, replace the compres-
sor.
2. Measure air compressor motor resistance. Use a
multimeter to measure the resistance across the
Multimeter & compressor connector pins. If resistance shows
Test Leads
an open or short circuit, replace the compressor
assembly.
3. Measure air compressor current. Use the Main
Harness Test Lead as described in “Special Ser-
vice Tools” heading. This Test Lead is used to ap-
ply power from a remote source, to check internal
resistance and to connect a multimeter to check
voltage and amperage.
Compressor
Connecting Pins CURRENT DRAW (Amps) for the Proheat X45---24 is
1.50 --- 3.00 @ 24 Volts.

FIGURE 26 -- Compressor Test

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Compressor
Adjusting Screw Detail - End View
Cover & Bolts
Compressor To Increase
Pressure -
Turn Left

To Decrease Line Nozzle Air Inlet

Pressure -
Turn Right

Adjusting Screw
Electric
Motor

Fuel
Pump Test Gauge
Line From Compressor

NOTE: Pressure Reading for X45 is 6.5 psi.

FIGURE 27 -- Compressor Air Flow & Pressure Test

Symptom: Air compressor running (No 2. Check the blower.

Flashing Fault Code indicated). No air flow or 3. Check the fuel regulator.
low air flow
4. Check fuel system.
Check: Air flow using the PROHEAT pressure
gauge (PK0060) or equivalent. Ensure that the Pressure adjustment:
gauge is accurate (0 -- 15 psi). 1. Locate adjusting screw on the compressor head as
shown in Figure 27.
Procedure: Install the pressure gauge as
shown in Figure 27. 2. Adjust as necessary. Ensure that the voltage is
nominally 24 volts.
NOTE: Pressure Reading for X45 is 6.5 psi.
Symptom: Air compressor running (No
Flashing Fault Code indicated). Fuse blown in
High pressure reading Indicates: PCM
Refer to Figure 35 ---Fuel Nozzle Components &
Maintenance. Check: Air Compressor operation
Refer to Component Fault Diagnostics ---8. Fuel Pump,
1. Blocked nozzle. Air passage only.
Figure 25 ---Fuel Pump/Compressor Checks & 9.
2. Compressor is out of adjustment. Readjust the Compressor, Figure 26 ---Compressor Test.
compressor using the pressure adjustment screw
1. Harness for pinched or abraded wires. The positive
as indicated in Figure 27.
wire must not short to ground.
Low pressure reading Indicates: 2. Motor for internal short.
1. Pinched or leaking air line from the compressor 3. Check for seized motor or fuel pump.
outlet fitting to the fan end inlet.
2. Plugged compressor inlet filter. Retest with the filter
removed. WARNING
Normal reading but a rich or lean flame:
Refer to Fuel System Diagnostics --- Nozzle. Disconnect the PCM electrical power prior to
trying to turn the compressor counterweight
Refer to Component Fault Diagnostics --- 12. Blower. by hand.
1. Check for contaminated nozzle, fuel passage.

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10. IGNITION COIL

An IGNITION COIL diagnostic code indicates an open
circuit in the wire harness, a short in the wire harness
between the positive and negative leads or an internal
short in the coil. The fuse will blow if there is a short to
ground in the positive lead or the coil. The ignition coil
is the easiest place to measure the voltage on the
heater.
NOTE: The Proheat PCM uses “ground-side”
switching for this component. The positive wire to
the motors and ignition coil will show voltage even
when the heater is switched “OFF.”
Symptom: No spark at the electrode –
Flashing Fault Code Indicated

Check: Coil wiring the electrode.

1. Inspect the wiring harness to ensure the ring 2. Inspect the ground lead between the second
terminal connectors are tight on the coil posts. electrode and the heater chassis.
Make sure the polarity is correct. 3. Is the electrode gap adjusted correctly?
2. Inspect for broken or abraded wires in the wire Refer to Figure 37 ---Electrode Gap Setting
harness.
3. Test the Ignition Coil as shown in Figure 28.
4. If an IGNITION COIL diagnostic code occurs and no
fault is found in the coil and wiring, check the PCM.
WARNING
Symptom: No spark at the electrode – NO code The Proheat chassis is grounded from the
Indicated PCM as shown in Figure 28. Ensure the
ground is securely connected. Improper
Check: High tension wires and electrode grounding may result in electrical shock.
1. Inspect the high tension lead between the coil and

PCM Ground Wire

Heater Chassis
Ground Boss

Test Procedure.
Measure ignition coil resistance. Use a multimeter to
measure the resistance across the positive and neg-
ative terminal posts. The resistance should be less
than I ohm. If resistance is “open circuit” or 0 ohms
(short circuit), replace the ignition coil.
NOTE. Remove positive and negative wires
from the coil when testing.

FIGURE 28 -- Ignition Coil Resistance Test

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11. COOLANT PUMP

A COOLANT PUMP diagnostic code indicates an
open circuit in the wire Pump harness, a short in the wire
harness between the positive and negative leads or an
internal short in the motor.
The coolant pump is not self-priming: Ensure that the
coolant system has been purged of air by running the
vehicle engine for at least ten minutes following installa-
tion or service. (DO NOT run dry.)
NOTE: The Proheat PCM uses “ground-side” switch-
ing for this component. The positive wire to the
motors and ignition coil will show voltage even when
the heater is switched “OFF.”

Symptom: Coolant pump not running (Flashing must not short to ground.
Fault Code Indicated)
2. Check motor for internal short, Figure 29.
Check: Coolant Pump wiring & function
Refer to Figure 29 and also to the Proheat Electrical
System Schematic, in Section 7 - Electrical. Symptom: Coolant pump not pumping (No
Flashing Fault Code Indicated)
1. That coolant pump is connected to harness
correctly. (See PROHEAT Wiring Diagram).
2. The connector pins for damage or corrosion. Check: Coolant pump function
3. Harness for pinched or abraded wires. 1. If the impeller is turning freely. If not, replace pump.
4. Test pump. If it tests OK, replace PCM. (See Figure
5---13 and Test Procedure.)
Symptom: Coolant pump leaking
Symptom: Coolant pump not running (No
Flashing Fault Code Indicated). Fuse blown In
PCM Check: Leak location
1. Hose clamps. Tighten if required.
Check: Coolant pump function
1. Harness for pinched or abraded wires. Positive lead 2. Pump housing seal. Replace pump if required.

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Test Procedure:
1. Connect the coolant pump directly to 24 volts out-
put and see if it runs. If not, replace the pump.
2. Measure coolant pump motor resistance. Using a
multimeter, measure the resistance across the
coolant pump connector pins. If resistance shows
an open circuit or an internal short circuit, replace
the coolant pump.
3. Measure coolant pump current. Use the Main Har-
ness Test Lead as described in “Special Service
Tools” heading.
CURRENT DRAW (AMPs) for the Proheat X45 Coolant
Pump is 0.75 --- 2.00 @ 24 Volts

FIGURE 29 -- Coolant Pump Test

12. BLOWER
A BLOWER diagnostic code indicates an open circuit
in the wire harness, a short in the wire harness between
the positive and negative leads or an internal short in the
motor.
NOTE: The Proheat PCM uses “ground-side” switch-
ing for this component. The positive wire to the
motors and ignition coil will show voltage even when
the heater is switched “OFF”.
NOTE: The PCM has an RPM check which measures
the blower RPM. An error code flashes if the blower
speed falls below the RPM required to maintain
sufficient combustion air.

The connector pins for damage or corrosion. c)

CAUTION Harness for pinched or abraded wires.
Test blower. If it tests OK replace PCM. Figure 30.
When a blower fails, the combustion cham- Symptom: Blower not running (No Flashing
ber must be checked for carbon build up Fault Code Indicated) Fuse blown In PCM
and cleaned as necessary.
Check: Blower function
Harness for pinched or abraded wires. Positive lead
must not short to ground.
Symptom: Blower not running (code Indicated) Check motor for internal short. Figure 30.
Check: Blower wiring & function Symptom: Blower turning slowly (No Flashing
Refer to Figure 30 ---Blower Test and also to the Fault Code Indicated)
Proheat Electrical System Schematic, in Section 7 - Check: Blower function
Electrical. For fan blade rubbing on housing.
That blower is connected to harness correctly For fan blade slipping on motor shaft.

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Test Procedure:
Connect the blower to a power supply of the rated
voltage. Does it turn? If not, replace the blower.
Measure the blower motor resistance. Using a
multimeter, measure the resistance across the blower
connector pins. If resistance shows an open circuit or
an internal short circuit, then replace the blower as-
sembly.
Measure blower current. Use the Main Harness
test lead described in “Special Tools” heading.
CURRENT DRAW (Amps) for the Proheat X45
Blower is .5 --- 1.0 @ 24 Volts.

FIGURE 30 -- Blower Test

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MECHANICAL COMPONENT FAULT DIAGNOSTICS

MECHANICAL FAULTS “Component” Symptom following the Logic-Solution
procedures will point to the mechanical problem that
The mechanical systems or components covered in
caused the Error/Fault code to flash.
this Troubleshooting/Analysis heading are not
monitored electrically by sensors. Problems with these Mechanical Systems & Components
components may affect a system or component that is The Fuse, Electrode Gap, Fuel System, including the
monitored by a sensor, resulting in an “ERROR” or Fuel Nozzle and Fuel Regulator are covered in this
“FAULT” code to flash. Diagnosing the “Function” or section.

Fuse Ground on
Heat Exchanger

Fuse
Check the fuse in the PCM If the heater does not run
and the “ON” LED does not light when the heater is
switched “ON”.
The fuse will blow if there is a short to ground in a
positive lead or internally with the following compo-
nents:

S ON/OFF Switch S Coolant Pump S Blower

S Air Compressor S Ignition Coil
Reversing polarity at the battery (power) circuit will
blow the fuse. This will not damage the PCM.

Pin Locations Moulded Into Connector

321

Harness to
Components Coil

321 Compressor
Blower
Coolant Pump

FIGURE 31 -- Internal Wire Harness (Blowing Fuse) Test

Check: Heater wiring Follow the Blown Fuse Test Sequence in the following
Check polarity of battery connections. Flow Chart. Do the tests with power connected and the
Test the internal wire harness for short circuits. PROHEAT switched “OFF”.

CAUTION
Repeated replacement of the fuse or using
incorrectly rated fuses without correcting
the problem can damage the PCM. Use only
a 15 amp fuse.

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FIGURE 32 -- Blown Fuse Test Sequence Chart

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Air Filter
Air Compressor

Compressed Air - 6 to 8 PSI

Reference: Electrode

Nozzle

Fuel Pump

Fuel Inlet

0 - 1 PSI Suction
(from regulator)
Fuel Pick-Up

Fuel Pressure (to regulator) 5 PSI

Fuel Regulator

Fuel Tank

FIGURE 33 -- Fuel System Schematic

FUEL SYSTEM DIAGNOSTICS No --- go to step 3.

Follow this logic-solution procedure to check the fuel S Is the Ignition spark turning “OFF”?
system if a problem is suspected. The Proheat Yes --- then the Flame Sensor sees a flame.
diagnostic Function or Component LEDs affected by a
fuel problem will flash an Error or Fault code. Refer to the No --- then the flame is either too weak or the Flame
Fuel System schematic to identify the major system Sensor and/or circuit is faulty
components. Refer to Component Diagnostics --- 6. Flame Sensor
and Figure 22 Flame Sensor Diagnostic Flow Chart.
Step I: Is there fuel in the tank?
Step 2: Start the PROHEAT. Step 3: Does the Fuel Pump work?
The heater will try to start twice. Wait until it has gone This component must be tested before proceeding
through two cycles (approx. 10 minutes). The PROHEAT with further troubleshooting.
diagnostic system will tell you what it thinks is wrong. S Disconnect the fuel line at the inlet to the regulator.
While it is running observe for: Start the PROHEAT. Check fuel flow. Approx. 1/2
S Is there a flame? liter in 60 seconds.
Yes --- means there is ignition and fuel. S Run the fuel pump by connecting remote power to
See “is the ignition spark turning OFF?” the compressor motor and checking for fuel flow.

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Step 4: Does the Regulator work? NOTE: A regulator that is stuck open will produce a
S Disconnect the fuel line at the fuel inlet fitting, hold rich flame. Blockage in the regulator needle valve
the line at the same level as the inlet. Start the seat will produce a lean flame.
heater, there should be no fuel flow. This indicates
that the regulator is holding the fuel pressure.
S Lightly push on the regulator diaphragm (use a Step 5: Does the Compressor work?
blunt tool), fuel should flow from the line. S Check the pressure output.
Refer to Figure 36 ---Fuel Regulator Test. Refer to Component Diagnostics --- 9. Compressor.

Step 6: Isolate the Nozzle and Compressor.

S Disconnect the fuel line at the outlet of the fuel regu-
lator. Submerse this end in a small container of fuel
positioned approximately at the same level as the
regulator center. This isolates the fuel pump and
the regulator from the system. Start the heater. If a
fuel problem still exists, check the Compressor or
Nozzle.
Immerse Outlet Fuel
Line In Container

Have Fuel Container

Centered With
Regulator Center

Remove Fuel Line

From Regulator

FIGURE 34 -- Isolating Fuel Pump & Regulator From The System

Step 7: Is the Fuel Nozzle contaminated? S Clean the nozzle with a cleaner/degreaser, which
S Refer to Nozzle --- Figure 35, Fuel Nozzle will wash contamination out the back end of the
Components & Maintenance. nozzle.

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Stem
No Nicks NOZZLE
In O-Ring
The nozzle (and the compressor) regulate the fuel air
Counter Bore
Distributor mixture. A set orifice size allows a certain amount of fuel
Nozzle and air to flow through the distributor.
Problems in the nozzle can cause poor burning. This
will be indicated by a START or FLAME OUT diagnostic
Turn Clockwise code on the PCM function display.
To Disassemble
Check: Nozzle
Holes & Grooves Clear
1. Inspect the nozzle for blockage.
Apply Compressed 2. Clean or replace nozzle as necessary.
Turn Counter-Clockwise
Air In This Direction To Disassemble 3. Check and clean fuel passage in the fan end.

DISTRIBUTOR CLEANING
NOTE: Clean the distributor counterbore by lightly
0.060” Drill Bit
hand spinning a 0.060” dia. drill bit. Wash with
Distributor cleaner/degreaser. Do not use a tip cleaner in the
fuel orifice (Step 4 - Nozzle Cleaning Procedure).

FIGURE 35 -- Fuel Nozzle Components & Maintenance

Nozzle Cleaning Procedure: 7. Lubricate O-ring with diesel fuel and reinstall nozzle
in fan end.
1. Remove nozzle from fan end.
2. Disassemble nozzle as shown in Figure 35. NOTE: See Figure 34, Step 6 to confirm that the
nozzle is functioning correctly. All nozzle parts are
3. Use a cleaner/degreaser to thoroughly wash the matched. Do not interchange.
separate parts.
4. Dislodging contaminants in the distributor FUEL REGULATOR
counterbore can be done by lightly hand spinning a The fuel regulator reduces the fuel pressure supplied
0.060” dia. drill bit and then washing. Refer to by the fuel pump from 5 psi (0.34 Bar) down to
Figure 35. Do not use a tip cleaner in the fuel orifice. atmospheric pressure (0 --- 1 psi). Compressed air
flowing through the nozzle creates a venturi effect which
5. Reassemble nozzle and torque to 30 inch pounds.
siphons fuel from the regulator. If the compressed air
6. Using compressed air for cleaning should only be flow through the nozzle stops, the regulator closes and
applied in the direction as indicated in Figure 35. shuts off the fuel flow.

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Fuel Regulator
Test Procedure:
Disconnect the fuel line at the nozzle fuel inlet fitting and
place it in a container.
Start the heater. Insert a small blunt pin in the regulator
vent hole and GENTLY depress the diaphragm.
Fuel should flow out of the fuel line. If there is no fuel flow,
the regulator is plugged.
NOTE: If the fuel regulator fails, check the combus-
Vent Hole
tion chamber for carbon build up and clean as
Blunt Pin Depresses
Diaphragm Under Vent Hole
required.

FIGURE 36 -- Fuel Regulator Test

Check: Fuel Regulator 2. Ensure that all fuel line connections are tight. Check
1. Ensure that the vent hole in the regulator is not the clamps.
plugged.

ELECTRODE GAP
The electrode gap is factory set and should not
require adjustment.
Electrode

NOTE: Be careful not to bend the electrode

Nozzle
during servicing. If the electrode is accidental-
ly bent, carefully bend to the correct gap
Combustor setting as shown in this diagram.
Tube

1/4” - 9/32”
Gap

FIGURE 37 -- Electrode Gap Setting

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SERVICE TOOLS
The Special Tools and Test Equipment listed in this section are specially
designed to service the PROHEAT X45 Auxiliary heater. These tools are
available for purchase through Motor Coach Industries, Service Parts
Division and Universal Coach Parts.

Spade Connectors The Proheat Electrical system uses sealed electri-

cal connectors for moisture insulation.
This Test Lead is required for electrical diagnos-
tics and troubleshooting the Proheat electrical sys-
Multimeter Probes tem using these types of connections.
The Test Lead connects a multimeter to the sys-
tem to test internal resistance, voltage , amperage
and continuity. All components can be checked us-
ing this Test Lead except the blower.
A separate power source can be connected to the
compressor and water pump through the Test Lead
spade connectors.
MCI Part No. 16L-16-349

Connect in Series Test Lead

To Test Amps

FIGURE 38 -- Main Harness Test Lead -- MCI Part No. 16L-16-349

The Remote ON/OFF Switch plugs directly into the

PCM Switch Input plug. The Proheat can be turned
PCM Switch Input
OFF and ON at the Proheat unit instead of through the
console switch. The switch cable is 24 inches long.
MCI Part No. 16L-16-350

ON/OFF
Switch
24” Lead

FIGURE 39 -- Remote ON/OFF Switch & Lead -- MCI Part No. 16L-16-350

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AIR COMPRESSOR TEST GAUGE

Air/Fuel Nozzle Inlet The Test Gauge checks for proper air flow and air
pressure from the Air Compressor outlet to the Air/
Fuel Nozzle inlet. The gauge should accurately show
Line to Air/Fuel a pressure reading from 0 PSI to 15 PSI.
Nozzle Inlet The Air Line pressure should read 6.5 PSI. Refer to
“COMPONENT FAULT DIAGNOSTICS”--- 9.Com-
pressor, Figure 27 for Compressor output pressure
test.
MCI Part No. 16L-16-352
Test Gauge

Line From
Compressor
Air Flow Direction

FIGURE 40 -- Air Compressor Test Gauge -- MCI Part No. 16L-16-352

PROHEAT Control
Module (PCM)
DATA LINK KIT
The Data Link Kit downloads data from the PCM
into a computer for viewing. This information is used
Serial Cable for diagnostics and troubleshooting and to find out
the furnace operating time in hours.
Power Cable
The Data Link Kit contains the following:
1. Data Link Software: Two Data Disks,
S 1.4 MB 3-1/2” Disk
9 Pin/25 Pin
Connector S 0.720 MB 5-1/4” Disk
Adaptor
2. Serial Cable-Connects computer to controller
(25’ long)
3. Power Cable (15’ long)
4. 9 Pin/25 Pin Connector Adapter
Required --- But Not Included:
5. IBM-Compatible Computer --- with Serial Port
Data Link Operating
Instructions MCI Part No. 16L-16-351
Lap Top or Data Link Software
Desk Top Disks (3-1/2”/5-1/4”)
Computer

FIGURE 41 -- PROHEAT Data Link Kit -- MCI Part No. 16L-16-351

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SPECIFICATIONS
Description
AUXILIARY HEATER
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Teleflex
Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PROHEAT X45
Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Volts
Volt Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.0 --- 30.0 Volts
Current Draw (Amps) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.75 Amps
Ignition type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Electronic Spark Ignition
Heat Rating --- BTU/Hr (kW) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45,000 (13.0)
Fuel Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Diesel #1, #2, Kerosene
Fuel Flow Rate --- Gal./Hr (L/Hr.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32 (1.2)
Operating Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ---40_F to 122_F (---40_C to 50_C)
Coolant Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150_F to 185_F (65_C to 85_C)
Coolant Flow Rate --- Gal./Min. (L/Min.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.0 (30)

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Printed in Canada.
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 Date March 2003

SECTION 17
LAVATORY

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SECTION 17

LAVATORY
CONTENTS OF THIS SECTION

SUBJECT PAGE
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-2
Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-2
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-3
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-4
Fresh Water Storage Tank . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-4
Soap Dispenser . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-4
Toilet, Drop Tube and Flush Pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-4
Primary Retention Tank . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-6
Secondary Retention Tank . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-7
Slide Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-7
Thermal Drain Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-8
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-11
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-11

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GENERAL DESCRIPTION
The lavatory is located at the curbside rear of the
coach and is entered through the door at the end of the
aisle. The interior surfaces are easily-cleaned, low-
maintenance materials, including stainless steel and
painted fiberglass.
The lavatory has a chemical toilet (flush toilet
optional), a call button and various dispensers. A wash
basin is optional.

COMPONENTS

Dome Light
A microswitch is installed in the door post at the edge
of the front partition. This switch is activated by the door
lock mechanism upon locking to energize the dome light
and the “Washroom Occupied” sign on the outside wall.
The switch is readily serviced by removing the two
screws securing the striker plate to the post.
A 2 candle power light is on when the running lights
are activated and a 6 candle power bulb lights when the
lavatory door is closed and locked.

Door Spring
A spring hinge provides positive lavatory door FIGURE 1
closing. The hinge also reduces rattles and strain on the
lock, striker plates. Retention Tanks
The lavatory’s toilet (whether chemical or flush) uses
two waste holding tanks: a primary and a secondary.
Fresh Water Storage Tank The primary tank has a 16 U.S. gallon (60.5 L) capacity.
A polyethylene fresh water tank for the optional wash The secondary retention tank has a 24 U.S. gallon (90.8
basin is located in the center locker. An overflow tube L) capacity, and is located directly below and connected
located on top of the tank and drains water under the to the primary tank. With the secondary retention tank,
rear of the coach. the operator has additional waste storage when waste
disposal facilities are not available. Both tanks are filled
Towel and Tissue Dispensers with a chemical charge which deodorizes and
A towel dispenser is mounted on the inside of the neutralizes solid waste.
lavatory above the sink, with an opening for a A manually-operated slide dump valve is provided to
“Towelette” wet towel option. These towels can be used drain the primary retention tank. The secondary tank
for washing and drying. A key is furnished for refilling comes with an additional slide dump valve and
dispenser. connecting tube.
Both tanks have 110V AC immersion heaters
Soap Dispenser powered by the station plug-in located on the secondary
A plunger-activated soap dispenser is provided on tank.
the paper towel dispenser above the sink. Lavatory Service Panels
The optional chemical tank flush is located within the
Flush Toilet Pump rear engine door. A Hansen 6000 series quick connector
The optional flush toilet’s air-operated diaphragm is provided for filling the primary waste tank. A remote
pump is a self-contained flushing unit within the flush button is also installed. A separate fresh water fill
toilet/drop tube assembly. The flush system continually service panel is located in the right rear service
recirculates the chemically charged waste water during compartment. A Hansen 5000 connection is also
the self-clean flush cycle. provided for filling of the storage tank.

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Emergency Buzzer travel, air pressure builds in the pump, resetting the flush
The emergency buzzer switch is located above the button. Air which has been trapped between the pump
window. A light on the driver’s instrument panel and the air valve is exhausted through an exhaust valve.
illuminates and a buzzer sounds when the switch is As the air pressure drops, a large spring returns the
pressed. Refer to the wiring diagram for circuit diaphragm to its original position, drawing fluid through
continuity. a pin filter into the pump for the next flush cycle. The
entire flush cycle takes about 5 seconds.
Occupied Sign
A “lavatory occupied” light is located at the top of the
locker in the center aisle, visible from all seating
positions. The sign is a green ISO pictogram that
illuminates when the lavatory is free, and changes to red
(with a diagonal line) when the lavatory is occupied and
locked.

OPERATION
Ventilation System
A 24 V exhaust fan is connected to a duct leading from
the lavatory. The fan runs when the master key is
switched to “ACC” or “RUN.” This discharges stale air
from the lavatory and into the the engine air inlet at the
main filter.
Toilet Flush
The optional flush toilet’s air-operated diaphragm
pump is actuated by the flush button located below the
wash basin side panel. Internal flush and recovery
valves control the flow of waste water into and out of the
pump assembly (Figure 2).
Flush Cycle
When the flush button is actuated, regulated air from Air Flush Pump
the accessory air system flows into the flush pump. The
pump diaphragm is displaced,displacing fluid to rinse FIGURE 2
the bowl. When the pump diaphragm completes its

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 Date March 2003 Page 17-4

MAINTENANCE TOILET, DROP TUBE AND FLUSH PUMP

Removal
FRESH WATER STORAGE TANK 1. Drain and clean out the primary tank (Flush several
cycles with clear water if the flush toilet is installed).
Inspection 2. Remove cover at heat duct outside of the lavatory
and remove access panel for the rinse and flush.
Inspect the tank interior periodically.
3. Undo butterfly clips ¼ turn (4 clips).
4. Pull the cover and toilet seat up. The pump will also
Removal come up. Undo the gray quick connect fitting to the
1. Drain the tank. (Open manual drain valve located in utility panel from the inside of the tank. Adjust pump
the engine compartment). until it comes out of the top of the bench.
2. Open center locker door. Disassembly (Figure 3)
3. Undo plastic clips holding the hose to the barbed
fitting at the bottom of the tap supply.
WARNING
NOTE: To aid the lines though grommets. open the
dispenser in the lavatory and the three lines should be The pump assembly spring is compressed
to 25 lbs. (11.3 kg) pre-load. Exercise care
visible. during disassembly.

4. Undo the 4 bolts under the tank and slide it forward 1. Unfasten and remove the upper and lower pan
aiding lines though grommets. (DO NOT FORCE attachment bolts and break the assembly apart.
may tear lines). 2. Remove the retaining ring securing the comb and
5. Undo plastic clips holding the overflow and fill lines grid.
and remove them from fitting. 3. Remove the cotter pin securing the conical spring.
Remove the spring and comb stem.

Installation 4. Remove the screws securing the pump valve to the

flush outlet port.
1. Reinstall in the reverse order of Removal taking
5. Remove the plate and gasket from the pump valve.
care not to kink the tubes. Refill and check for leaks.
6. Remove the pump valve from the flush outlet port.
7. Remove the spring from the diaphragm retaining
SOAP DISPENSER area.
To refill the liquid soap dispenser: 8. Use the lavatory flush pump repair kit to replace any
damaged parts.
1. Open the main dispenser above the sink by the
keyed-alike lock at the top of the dispenser. Assembly
2. Pull the soap container from the bracket that 1. Reassemble in the reverse order of Disassembly.
attaches it to the coach. Use silicone to seal the diaphragm to the upper and
lower pans. Torque the hex nuts to 10-20 in-lbs.
3. Remove cap and pour liquid soap into dispenser
tank until it is full. 2. Air test the pump assembly and check for leaks.

4. Replace the container into the bracket and close the Installation
main dispenser. 1. Reinstall the flush pump in reverse order of
As part of your regular routine, check the operating Removal. Use silicone to seal the pump gaskets to
condition of the soap dispensing pump mechanism at the tank. Torque the stud ring hex nuts to 10-20
regular intervals to make sure it works freely. If it seems in-lbs.
sticky, disconnect it from the dispenser and allow it to 2. Fill the tank to the sight glass and test the flush
soak in water. Check the operation before reassembling function of the pump assembly and check for tank
into dispenser. leakage.

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1. NUT, SELF LOCKING

2. FLAT WASHER
3. RETAINING RING
4. DIAPHRAGM
5. PAN, SUB-ASSY
6. PAN, AIR SIDE
7. PAN ASSY
8. SPRING
9. NUT, SELF LOCKING

10. COTTER PIN

11. CONICAL SPRING
12. FLAT WASHER
13. V-BAND CLAMP
14. MUSHROOM VALVE
15. PAN, LIQUID SIDE
16. COMB, GRID CLEANER
17. MUSHROOM VALVE
18. SEALING RING
19. FILTER
20. LOCK WASHER
21. FLAT WASHER

Figure 3. Self Cleaning Flush Pump

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 Date March 2003 Page 17-6

PRIMARY RETENTION TANK 5. Close the slide valve handle and recharge the
chemical tank to the sight glass level. Press the
Draining and Recharging flush button to charge the pump with new chemical
NOTE: Use a special hopper or collection point in the solution.
floor of the service area equipped with proper flush
down facilities to dispose of the lavatory system’s NOTE: Pour 1/3 pint (0.15 liters) of Kilgerm or
waste contents. Refer to local health regulations for equivalent disinfectant into retention tank. This
proper disposal procedures and equipment. chemical mixed with water will properly charge the
tank. Refer to the suppliers listing at the end of the
To service the primary tank follow this procedure: section for appropriate disinfecting and deodorizing
1. Drain the primary waste tank by pulling out on the chemicals
handle of the slide dump valve.(Accessible at the
upper right service compartment). Winterizing
2. Press flush button to remove most waste water from The primary tank has an immersion heater powered
tank, and push the slide valve handle in to the by 110 VAC when the in-station power is plugged in. Use
closed position (Figure 4). an anti-freeze solution such as ethylene glycol in the
retention tank with the disinfectant. Based on the
FLUSH expected average low temperature and the quantity of
waste in the retention tank, charge the tank as follows:
RETENTION TANK
(Behind this panel) Percentage of Antifreeze Required in Tank
25% 33% 40% 50%
Protects To: +0_F 0_F -12_F -34_F
(-12_C) (-17_C) (-24_C) (-36_C)

SIGHT GLASS
FILL CAUTION
Do not use automotive “stop-leak” formulas
in the retention tanks. These compounds
Figure 4. Lavatory Service Panel may cause coagulation of the flushing fluid
when mixed with deodorizing additives.
3. Change the tank with fresh water and press flush
button to rinse the tank. Open the slide valve handle
to drain the tank. NOTE: For better odor control increase the amount of
4. Repeat this operation until tank is clear. chemical when used with antifreeze.

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 Date March 2003 Page 17-7

SECONDARY RETENTION TANK Percentage of Antifreeze Required in Tank

25% 33% 40% 50%
Inspection Protects To: +0_F 0_F -12_F -34_F
Inspect the tank interior periodically for foreign (-12_C) (-17_C) (-24_C) (-36_C)
objects or excessive buildup in the tank corners due to
lack of proper rinsing.

Removal CAUTION
1. Turn battery disconnect switch OFF.
2. Disconnect the electrical cable lead from the “+” Do not use automotive “stop-leak” formulas
terminal on the tank. in the retention tanks. These compounds
3. Disconnect the drop tube. may cause coagulation of the flushing fluid
when mixed with high quality deodorizing
4. Disconnect the leads from the 110V in-station additives.
plug-in receptacle.
5. Remove the stainless steel under-pans which
protect the belly of the tank. NOTE: For better odor control increase the amount of
chemical when used with antifreeze.
6. Disconnect the clamps which hold the tank in place
and lower the tank to the floor.

Draining and Recharging

NOTE: Use a special hopper or collection point in the
floor of the service area equipped with proper flush
down facilities to dispose of the lavatory system’s
waste contents. Refer to local health regulations for
proper disposal procedures and equipment.

Figure 6. Slide Dump Valve Handle for Primary

Retention Tank

SLIDE VALVE
Two manually-operated slide dump valves (knife
gates) are provided: one to drain the primary retention
tank and one to drain the secondary retention tank. To
drain the primary tank pull out on the handle of the slide
valve (Figure 6). To drain the secondary tank move the
Figure 5. Secondary Retention Tank Cleanout lever to the right.

NOTE: Slide valve handle-to-shaft connections can

Installation be either pinned or threaded.
1. Install in the reverse order of Removal.
Removal
Winterizing
1. Drain and clean the tanks as described in Draining
The primary tank has an immersion heater powered
and Recharging.
by 110 VAC when the in-station power is plugged in. The
secondary tank also has a 110V AC heater. Use an 2. Unfasten clamps that hold the connector hose to
anti-freeze solution such as ethylene glycol in the the drop tube. Remove drop valve.
retention tank with the disinfectant. Based on the 3. Unfasten the 4 bolts that holding the hub and valve.
expected average low temperature and the quantity of Pull valve off.
waste in the retention tank, charge the tank as follows: 4. Inspect the gaskets and replace them if necessary.

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 Date March 2003 Page 17-8

Installation Removal
1. Install in the reverse order of Removal. Make sure 1. Drain the tank completely.
that the flow direction is down. 2. Unfasten and remove the valve from the bracket.
THERMAL DRAIN VALVE
Disassembly
The optional thermal drain (Ozontz) valve
automatically drains the fresh water storage tank when 1. Remove the cap, thermal unit, cage, operating
the temperature in the vehicle drops to approximately spring and bearing plate.
34_F (1_C). The valve is mounted to a bracket located 2. Clean the seat at the bottom of the valve body.
below the wash basin (Figure 7). This valve is a basic 3. Reassemble the bearing plate, operating bearing
component with the wash basin option. spring, cage, thermal valve unit and cap, making
certain that the cage is properly aligned with the
Inspection & Testing valve port and that the cage assembly is not
It is recommended that the thermal drain valve be cocked.
inspected for leakage at the outlet port located in the If the valve still leaks:
engine compartment once a year, preferably in the fall.
Use the following procedure. If there is no leak with the
4. Remove the cap, thermal unit and cage.
temperature above 40_F(4_C), the valve is satisfactory
and needs no servicing. If a leak is evident, repair or 5. Remove the valve guide and poppet from the cage.
replace the valve. 6. Install a new Buna S poppet and re-install the guide.
The thermal drain valve can be easily tested for 7. Re-install the cage and a new thermal unit.
accuracy. The following method is recommended for 8. Re-install the cap, making certain that the cage is
testing thermal drain valves: properly aligned with the valve port and that the
cage assembly is not cocked.
1. After the thermal drain valve has been at room
temperature for at least one half hour, pour 45_F Installation
(7_C) or warmer water into the inlet of the valve. The 1. Install in the reverse order of Removal. Refill and
valve should be closed and no water should flow. check for any leaks.
2. Place the thermal drain valve in a container of ice or
water and cover it. The water should be about 33_F NOTE: In case of a complete replacement of the
(1_C). drain valve, make sure to seal around the outlet port in
3. After at least one half hour, remove the valve and the engine compartment with mortite tape to prevent
pour water into the inlet port. Water should flow engine compartment fumes from entering the
through the valve’s outlet port. lavatory compartment.

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CAP & ADJUSTING POPPET

SCREW
VALVE GUIDE
GASKET

OPERATING SPRING

THERMAL UNIT
BEARING PLATE
LARGE

BODY
CAGE

6934

Figure 7. Thermal Drain Valve

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Date March 2003 Page 17-10

1. FRESH WATER SUPPLY LINE

2. FLUSH REGULATOR
3. DRAIN VALVE
4. SERVICE HARNESS FLUSH PANEL
5. AIR SUPPLY LINE
6. OVERFLOW VALVE
7. FRESH WATER FILL VALVE
8. SERVICE FLUSH PANEL
9. FRESH WATER SUPPLY VALVE
10. QUICK RELEASE VALVE
11. FRESH WATER OVER FLOW VALVE
12. FRESH WATER FILL LINE
13. FAUCET
14. MANUAL SHUT OFF LINE
15. DRAIN
16. P. TRAP
17. DRAIN HOSE
18. PRIMARY LAV. TANK
19. FRESH WATER TANK
20. SINK
21. TOILET SEAT
22. BOWL ASSEMBLY
23. FRESH WATER SUPPLY LINE (PUMP)
24. FLUSH PUMP
25. FRESH WATER SUPPLY LINE (BOWL)

Figure 8. Lavatory Plumbing

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 Date March 2003 Page 17-11

TROUBLESHOOTING
Toilet will not flush Pushbutton will not reset, air leading Air line from pump assembly to control valve
can be heard. broken or disconnected, or cracked or broken
lower pan housing. Air lines may be connected
backwards.
Air regulator hissing. Defective air regulator.
Water in the air line from the pump Pump diaphragm broken.
to the pushbutton.
Comb stuck in up position. Replace the comb and grid, or replace the
conical spring if it is broken.
Pump is functioning, but no water in Broken water line from the pump assembly to
bowl. the bowl.
Short flushing cycle (10 Bubbles in the flush pattern.
seconds optimum)
Hole in the water hose from pump assembly to
bowl.
Comb will not reach full height dur- Excessive build-up of debris between pins of
ing flush cycle. comb.
Water bubbling in grid area. Defective valve in the comb housing area.
Air bubbles in the flush Water level below comb pins. Recharge with water and chemical DG-19C.
Insufficient amount of water pre-charge.
Water in the air line from pump to pushbutton.
Small hose in the pump diaphragm.

SPECIFICATIONS
PRIMARY RETENTION TANK ASSEMBLY
Manufacture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MCI
Capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 U.S. gals. (60.5 liters)
SECONDARY RETENTION TANK ASSEMBLY
Manufacture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MCI
Capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 U.S. gals. (90.7 liters)
SLIDE DUMP VALVE (PRIOR TO UNIT # 60794)
Manufacture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Valtera
FRESH WATER STORAGE TANK ASSEMBLY
Manufacture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MCI
Capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 gals. (37.8 liters)
LAVATORY SERVICE PANEL VALVES
Manufacture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hansen

MOTOR COACH INDUSTRIES

Printed in Canada.
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 Date March 2003

SECTION 22
WHEELCHAIR LIFT

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Printed in Canada.
 Date March 2003 Page 22A-1

SECTION 22A
STEWART & STEVENSON
WHEELCHAIR LIFT
CONTENTS OF THIS SECTION
SUBJECT PAGE
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22A-2
Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22A-2
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22A-3
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22A-3
Torque Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22A-4
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22A-5

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 Date March 2003 Page 22A-2

GENERAL DESCRIPTION Lift Platform

A Stewart and Stevenson wheelchair lift is installed in The wheelchair lift platform features:
the storage compartment on the curbside rear of the S Folding handrails,
coach between the wheel housing and the rear service S A manually-operated front barrier, and
door. The lift platform extends and lowers to ground S A powered rear barrier that acts as a bridge between
level, allowing wheelchair access. The platform raises to the platform and the coach floor.
coach floor level where the passenger enters the coach
through the cabin access door. Coach Seating
The lift is powered by an electrically-operated The coach can accommodate two wheelchair-bound
hydraulic pump, with manual backup, and operated with passengers, one on each side at the rear of the coach,
a hand-held controller. Keyed access and a safety by repositioning the sliding and folding seats.
interlock prevent unsafe deployment. A seven-point wheelchair and passenger restraint
system is provided at each of the wheelchair locations.
COMPONENTS
Cabin Access Door
A cabin access door is located directly above the
SLIDING & LAP/SHOULDER
wheelchair lift storage compartment. The door has a FOLDING BELT
forward hinge and a positive lock mechanism to prevent SEAT
accidental closing. It is operated manually.
Hydraulic System
The hydraulic system consists of five cylinders, a
cross-port relief valve, a hydraulic manifold equipped
with four function valves, and a power pack that consists
of the reservoir and pump. The lift is activated by
switches on a hand-held controller. If there is an
electrical failure, the function valves can be operated
manually.

HYDRAULIC
CONTROL
BOX

FIGURE 2

PUMP &
RESERVOIR
ASSEMBLY

LIFT PLATFORM
CONTROLLER
HAND RAIL

WHEELCHAIR LIFT IN STOWED POSITION

FIGURE 1

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Printed in Canada.
 Date March 2003 Page 22A-3

OPERATION 1. Inspect for loose or missing attaching hardware.

To operate the wheelchair lift, the transmission must Tighten or replace as required.
be in neutral, the park brake applied and the wheelchair 2. Inspect hoses and fittings. Replace damaged hose
lift master key switched on. assemblies.
The wheelchair lift platform is deployed manually. The 3. Inspect hydraulic cylinders for leaks. A small
operator unfolds the platform and handrails. amount of oil on the piston shaft is acceptable. If
leaks are detected, install new seal kit or replace
Once the platform is deployed, the lift is operated
cylinder as required.
electro-hydraulically using functions on the hand-held
controller: extend, retract, raise, lower, and bridge (the 4. Check the hydraulic reservoir fluid level. Fill as
rear barrier folds out to create a ramp from the platform required.
to the coach floor). If there is an electrical failure, a 5. Inspect the power units for leaks. Repair as
secondary manual system can be used. required.
For more information, see the Operator’s Manual, the 6. Test the operation of the hand pump.
Stewart and Stevenson Manual and the Stewart and 7. Check non-skid surfaces for excessive wear or
Stevenson decal mounted on the inside of the loose edges. Repair or replace as required.
wheelchair lift compartment door. 8. Following correct safety and operating procedures,
cycle the lift to ensure proper operation.
NOTE: Inspect and operate the lift daily as part of the
coach’s pre-run inspection. See the Operator’s
Manual.
Do not use the wheelchair lift for lifting
freight. The warranty will be void.
LUBRICATION
A light coat of oil should be applied to the chain
located inside the moving frames every 12 months or
MAINTENANCE whenever the chain is detached or handled. The amount
of oil and the service interval may vary depending on use
Wheelchair lift maintenance is described in the and conditions.
Stewart and Stevenson Manual. Follow the safety
guidelines, maintenance procedures and maintenance HYDRAULIC RESERVOIR
requirements given in the Stewart and Stevenson Every 500 operating hours or when contamination is
manual. suspected:
1. Inspect the intake tube screen filter.
INSPECTION
2. Change the hydraulic fluid.
Prior to operating the lift, during repair procedures
and as part of the coach’s routine maintenance NOTE: Whenever the system is opened and drained,
schedule, inspect the lift. bleed the system after filling.

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Printed in Canada.
 Date March 2003 Page 22A-4

TORQUE CHART

1
1
1
1

1
1
1
1

Torque Chart
Torque Value Range

Item Description Size Lb-Ft N.m

1 CAPSCREW 1/2---13 X 1.5 75 101.7

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page 22A-5

SPECIFICATIONS
Wheelchair Lift Assembly

Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stewart & Stevenson Power, Inc.

Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 590 lbs
Lift Capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 600 lbs
Platform Width . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.5 in.
Platform Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 in.
Outer Barrier Height . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 in.
Stowed Dimensions (H x W x D) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 x 37.5 x 18 in.
Vertical Travel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 in.
Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 volt

MOTOR COACH INDUSTRIES

Printed in Canada.
 6(59,&( %8//(7,16
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 Date March 2003 Page Index-1

ALPHABETICAL INDEX

A Air Fill Provisions, 4A-6

Air Horn, 4D-14
ABS Valve, 4A-3, 4D-10 Air Manifold, 4A-3
Accelerator Pedal, 9B-1 Air Schematics, 4F-1
Installation, 9B-3
Removal, 9B-3 Air Spring Maintenance, Front Axle Suspension, 12B-8
Specifications, 9B-3 Air Systems, 4A-1
AD ---IP Air Dryer, 4C-1 Air Dryer, 4A-2, 4C-1
Air System Overview, 4A-2 Air Manifold, 4A-3
Assembly, 4C-7 Brake Chambers, 4A-5, 4E-2
Cleaning and Inspection, 4C-5 Compressor, 4A-2, 4B-1
Dryer Removal, 4C-4 Cooling Coil, 4A-2
Installation, 4C-7 Fill Provisions, 4A-6
Operation & Leakage Tests, 4C-3 Governor, 4A-2, 4B-1
Rebuilding the AD ---IP Air Dryer, 4C-4 Junction Blocks, 4A-5
Troubleshooting, 4C-8 Oil Separator, 4A-2, 4C-1
Pressure Transducers, 4A-6
Air Cleaner - Dry Type, 9C-1 Reservoirs, 4A-2, 4A-3
Installation, 9C-2 Service Brake Systems, 4A-6, 4E-2
Air Compressor, 4B-1, 4B-2 Switches, 4A-5, 4A-6
Air System Overview, 4A-2 Towing Provisions, 4A-6, 4A-7
Specifications, 4B-18 Valves, 4A-2, 4A-3, 4A-4, 4A-5
Torque Specifications, 4B-17 Alarms and Signals, 7D-1
Troubleshooting, 4B-10 Alarm Buzzers, 7D-2
Air Conditioning (See Heating and Air Conditioning), Horns, 7D-2
16A-1 Specifications, 7D-3
Air Control Components, 4D-1 Allison (see Automatic Transmission), 13A1-1
Air Horns and Valve, 4D-14 Alternator, 7A-6, 7B-1, 7B1-1
Antilock Valve, 4A-3, 4D-10 Assembly, 7B-9
Brake Pedal Assembly, 4D-5 Disassembly and Testing, 7B-3
Brake Valve, 4A-3, 4D-3 Removal, 7B-3
Double Check Valve, 4A-4, 4D-12 Specifications, 7B-12
Emergency Release Valve, 4A-4 Torque Chart, 7B-12
Entrance Door Valves, 4A-5 Antifreeze, 6C-5
Low Pressure Switch, 4D-13
Park Valve, 4A-4, 4D-2 Arvin, (see Slack Adjusters, Meritor), 4E-13
Pressure Protection Valve, 4A-2, 4D-11 Automatic Transmission (B-500 & B-500R), 13A1-1
Pressure Regulator, 4D-12 Components, 13A1-2
Pressure Transducers, 4A-6, 4D-13 Filter, 13A1-6
Quick Release Valve, 4A-3, 4D-5 Fluid Check, 13A1-3, 13A1-4
Reservoirs, 4A-2, 4A-3, 4D-11 Inspection, 13A1-3
Service Brake Relay Valve, 4A-3, 4D-8 Lubrication, 13A1-3, 13A1-5
Spring Brake Relay Valve, 4A-4, 4D-6 Removal, 13A1-7
Air Dryer, 4C-1, 4C-2 Specifications, 13A1-8
Air System Overview, 4A-2 Torque Chart, 13A1-8
Maintenance, 4C-3 Automatic Transmission (ZF As---Tronics), 13A2-1
Rebuilding the Air Dryer, 4C-4 Function/Error Displays, 13A2-4
Specifications, 4C-14 Lubrication, 13A2-7
Troubleshooting, 4C-8 System Error codes, 13A2-7

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Printed in Canada.
 Date March 2003 Page Index-2

Transmission Operation, 13A2-5 Specifications, 4E-28

ZF---As---Tronics Diagnostics Codes, 13A2-9 Brake Pedal Assembly, 4D-5
Auxiliary Heater (see Proheat), 16B-1 Brake Valve, 4A-3, 4D-3
Axle Brakes, 4E-1
Front, 1-1 also see Brake Chamber, 4E-2
Tag, 1-1, 2B-1 also see Drum Brakes, 4E-17
Axle Alignment Procedure, 2C-1 also see Slack Adjusters, Haldex, 4E-9
also see Slack Adjusters, Meritor, 4E-13
also see Spring Brake, 4E-2, 4E-7
B Brake Burnishing, 4E-25
Function Test, 4E-25
Baggage and Service Compartment Doors Specifications, 4E-28
Components, 3C-10 Torque Chart, 4E-26
Engine Service Doors, 3C-10 Troubleshooting, 4E-27
Inspection, 3C-10 Bumpers, 3A-3, 3A-11
Installation, 3C-11 Buzzer, 7D-2
Locking System, 3C-10 Lavatory Emergency, 17-3
Maintenance, 3C-10
Removal, 3C-11
Service Tools, 3C-13
Baggage Door, 3C-10
C
Caterpillar C12 Engine (See Engine, Caterpillar),
Batteries, 7A-6, 7E-1
8A2-1
Auxiliary 12 Volt Power, 7E-6
Battery Box, 7E-2 Central Tunnel, 3A-2
Battery Charging, 7E-3 Chamber, Brake, 4A-5, 4E-2
Battery Disconnect, 7E-2
Battery Equalizer, 7E-7 Charging, Batteries, 7E-3
Battery Failure, 7E-3 Check Valve, Two Way, 4A-4
Boosting, 7E-5
Circuit Test Equipment, 7A-6
Cleaning and Inspection, 7E-2
Electrolyte Specific Gravity Check, 7E-3 Clamps and Hoses, 6B-5
Removal, 7E-7 Cleaning, Exterior, 3A-3
Specifications, 7E-8
Testing, 7E-4 Clutch Fan Assembly, 6A-3

Blinds Coatings, Exterior, 3A-2

Manual Window Blinds, 3D-5 Cold Weather Starting, 8B-1
Passenger, 3D-5 Auxiliary Heater, 8B-1
Block Heater, 8B-1
Block Heater, 8B-1
Components
Body, 3A-1
Exterior, 3A-1
Frame, 3A-2
Interior, 3B-1
Reference Chart, 3A-15
Compressor, Air System, 4B-1, 4B-2
Booster Cables, Connecting/Disconnecting, 7E-5
Air System Overview, 4A-2
Bosch, (see Alternator), 7B-1, 7B1-1 Maintenance, 4B-4
Brake Chamber, 4A-5, 4E-2, 4E-6 Operation, 4B-3
Assembly, 4E-6 Coolant, 6C-1
Components, 4E-2 Antifreeze, 6C-5
Disassembly, 4E-6 Coolant Additive Values, 6C-4
Leak Test, 4E-5 Coolant Requirements, 6C-3
Operation and Pushrod Travel Inspection, 4E-4 Corrosion Inhibitors, 6C-5
Parts Inspection, 4E-6 Daily Maintenance, 6C-2

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page Index-3

Periodic Maintenance, 6C-2 Drain Valve, Lavatory, 17-8

Silicate/Phosphate Dropout, 6C-6 Drilling Caution, Intro-2
Water, 6C-4
Drip Moldings, 3A-2, 3A-11
Coolant Level Sensor, 8A1-10, 8C-5 Drive Axle, 2A-1
Coolant Temperature Sensor, 8A1-10, 8C-4 Adjustment, Differential Bearing Preload, 2A-27
Adjustment, Pinion Bearing Preload, 2A-17
Cooling Coil, Air System, 4A-2
Adjustment, Pinion Cage Shim Pack, 2A-20
Cooling System Components, 6B-1 Assembly, Differential and Ring Gear, 2A-23
Coolant Filter Assembly, 6B-2 Assembly, Drive Pinion, Bearing Cage, Shim Pack,
Draining (System), 6B-3 2A-21
Engine Water Pump, 6B-2 Components, 2A-2
Filling (System), 6B-4 Disassembly, Differential and Ring Gear, 2A-7
Hoses and Clamps, 6B-5 Disassembly, Drive Pinion, Bearing Cage, 2A-10
Pressure Testing, 6B-4 Fasteners, 2A-13
Specifications, 6B-8 General Description, 2A-2
Surge Tank Assembly, 6B-2 Inspection, Drive Axle, 2A-3
Thermostat and Housing, 6B-2 Inspection, Matched Ring Gear, Drive Pinion, 2A-15
Installation, Differential Carrier, 2A-33
Corrosion Prevention, 3A-4 Installation, Differential Gear Set, 2A-26
Cruise Control, 9D-1 Installation, Thrust Screw, 2A-33
Operation, 9D-3 Lubrication, 2A-2
System Raod Test, 9D-4 Parts Cleaning and Inspection, 2A-12
Troubleshooting, 9D-5 Removal, Carrier Assembly, 2A-3
Removal, Differential and Ring Gear, 2A-6
Customer Service Removal, Drive Axle, 2A-3
MCI Customer Support Center, Intro-1 Removal, Drive Pinion and Bearing Cage, 2A-9
MCI Service Department, Intro-1 Specifications, 2A-39
CVSA Readjustment Limit, 4E-4 Torque Chart, 2A-36
Driver’s Seat, Operation, 3B-2
Driver’s Window, 3D-2
D Driveshaft, 14-1
Inspection, 14-4
Decals, Exterior, 3A-9 Lubrication, 14-3
Delco Remy 50 MT, (see Starter Motor), 7C-1 Maintenance, 14-3, 14-4
Slip Joint, 14-3
Destination Sign, 3B-2, 3B-5
Specifications, 14-5
Disassembly, 3B-6
Torque Chart, 14-5
Reassembly, 3B-7 U Joint Maintenance, 14-4
Sign Installation, 3B-7 Universal Joint, 14-3
Detroit Diesel, (see Engine), 8A1-1 Drop Tube, Lavatory, 17-4
Diesel Fuel Additives, 9A-5 Drum Brakes, 4E-17
Dispensers, Lavatory, 17-2 Brake Burnishing, 4E-25
Brake Function Test, 4E-25
Dome Light, Lavatory, 17-2 Cleaning and Parts Inspection, 4E-21
Door, 3C-1 Installation, 4E-22
Baggage Compartment, 3C-10 Lubrication, 4E-25
Entrance, 3C-3 Maintenance Schedule, 4E-18
Control Dump Valve, 4A-5 Relining, 4E-23
Control Module, 4A-5 Removal, 4E-18
Service Compartment, 3C-10 Specifications, 4E-28
Torque Chart, 4E-26
Door Spring, Lavatory, 17-2
Dry Break System, 9A-3, 9A-12
Double Check Valve, 4D-12 Filler Neck Adapter, 9A-13

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page Index-4

Level Control Valve, 9A-12 Engine, Caterpillar, 8A2-1

Pressure Relief Valve, 9A-12 Electronic Engine control systems, 8A2-6
Engine Assembly, 8A2-2
Dryer, Air System, 4C-2
Lubrication --- Oil Change Intervals, 8A2-3
Dump Valve, Lavatory, 17-7 Maintenance
Engine Diagnostics, 8A2-9
Inspection & Tests, 8A2-4
E Torque Specifications, 8A2-13
Troubleshooting
Diagnostic codes, 8A2-11
E---15R Brake Valve, 4D-3 Diagnostic Tools, 8A2-10
ECM, 8A1-7, 8C-2 Mechanical Checks, 8A2-9, 8A2-10
Sensor/ECM Replacement, 8A2-10
Electrical Systems, 7A-1
Alternators, 7A-6 Engine, Detroit Diesel, 8A1-1
Batteries, 7A-6 Inspection Intervals, 8A1-4
Circuit Test Equipment, 7A-6 Installation, 8A1-4
Front Junction Box, 7A-4 Lubrication, 8A1-4
Fuse Box, 7A-6 Mounting, 8A1-5
Maintenance, 7A-6 Removal, 8A1-3
Remote Engine Control Box, 7A-4 Specifications, 8A1-23
Troubleshooting Procedures, 7A-7 Torque Chart, 8A1-6
Entrance Door, 3C-3
Electrical Systems (See Multiplex System), 7G-1 Adjustment, 3C-4
Electronic Engine Control Systems, 8A1-7, 8C-1 Components, 3C-3
Air Temperature Sensor (ATS), 8A1-10, 8C-5 Door Actuating Cylinder, 3C-7
Coolant Level Sensor (CLS), 8A1-10, 8C-5 Door Locking Cylinders, 3C-6
Coolant Overtemperature Protection , 8A1-11, 8C-6 Lock Control Valve, 3C-5
Coolant Temperature Sensor (CTS), 8A1-10, 8C-4 Lubrication, 3C-5
Diagnostics, 8A1-11, 8C-6 Manual Air Dump, 3C-5
Electronic Control Module (ECM), 8A1-7, 8C-2 Operation, 3C-3
Electronic Unit Injectors (EUI), 8A1-8, 8C-2 Quick Exhaust Valve, 3C-8
Oil Pressure Sensor (OPS), 8A1-9, 8C-4 Seal Replacement, 3C-9
Oil Temperature Sensor (OTS), 8A1-9, 8C-4 Specifications, 3C-13
System Self Diagnostics, 8A1-11, 8C-6 Equalizer, Battery, 7E-7
Throttle Position Sensor (TPS), 8A1-9, 8C-4 Exterior
Troubleshooting, 8A1-11, 8C-6 Cleaning, 3A-3
Turbocharged Boost Sensor (TBS), 8A1-9, 8C-4 Coatings, 3A-2
Vehicle Interface Module (VIM), 8A1-7, 8C-2 Components, 3A-1
Vehicle Speed Sensor (VSS), 8A1-7, 8C-2 Mirrors, 3A-3, 3A-9
Emergency Buzzer, Lavatory, 17-3 Panels, 3A-2, 3A-6
Vinyl Graphics, 3A-4
Emergency Escape Hatches, 3C-12
Adjustment, 3C-12 Exterior Components, 3A-1
Installation, 3C-12 Bumpers, 3A-3, 3A-11
Maintenance, 3C-12 Cleaning, 3A-3
Removal, 3C-12 Decal Application, 3A-9
Drip Moldings, 3A-2, 3A-11
Emergency Release Valve, 4A-4 Fenders, 3A-3, 3A-11
Engine Fiberglass Repairs, 3A-6
Starting Mirrors, 3A-3, 3A-9
Mud Flaps, 3A-3, 3A-11
Block Heater, 8B-1
Paint, 3A-8
Cold Weather, 8B-1
Panels, 3A-2, 3A-6
Water Pump, 6B-2
Rub Rails, 3A-2
Engine Crankcase Oil, 10-5 Service Tools, 3A-12

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page Index-5

Specifications, 3A-14 Fuel Filter, 9A-10

Structural Welding, 3A-6 Fuel Pro, 9A-9
Fuel System, 9A-1
F Diesel Fuel, 9A-4
Diesel Fuel Additives, 9A-5
Fan Assembly, 6A-3 Dry Break System, 9A-3, 9A-12, 9A-13
Fuel Contamination, 9A-5
Fan Drive Belt Adjustments, 6A-4 Fuel Filter, 9A-10
Fenders, 3A-3, 3A-11 Fuel Flow Check, 9A-7
Fuel Pro, 9A-9
Fiberglass, Repair, 3A-6 Fuel System Priming, 9A-7
Filter, Coolant Filter Assembly, 6B-2 Fuel Tank Removal, 9A-10
Filter Maintenance Schedule, 10-8 Fueling, 9A-3
Specifications, 9A-14
Floor, 3B-2 Troubleshooting, 9A-14
Flush Toilet Pump, Lavatory, 17-2 Fuel Tank, 9A-10
Frame, 3A-2 Fuse Box, 7A-6
Fresh Water Storage Tank, Lavatory, 17-2, 17-4
Front Axle, 1-1
Adjustment, Pressure Relief, 1-21
G
Adjustment, Steering Stop, 1-21 Glass/Glazing, 3D-1
Adjustment, Wheel Bearings, 1-20 Removal, 3D-2
General Description, 1-3 Service Tools, 3D-6
Inspection, Cleaning and Parts Inspection, 1-11 Windows, 3D-2
Inspection, King Pin Bushings, 1-4 Windshields, 3D-2
Inspection, Routine, 1-4
Inspection, Steering Knuckle End Play, 1-4 Governor, 4B-1, 4B-13
Inspection, Tie Rod, 1-6 Adjustment, 4B-14
Inspection, Wheel Bearings, 1-13 Air System Overview, 4A-2
Installation, Knuckle, 1-16 Assembly and Installation, 4B-16
Installation, Knuckle Bushing Seal, 1-15 Inspection, 4B-14
Installation, Steering Knuckle Bushing, 1-14 Operation, 4B-13
Installation, Tie Rod and Tie Rod End, 1-19 Removal and Disassembly, 4B-15
Installation, Tie Rod Arm, 1-19 Specifications, 4B-18
Lubrication, 1-7 Torque Specifications, 4B-17
Removal, Knuckle, 1-8 Graphics, Exterior, 3A-4
Removal, Tie Rod, 1-8 Gross Vehicle Weight Ratings, 15C-4
Service Tools, 1-24
Specifications, 1-25
Torque Chart, 1-23
Troubleshooting, 1-22
H
Front Axle Suspension, Maintenance, 12B-6 Haldex, (see Slack Adjusters, Haldex), 4E-9
Air Springs, 12B-8 Headlight Assemblies, 7F-2
Radius Rods, V ---Link and Bushings, 12B-6 Aiming, 7F-3
Shock Installation, 12B-12 Lamp Replacement, 7F-2
Shock Removal, 12B-12
Sway Bar (As of 60947), 12B-10 Heating and Air Conditioning, 16A-1
Air Filters, 16A-25
Front Junction Box, 7A-4 Components, 16A-4
Front Turn Signal, 7F-3 Compressor, 16A-38
Condenser, 16A-32
Front, Drive and Tax Axle Suspension, 12B-1 Driver Control Box, 16A-36
Fuel Contamination, 9A-5 Driver Evaporator, 16A-36

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page Index-6

Driver’s Display, 16A-18

Duct Cleaning, 16A-37
J
Electronic Sensors, 16A-42 Junction Block, 4A-5
Main Control Box, 16A-15
Main Evaporators, 16A-34 Junction Box
Front, 7A-4
Maintenance Schedule, 16A-24
Rear, 7A-4
Manifold Gauges, 16A-25
Operating Instructions, 16A-20
Parcel Rack Evaporators, 16A-35
Passenger Ram Air, 16A-37 L
Pre---Trip Inspection, 16A-20 Lavatory, 17-1
Pump Down and Charging, 16A-26 Auxiliary Retention Tank, 17-7
Specifications, 16A-52 Dome Light, 17-2
Suction and Discharge Service Valves, 16A-24 Door Spring, 17-2
System Checks, 16A-28 Drop Tube, 17-4
Temperature Pressure Chart, 16A-44 Emergency Buzzer, 17-3
Troubleshooting, 16A-45 Flush Pump, 17-2, 17-4
Horn Fresh Water Storage Tank, 17-2, 17-4
Air, 4D-14, 7D-2 Maintenance, 17-4
Electric, 7D-2 Occupied Sign, 17-3
Operation, 17-3
Hoses, 10-2 Primary Retention Tank, 17-6
Retention Tanks, 17-2
Hoses and Clamps, 6B-5
Secondary Retention Tank, 17-7
Hubs, 15B-1 Service Panels, 17-2
Components, 15B-2 Slide Valve, 17-7
Inspection, 15B-3 Soap Dispenser, 17-2, 17-4
Lubrication, 15B-2 Specifications, 17-10
Wheel Bearings, 15B-5 Thermal Drain Valve, 17-8
Wheel Seals, 15B-6 Toilet, 17-4
Toilet Flush, 17-3
HVAC (see Heating and Air Conditioning), 16A-1 Towel and Tissue Dispensers, 17-2
Troubleshooting, 17-10
Ventilation System, 17-3
I Winterizing, 17-6, 17-7
Lift, Wheelchair, 22A-1
Inflation Chart, Tires, 15C-4 Lifting and Towing, 3E-1, 3F-1
Air Connections, 3F-5
Inspection Schedule, 10-8
General Description, 3E-2, 3F-2
Instrument Panels, Switches, 7F-4 Jacking Points, 3E-3
Lifted Tow Procedure, 3F-4
Interior Components, 3B-1
Non Lifted Tow Procedure, 3F-2
Destination Sign, 3B-2, 3B-5
Driver’s Seat, 3B-2 Light, Lavatory Dome, 17-2
Floor, 3B-2, 3B-4 Light Bulb Data and Specifications, 7F-1
Interior Panels, 3B-2 Front Turn Signal, 7F-3
Parcel Racks, 3B-2 Headlight Assemblies, 7F-2
Passenger Seats, 3B-2 Parcel Rack Lights, 7F-4
Routine Cleaning, 3B-4 Taillight Assemblies, 7F-3
Service Tools, 3B-8 Low Air Pressure Switch, 4A-5, 4D-13
Specifications, 3B-8
Lubricating Oils and Grease, 10-3
Introduction, Intro-1
Lubrication, 10-1
IPX Controller, 11B-3 Capacity Schedule, 10-8

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page Index-7

Dipsticks, 10-2 Solid State Multiplex Module (SMM) Description,

Fill Tubes, 10-2 7G-8
Filter Maintenance Schedule, 10-8 MUX Plug Location Chart, 7G-27
Filters, 10-2, 10-6 Solid State Relay Module (SRM) Function, Input /
Hoses, 10-2, 10-4 Output LED Checklist, 7G-25
Inspection Schedule, 10-8
Lubricating Oils & Grease, 10-3
Lubrication Schedule, 10-9 O
Power Steering Reservoir, 10-2
Preventive Maintenance Schedule, 10-13 Oil Pressure Sensor, 8A1-9, 8C-4
Service Intervals, 10-5 Oil Separator (PuraGuard), 4C-1, 4C-11
Specifications, 10-18 Air System Overview, 4A-2
Lubrication Schedule, 10-9 Filter Element Replacement, 4C-12
Maintenance, 4C-11
Maintenance Kits, 4C-12
Operation and Leakage Test, 4C-11
M Removal, 4C-12
Specifications, 4C-14
Maintenance Schedule Troubleshooting, 4C-13
Body, 10-13
Brakes & Air System, 10-14 Oil Temperature Sensor, 8A1-9, 8C-4
Cooling System, 10-14
Drive and Tag Axles, 10-13
Driveshaft, 10-16 P
Electrical System, 10-14
Engine, 10-15 Paint
Front Axle, 10-13 Application, 3A-8
Fuel System, 10-15 Components, 3A-8
Heating and A/C, 10-17 Surface Preparation, 3A-7
Hubs, 10-16 Panels, 3A-2, 3A-6, 3B-2
Steering, 10-15 Parcel Rack Lights, 7F-4
Suspension, 10-15
Tires, 10-16 Parcel Racks, 3B-2
Transmission, 10-16 Park Brake Relay Valve, 4A-4
Wheels, 10-16
Park Brake Valve, 4A-4, 4D-2
Manifold, Air System, 4A-3 Passenger Window Blinds, 3D-5
MCI Customer Support Center/Service Department, Pedal, Accelerator, 9B-1
Intro-1
Power Steering Lines, 11A-3
Meritor, (see Slack Adjusters, Meritor), 4E-13
Power Steering Pump, 11C-1
MGM (see Brake Chamber or Spring Brake), 4E-2 Maintenance, 11C-1
Mirrors, Exterior , 3A-3, 3A-9 Specifications, 11C-3
Moldings, Drip, 3A-2, 3A-11 Power Steering Reservoir, 10-2

Motor, Starter, 7C-1 PP---1 Park Valve, 4D-2

Pressure Protection Valve, 4A-2, 4D-11
Mud, Flaps, 3A-3, 3A-11
Pressure Regulator, 4D-12
Multiplex System (Electrical Systems), 7G-1
Diagnostic Tool, 7G-23 Pressure Transducers, 4A-6, 4D-13
General Description Preventive Mainteance Schedule, 10-13
Diagnostic Tool Description, 7G-22
Ladder Logic Definition, 7G-17 Primary Retention Tank, Maintenance, 17-6
PDM Hardware, 7G-2 Proheat, 16B-1
PDM Module, 7G-2 Components, 16B-4

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page Index-8

Diagnostics, Component Fault, 16B-24 Relay Valve

Diagnostics, Function and Component, 16B-11 Park Brake, 4A-4
Diagnostics, Mechanical Component Fault, 16B-35 Service Brake, 4A-3, 4D-8
General Description, 16B-3 Spring Brake, 4D-6
Maintenance, 16B-13 Reservoirs, 4D-11
Operation, 16B-11 Emergency Release, 4A-3
Removal, 16B-13 Service Brake, Primary, 4A-2
Service Tools, 16B-41 Service Brake, Secondary, 4A-2
Specifications, 16B-43 Supply, 4A-2
Troubleshooting, 16B-17 Suspension/Accessory, 4A-3
Puraguard Oil Separator/Filter, 4C-1, 4C-11 Rockwell, (see Slack Adjusters, Meritor), 4E-13
Air System Overview, 4A-2
Rub Rails, 3A-2
Filter Element Replacement, 4C-12
Maintenance, 4C-11
Maintenance Kits, 4C-12
Operation and Leakage Test, 4C-11 S
Removal, 4C-12
Schematics, Air System, 4F-1
Troubleshooting, 4C-13
Seats
Pushrod, Brake Chamber, 4E-4 Driver’s, 3B-2
Pushrod Stroke Readjustment Limit, 4E-4 Passenger, 3B-2
Service Brake Chamber, (see Brake Chamber), 4E-2,
4E-6
Q Service Brake Relay Valve, 4A-3, 4D-8
Q Plus Brakes, (see Drum Brakes), 4E-17 Service Brake Valve, 4A-3
Quick Release Valve, 4A-3, 4D-5 Service Compartment Door, 3C-10
Service Panels, Lavatory, 17-2
Shock Absorber, 12B-11
R Side Sash, 3D-2
Radiator & Charge-Air Module, 6A-1 Sign, Lavatory Occupied, 17-3
Air Controls, 6A-3, 6A-7 Sign Curtain Repair, 3B-5
Air Cooler Assembly, 6A-2
Charge-Air Cooler Assembly, 6A-7 Slack Adjusters, Haldex, 4E-9
Clutch Fan Assembly, 6A-3 Adjustment, 4E-12
Engine-To-Fan Belt Installation, 6A-4 Inspection, 4E-10
Engine-To-Fan Belt Removal, 6A-4 Installation, 4E-11
Fan Drive Belt Adjustments, 6A-4 Lubrication, 4E-12
General Description, 6A-2 Removal, 4E-10
Lubrication, 6A-5 Specifications, 4E-28
Maintenance, 6A-4 Slack Adjusters, Meritor, 4E-13
Radiator Assembly, 6A-2, 6A-12 Adjustment, 4E-16
Specifications, 6A-13 Inspection, 4E-14
Radius Rod and V ---Link Installation, Front Axle Inspection, Clevis Position, 4E-14
Suspension, 12B-7 Installation, 4E-15
Lubrication, 4E-16
Radius Rods and V ---Link Maintenance, Front Axle Removal, 4E-15
Suspension, 12B-6 Specifications, 4E-28
Rails, Rub, 3A-2 Slide Valve, Lavatory, 17-7
RD ---3 Emergency Release Valve, 4A-4 Soap Dispenser, Lavatory, 17-2, 17-4
Rear Junction Box, 7A-4 Speed Sensor, 8A1-7, 8C-2

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page Index-9

Spring, Lavatory Door, 17-2 Torque Chart, 11A-11

Spring Brake, 4E-2, 4E-7 Troubleshooting, 11A-7
Caging, 4E-7 Steering Wheel and Column, 11B-1
Components, 4E-3 Column Installation, 11B-4
Disposal, 4E-8 Column Removal, 11B-4
Inspection, 4E-5 Lubrication, 11B-4
Installation, 4E-7 Specifications, 11B-8
Operation and Pushrod Travel Inspection, 4E-4 Tilt/Telescoping Steering Columns, 11B-3
Pushrod Stroke Alert, 4E-3 Torque Chart, 11B-7
Removal, 4E-7 Stewart & Stevenson Wheelchair Lift, 22A-1
Specifications, 4E-28
Uncaging, 4E-7 Stop Lamp Switches, 4A-6

Spring Brake Control Valve, 4A-4 Structural Welding, 3A-6

Spring Brake Relay Valve, 4A-4, 4D-6 Structure, 3A-1

Surge Tank Assembly, 6B-2
SR---1 Spring Brake Control Valve, 4A-4
Suspension, 12B-1
Starter Motor, 7C-1
Specifications, 12B-17
Armature (Testing), 7C-4
Brushes, 7C-4 Suspension Control Systems, 12A-1
Bushing Replacement, 7C-6 Height & Leveling Control System, 12A-3
Disassembly, 7C-4 Height/Leveling Control System, 12A-2
Field Coil Test, 7C-5 Kneeling System, 12A-2, 12A-3
Installation, 7C-7 Leveling Valve, 12A-4
Lubrication, 7C-2 Pressure Protection System, 12A-2
Pinion Clearance, 7C-7 Pressure Protection Valve, 12A-7
Removal, 7C-2 Quick Recovery Valve, 12A-6
Solenoid Test, 7C-5 Rear Rise System, 12A-2
Specifications, 7C-8 Relay Valve R-12, 12A-8
Tests, 7C-3 Suspension Air Filter, 12A-8
Troubleshooting, 7C-2 Suspension Filter System, 12A-2
Tag Unloading System (Electric), 12A-2, 12A-3
Steering Column, 11B-1 Tag Unloading System (Manual), 12A-2, 12A-3
Column Installation, 11B-4 Unloading Valves (Electric), 12A-5
Column Removal, 11B-4 Unloading Valves (Manual), 12A-5
Controller, 11B-3
Lubrication, 11B-4 Sway Bar Maintenance, Front Axle Suspension,
Specifications, 11B-8 12B-10
Tilt/Telescoping Steering Column, 11B-3 Switch
Torque Chart, 11B-7 Instrument Panel LEDs, 7F-4
Troubleshooting, 11B-6 Low Air Pressure, 4A-5
Steering Gear TAS-85 Series, Removal, 11D-4 Main Battery Disconnect, 7E-2
Stop Lamp, 4A-6
Steering System, 11A-1
Bleeding System, 11A-5, 11A-6
Filling Power Steering System, 11A-4
Filters and Reservoirs, 11A-4
T
Fluid Reservoir, 11A-2 Tag Axle, 1-1, 2B-1
Maintenance, 11A-3
Taillight Assemblies, 7F-3
Power Steering Lines, 11A-3
Relay Arm, 11A-3 Tank, Fresh Water Storage, Lavatory, 17-2
Specifications, 11A-11 Tanks, Lavatory Retention, 17-2
Steering Gear, 11A-2
Steering Linkage, 11A-2, 11A-3 Thermal Drain Valve, Lavatory, 17-8
Steering Wheel, 11A-2 Thermostat, 6B-2

MOTOR COACH INDUSTRIES

Printed in Canada.
 Date March 2003 Page Index-10

Throttle Position Sensor, 8A1-9, 8C-4

W
Tilt/Telescoping Steering Column, 11B-3
Waste Retention Tank, Maintenance, 17-6
Tire Inflation Chart, 15C-4
Waste Retention Tanks, Lavatory, 17-2
Tires, 15C-1
Welding
Gross Vehicle Weight Ratings, 15C-4
Caution and Procedure, Intro-2, 7A-2, 8A1-13, 8C-8
Inflation, 15C-2
Drive Axle Procedure, 2A-14
Maintenance, 15C-2
Structural, 3A-6
Replacement, 15C-2
Rotation, 15C-2 Wheelchair Lift, 22A-1
Safety Precautions, 15C-2 Components, 22A-2
Maintenance, 22A-3
Toilet, 17-4 Operation, 22A-3
Toilet, Flush, 17-3 Specifications, 22A-5
Torque Chart, 22A-4
Towel and Tissue Dispensers, Lavatory, 17-2
Wheels, 15A-1
Towing, 3F-1 Maintenance, 15A-2
Lifted Procedure, 3F-4 Periodic Inspection, 15A-2
Non Lifted Procedure, 3F-2 Torque Chart, 15A-4
Towing Air Provisions, 4A-6, 4A-7 Wheel Attachment, 15A-2
Wheel Removal, 15A-3
Transmission (see Automatic Transmission), 13A1-1
Windows, 3D-1, 3D-2
Turn Signal, 7F-3 Driver’s Window, 3D-2
Glass Replacement, 3D-2
Two Way Check Valve, 4A-4
Service Tools, 3D-6
Side Sash, 3D-2
Windshields, 3D-2
U Windshield Washers
Removal, 3D-4
U Joint, Maintenance, 14-4 Service Tools, 3D-6
Troubleshooting, 3D-4
Windshield Wipers, 3D-3
V Winterizing, Lavatory, 17-6, 17-7
Wipers, 3D-3
Valves, (see Air Control Components), 4A-1, 4D-1
Vehicle Interface Module (VIM), 8A1-7, 8C-2
Vehicle Speed Sensor, 8A1-7, 8C-2 Z
VIP Controller (see IPX), 11B-3 ZF As---Tronics (See Automatic Transmission), 13A2-1

MOTOR COACH INDUSTRIES

Printed in Canada.