Starters & Alternators

Technical Manual

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DENSO Starters & Alternators
Table of Contents

DENSO in Europe
> The Aftermarket Originals 04

Introduction
> About This Publication 04
> Product Range 05

PART 1 – DENSO Starters PART 2 – DENSO Alternators

Characteristics Characteristics
> System outline 08 > System outline 42
> How Starters work 09 > How Alternators work 43

Types Types
> Pinion Shift Type 11 > Conventional Type 45
> Reduction Type 14 > Type III 46
> Planetary Type 17 > SC Type 47

Wall Chart 21 Wall Chart 53

Stop & Start Technology 22 Replacement Guide 54

Replacement Guide 28 Troubleshooting

> Diagnostic Chart 55
Troubleshooting > Inspection 56
> Diagnostic Chart 29 > Q&A 58
> Inspection 30
> Q&A 37

Edition: 1, date of publication: August 2016 All rights reserved by DENSO EUROPE B.V. This document may not be reproduced or copied,
Edition: 2, date of publication: October 2016 in whole or in part, without the written permission of the publisher. DENSO EUROPE B.V. reserves
Editorial dept, staff: DNEU AMIS Technical Service, K. Aya the right to make changes without prior notice.
 DENSO in Europe
DENSO in Europe

> The Aftermarket Originals

DENSO Aftermarket Europe is part of DENSO Corporation, In fact, you’ll find original DENSO parts in nine out of ten cars on
one of the world’s top 3 manufacturers of advanced automotive the road. We are also proud to bring that unique expertise to the
technology, systems and components. European independent aftermarket. Our technologically advanced
programmes feature only OE specification products specially
Founded in 1949 DENSO is a pioneer of quality products for the
selected for distributor and end-user customers. We manage that
> The Aftermarket Originals

automotive industry, supplying a huge range of original equipment

supply directly through DENSO Aftermarket Europe, supported
to every major vehicle manufacturer in the world.
by a growing network of local aftermarket sales offices.
Introduction
> About This Publication

Introduction
> About This Publication

This Starters & Alternators Manual from DENSO Aftermarket Europe rotating units. From system data to case studies and visuals
aims to provide distributors, wholesalers and end-users with showing each type, this handy manual will provide all the technical
everything you need to know about our unique, OE specification information required.

4
Introduction

Introduction
> Product Range

> Product Range

True pioneers of Starter and Alternator technology for modern its stator coil.
cars, motorcycles and commercial vehicles, DENSO has become
DENSO Starters
the world’s largest OE rotating parts manufacturer, with a 20
Since introducing its first commercial automotive Starters in the
percent market share. As a result, our replacement Starters and
early 1960s, DENSO has poured its world-leading engineering
Alternators are the world’s smallest and lightest rotating machines
expertise into developing smaller, lighter units that can maintain
for their output, delivering unrivalled efficiency, wear resistance
the highest possible output. In 2001, for example, DENSO introduced
and powerful performance.
the world’s first Planetary Reduction Segment Conductor Motor (PS)
DENSO Alternators Starter featuring a square conductor in the armature coil.
DENSO has pioneered new alternator designs capable of producing
more electrical power more efficiently, yet in a smaller, lighter
unit. In 2000, for example, DENSO introduced the world’s first SC
(Segment Conductor) alternator using a rectangular conductor for

Key Facts
• Completely new, boxed item (no reman) & no core surcharge • 2000 – World’s first Segment Conductor (SC) alternator
• Starter Range include Pinion Shift Starter (GA type); Reduction • 2001 – World’s first planetary-reduction segment conductor
Starters (R and RA types); Planetary Starters (PS) starter
• (P, PA, PS and PSW types); and Stop-Start System Starters (AE, • 2005 – World’s smallest and lightest high-output SC alternators
TS and PE types) • 2011 – Introduction of DENSO Tandem Solenoid (TS) Starter
• Alternator Range include Conventional, Type III (alternator with • DENSO technologies for stop/start systems
small internal fan) and SC (Segment Conductor) Types
• Maximum efficiency by offering small size & light weight units
while delivering the highest outputs

5
 Get inside
• 100% OE specification
• All ‘new in box’
• Ncore
o re-manufactured units and no
surcharge or returns policy
• Extensive applications
Maximum efficiency
• Market leading list
•

As one of the world’s largest automotive component suppliers, DENSO is a global leader in developing and manufacturing rotating machines.
Our unwavering commitment to outstanding quality, design and innovation mean that our Starters and Alternators are selected as original
equipment by carmakers worldwide – winning many supplier and international quality awards along the way. As well as delivering unique,
OE coverage of Toyota and a wide range of European marques such as Fiat, Opel, PSA, BMW, Ford, Volvo and Land Rover, the programme is
continually being updated and expanding.

www.denso-am.eu
PART 1
DENSO Starters
 DENSO Starters | Characteristics
Starters | Characteristics

> System outline

A starter is a device that initiates engine

operation. Since a vehicle engine cannot
start unaided, an external force is required
to provide rotational speed at or above
a set value. The starter drives a built-in
motor using the vehicle battery as a
power source to create power and start
the engine. Unlike normal DC motors,
the starter is only used for a short time
(rated at 30 seconds). Thus, the starter
> System outline

is designed to be very small despite

producing a large output.

Battery

Starter

Transition to compact and lightweight starter

The starter has progressed along with the automobile into a utilized a high deceleration ratio to create an even more compact
“compact, lightweight, high-performance” device. The 1970s saw and lightweight device. Making further reductions in size and weight,
the introduction of the pinion shift type starter, followed in the 1980s the planetary type starter was developed in the first decade of the
by the development of the reduction type starter that incorporated 21st century, incorporating a planetary gear and ferrite magnets.
a deceleration mechanism. By the 1990s, the reduction type starter

Weight

Pinion Shift Type

(G Type)

Reduction Type
(R Type)

• Deceleration Reduction Type Planetary Type

Mechanism Utilization (RA Type) (PS Type)

• High Deceleration • Planetary Gear

Ratio Utilization and Ferrite Magnet
Utilization

1970 1980 1990 2000 Year

8
DENSO Starters | Characteristics

Starters | Characteristics
> How Starters work

Magnetic Switch
Engine Engagement and

Primary Components
Disengagement Mechanism

The starter primarily consists of an armature,

pinion gear, magnetic switch, drive lever, Drive Lever
and overrunning clutch. Additionally, starter
construction can be broadly divided into the
‘motor section’ and the ‘engine engagement
and disengagement mechanism’.

> How Starters work

Motor Section
Armature
Pinion Gear

Overrunning Clutch

Motor Section Principles of the motor section

Motor principles are explained using Fleming’s Left-Hand
The motor section primarily consists of an armature, Rule*. The size of the electromagnetic force is proportional
field coil and brushes. to the strength of the magnetic field, size of the current, and
length of the conductor.
Brush
Armature
Electromagnetic Force Electromagnetic Force

Magnetic Field Current

Commutator

N S
Magnetic
Field
Current
Brush
*According to Fleming’s Left-Hand Rule, three fingers on the left hand can be used
to represent the following phenomenon; pointer finger: direction of the magnetic
field (North to South), middle finger: direction of current (positive to negative), thumb:
Field Coil direction of electromagnetic force.

Direction of Rotation
Operations of the motor section
For the starter to operate as a motor, the electromagnetic
Field Coil
force must be continuous and work in a fixed direction.
Therefore, the motor is equipped with a commutator and N S
brushes so that current always flows in a fixed direction
to the North pole side or South pole side of the armature.
As a result, the coil generates a force that works in a Armature Coil
fixed direction so that the motor can rotate continuously.
An actual starter combines multiple armature coils with Brush Current
Battery
the commutator. Commutator

9
 DENSO Starters | Characteristics
Starters | Characteristics

> How Starters Work

Engine engagement and disengagement mechanism

The starter rotates the engine by engaging the starter pinion gear with the engine ring gear. If the pinion gear and ring gear remain engaged
after the engine is started, the pinion gear will be rotated by the engine at high speeds, causing starter breakage. Therefore, the pinion gear
must smoothly engage the ring gear only when the starter is operating, and must disengage immediately after the engine has started.

Magnetic Switch
Primary Components
The engine engagement and disengagement
> How Starters work

mechanism primarily consists of the magnetic Drive Lever

switch, pinion gear and drive lever.

Force Rotating the Armature

Armature

Pinion Gear

Ring Gear

Spiral Spline
Force Pushing the Pinion Gear Out

Engagement
When the starter is operated, the armature begins to rotate, and Role of the spiral spline
the drive lever pushes the pinion gear out to engage the ring gear. The spiral spline is engraved into the armature shaft (engraved into
the drive shaft for reduction type, and planetary type starters) to
However, there are instances when the pinion gear and ring gear
push the pinion gear out. Even when the pinion gear only slightly
collide. In such cases, the force pushing the pinion gear out, and
engages the ring gear, the spiral spline allows the pinion gear to
the force rotating the armature work to assuredly engage the two
be pushed out to ensure complete engagement using the force
gears. The effect of the two previously mentioned forces combined
rotating the armature.
with the spiral spline make the pinion gear slip onto the ring gear,
enabling assured gear engagement.

Disengagement
Once the engine has started and the starter has been stopped, the pinion gear is drawn back and disengages from the ring gear.
Simultaneously, the armature stops rotating.

10
DENSO Starters | Types

Starters | Types
> Pinion Shift Type

Outline Construction of the Pinion Shift Type Starter

In the pinion shift type starter, magnetic switch Magnetic Switch

> Pinion Shift Type

force is transmitted via the drive lever to push
the pinion gear (located above the armature
shaft) out and engage the engine ring gear.

As such, the pinion shift type is a system that Drive Lever

transmits force from the motor directly to the
ring gear (G and GA types).

Pinion Gear

Features and benefits

Armature
>>Unique structure with the pinion gear pushed
through the drive lever
>>Spiral brush spring Yoke
>>Aluminium end frame

Overrunning Clutch

Characteristics Armature
The armature generates
Primary components motor rotational power, Armature Coil
Pole Core and consists of a core,
Yoke
armature shaft, armature Armature Shaft
The yoke creates the magnetic field Brush
coil, and commutator.
necessary to rotate the motor, and Commutator
The entire armature coil
consists of field coils, pole cores, and
is secured with resin to
brushes. The field coils are directly Core
improve heat and vibration Spiral Spline
wound around the pole cores and
resistance. In addition, a
secured with resin to improve heat
Field Coil spiral spline is engraved into the armature shaft for connection
resistance and vibration resistance.
to the overrunning clutch.

Outer Spring

Pinion Gear
Overrunning clutch
The overrunning clutch prevents starter damage due to armature overrun* by providing a means to
smoothly separate the pinion gear from the ring gear. The overrunning clutch consists of an inner,
outer, clutch rollers and springs.
Clutch Roller
Inner
(1) When starting the engine (2) A
 fter engine start
When the armature rotates, force is first transmitted to the outer When the ring gear rotates the pinion gear, the rotational speed of
(a component in contact with the the inner is higher than that of the outer. However, since the clutch
armature shaft), followed by the clutch When starting the engine rollers move in a direction such After engine start
rollers, then finally to the inner (a Direction of that the springs are compressed, Clutch Roller
Clutch Roller Spring Outer and Inner
component integrated with the pinion Rotation for the inner and outer are unlocked.
are Unlocked
Spring the Outer
gear). The clutch rollers are pushed by Therefore, the pinion gear rotates
the springs to the narrower side of the idly, and the rotational force of the Inner

indentations in the outer and the gap pinion gear is not transmitted to Outer
in the inner, thereby locking the outer Inner the armature. As such, armature
and inner together. As a result, the Outer overrun is prevented. Pinion Gear
armature torque is transmitted via the Pinion Gear
inner to the pinion gear, causing the Direction of Rotation for the Inner
gear to rotate. Outer and Inner are Locked

*Overrun is when the pinion gear fails to disengage from the ring gear after the engine starts, and the engine rotates the armature at high speed.
11
 DENSO Starters | Types
Starters | Types

> Pinion Shift Type

Return Spring
Characteristics
Magnetic switch
Plunger
> Pinion Shift Type

The magnetic switch serves to push the pinion gear

out, disengages the pinion gear, and turn the motor
power supply ON and OFF. The magnetic switch
Main Contact
primarily consists of a pull-in coil, holding coil, return
spring and plunger. Both the pull-in coil and holding
coil have the same number of copper windings;
Pull-in Coil
however, each coil is wound in the opposite direction.
Magnetic switch operation can be broadly divided
Holding Coil
into “pull-in”, “holding”, and “return”.

Starter Switch
Pull-In Coil Magnetomotive Force
Plunger
Holding Coil
(1) Pull-in Magnetomotive Force
When the starter switch is closed, current flows Main Contacts
Magnetic Switch
through the pull-in coil and the holding coil. The
magnetomotive force from both coils is applied Holding Coil
Battery
to the plunger, overcoming the return spring force.
As a result, the plunger is pulled in, and the main
Pull-In Coil
contacts close.

Field Coil Armature Return Spring

Plunger Starter Switch

Holding Coil
(2) Holding Magnetomotive Force
Main Contacts
When the main contacts close, the pull-in coil is placed Magnetic Switch
in a short circuit condition, thereby stopping the flow Holding Coil
of current through the coil. As a result, the plunger Battery
is pulled in by only the magnetomotive force of the
holding coil, placing the starter in a holding status. Pull-In Coil

Field Coil Armature Return Spring

Plunger Starter Switch

(3) Return
Pull-In Coil
When the starter switch is opened with the main Holding Coil
Magnetomotive Force
Magnetomotive Force
contacts closed, current flows through both the
Return Spring
pull-in coil and the holding coil. Since both coils are Magnetic Switch Expansion
reverse-wound with the same number of copper Holding Coil
windings, the direction of the magnetomotive force for
the pull-in coil becomes the opposite of that during Main Contacts
pull-in. Therefore, the holding coil magnetomotive Pull-In Coil
force cancels out that of the pull-in coil, resulting in the
Battery
plunger returning to the original position due to return
spring expansion, and the main contacts opening. Field Coil Armature Return Spring

12
DENSO Starters | Types

Starters | Types
> Pinion Shift Type

Operation
When Starting the Engine

> Pinion Shift Type

>>When the starter switch closes, the pinion gear is However, when the teeth on the pinion gear and ring gear come
pushed out in the direction of the arrow below by into contact, the pinion gear is pushed forward and collides with the
the drive lever, causing the magnetic switch to apply ring gear without engaging. To ensure that the teeth engage, the
current to the armature. compression strength of the drive spring mitigates the force of the
>>The armature rotates, and pushes the pinion gear out armature spiral spline pushing the pinion gear out. Simultaneously,
via the armature spiral spline. the drive spring acts to displace the position of the pinion gear teeth.
>>The pinion gear then engages the ring gear and starts As a result, the pinion gear engages the ring gear to start the engine.
the engine.

Holding Coil Starter Switch

Force Compressing the Drive Spring
Main Contact
Drive Spring
Return Spring
Drive Lever
Plunger

Main Contact
Overrunning Clutch

Pinion Gear

Force Pushing the

Pinion Gear Out Pull-In Coil

Ring Gear Armature

Holding Coil Starter Switch

Drive Spring Main Contact
Engine Start Return Spring
>>When the magnetic switch applies current to Drive Lever

the armature, the drive lever holds the drive spring Plunger
Overrunning Clutch
in place.
Main Contact
>>To prevent armature overrun when the ring gear
rotates the pinion gear, the overrunning clutch
operates such that the pinion gear rotates idly.
Pinion Gear

Ring Gear Armature Pull-In Coil

Holding Coil Force of the Return Spring Starter Switch

After Engine Start Main Contact

Drive Spring
Return Spring
>>When the starter switch opens, the magnetic
Drive Lever
switch is no longer held, and the plunger returns
to the original position due to the return spring, Plunger
Overrunning Clutch
causing the main contacts to open. Main Contact
>>As a result, the armature stops rotating, and the
drive lever separates the pinion gear from the ring
gear to stop the starter. Pinion Gear

Ring Gear Pull-In Coil

Armature

13
 DENSO Starters | Types
Starters | Types

> Reduction Type

Outline RA Starter features and benefits

> Reduction Type

>>The reduction type starter (R and RA type for example) uses a >>High-speed motor with an improved deceleration ratio and
deceleration mechanism. a heat-resistant electric wire reduces the size and weight of
>>In the pinion shift type starter, since motor power is the motor.
transmitted directly to the ring gear, motor size is proportional >>Improved anti-dust and waterproof capabilities.
to starter output, and therefore the motor is very large. >>Minimized friction and wear of the bearings.
>>However, since the reduction type starter uses the
deceleration mechanism, a large output can be generated
from a small motor. As such, the reduction type starter is
more compact and lightweight than a pinion shift type starter.

Construction of the Reduction Type Starter

Armature

Drive Gear

Idle Gear

Pinion Gear

Magnetic Switch
Overrunning Clutch

Ball Bearing

Characteristics Ball Bearing

Primary Components
Armature
>>The armature in the reduction type starter rotates at higher speeds
than in the pinion shift type starter.
>>Ball bearings are used as the armature shaft bearings. Armature Shaft

>>These generate less friction, allowing the armature to rotate smoothly.

Drive Gear
Deceleration mechanism Idle Gear
>>The deceleration mechanism comprises of an armature drive gear, idle gear and clutch gear.
>>The deceleration mechanism reduces speed to between 1/3 and 1/4 of the original value by Pinion Gear
transmitting armature rotational speed in order through the drive, idle, and clutch gears.
>>As a result, the torque transmitted to the pinion gear increases. Clutch Gear

Deceleration mechanism theory

>>The following diagram uses a deceleration mechanism consisting of two gears. Number Rotational Torque
of Teeth Speed Ratio Ratio
>>When gear “A” has 10 teeth, and gear “B” has 30 teeth,
Gear A 10 3 1
gear “B” rotates only once for every three rotations Gear B
Torque: 1 N·m Gear B 30 1 3
of gear “A”.
>>In this situation, if the torque of gear “A” is 1, Gear A

the torque of gear “B” is three times that of gear “A”. Number of Teeth: 10
Number of Teeth: 30
The deceleration mechanism rotates a small gear at
Torque: 3 N·m
high speeds to generate a large torque, enabling a
more compact, and lightweight motor to be used.
14
 DENSO Starters | Types

Starters | Types
> Reduction Type

Overrunning Clutch and Magnetic Switch

> Reduction Type

>>In the pinion shift type starter, where the overrunning clutch and magnetic switch are not arranged coaxially, force from these two
components is transmitted through the drive lever.
>>However, in the reduction type starter, the overrunning clutch and magnetic switch are arranged coaxially.

(1) Overrunning clutch construction (2) Magnetic switch construction

>>The overrunning clutch primarily comprises of the pinion >>The magnetic switch is made up of a holding coil, pull-in
gear, clutch roller, pinion shaft, clutch gear, drive spring, coil, return spring, drive spring and plunger.
and return spring. >>In the magnetic switch starter switch operation causes
>>The rotational force of the armature transmitted to the current to flow to the pull-in coil and holding coil.
overrunning clutch is conveyed in order from the armature >>The resulting magnetic force and spring force cause the
drive gear to the clutch gear via the idle gear, then through plunger to pull-in, hold or return.
the clutch roller and the pinion shaft to the pinion gear.

Pinion Gear Clutch Roller Ball Bearing Holding Coil Drive Spring

Pull-In Coil

Drive Spring

Plunger
Return Spring Clutch Gear Pinion Shaft

Return Spring

Pinion Shift Type Starter Reduction Type Starter

Return Spring Plunger Attraction
(3) Overrunning clutch Drive Spring Plunger Attraction
Plunger Main
and magnetic switch operation Plunger
Contacts
>>Overrunning clutch and magnetic switch Overrunning Clutch
Drive
operations differ between the pinion shift Drive Lever Spring
type starter and reduction type starter. Pinion Gear
>>In the pinion shift type starter, when the Pinion
Main Contacts
starter switch is closed, current flows to the Gear
Overrunning Return Springs
magnetic switch, and the plunger is pulled Clutch Drive Spring
in. Plunger movement is transmitted to the Force Pushing the
Force Pushing the Pinion Gear Out
overrunning clutch via the driver lever that
Pinion Gear Out
connects the two devices, thereby pushing
the pinion gear out.
>>In the reduction type starter, when the starter
switch is closed, current flows to the magnetic
switch. The plunger is pushed out in the
direction of the pinion gear, pushing out the
pinion gear.

15
 DENSO Starters | Types
Starters | Types

> Reduction Type

Operation
When Starting the Engine
> Reduction Type

>>When the pinion gear engages the ring gear, the main However, when the teeth on the pinion gear and ring gear
contacts close, the armature is energised, and the starter come into contact, the pinion gear is pushed forward and
begins to rotate. collides with the ring gear. To ensure that the teeth engage,
>>The rotational speed of the armature is first decreased by the compression strength of the drive spring softens the
the drive gear and idle gear, then transmitted to the pinion force of the pinion shaft spiral spline, pushing the pinion gear
gear, resulting in pinion gear rotation and engine start. out. Simultaneously, the drive spring acts to displace the
position of the pinion gear teeth. As a result, the pinion gear
engages the ring gear to start the engine.

Return Springs
Drive Gear
Idle Gear
Pinion Gear Armature
Force Compressing Plunger
the Drive Spring

Main Contacts
Drive Spring

Starter Switch
Ring Gear
Plunger Attraction

Pinion Shaft Clutch Gear

Return Springs
Drive Gear
Idle Gear
Engine Start Armature
Plunger
>>When the magnetic switch applies current to the
armature, the magnetic switch is held in place. Pinion Gear
>>To prevent armature overrun when the ring gear
rotates the pinion gear, the overrunning clutch
operates such that the pinion gear rotates idly. Main Contacts
Starter
Drive Spring
Switch

Ring Gear Pinion Shaft Clutch Gear

Return Springs
Drive Gear
Idle Gear
After Engine Start Expansion due to the Armature
>>When the starter switch opens, the magnetic switch Return Springs Plunger

is no longer held, and the plunger returns to the Pinion Gear

original position due to return spring expansion,
Drive Spring
causing the main contacts to open.
>>The armature will stop rotating, and the pinion gear Ring Gear Main Contacts
separates from the ring gear to stop the starter. Starter
Expansion due Switch
to the Return
Pinion Shaft Clutch Gear Springs

16
DENSO Starters | Types

Starters | Types
> Planetary Type

Outline Construction of the Planetary Type Starter

Similar to the pinion shift type starter, the

> Planetary Type

planetary type starter (P, PA, PS and PSW
Magnetic Switch
type for example), transmits magnetic switch
force via the drive lever to push the pinion Drive Lever
gear (integrated with the overrunning clutch)
out, and engage the engine ring gear. Motor Armature
rotational power is then transmitted to the ring Pinion Gear
gear. The planetary type starter utilises both a
deceleration mechanism with planetary gears,
and a shock absorber bearing.

The planetary type starter uses planetary

Shock Absorbing Bearing
gears between the overrunning clutch and
armature as a deceleration mechanism. Internal Gear
Much like the reduction type starter, this
system generates a large torque for a small
motor, but is comparatively more compact
and lightweight than a standard pinion shift
type starter. Shock Absorbing Bearing

Additionally, if the starter engages the ring

Overrunning Clutch
gear when the engine is rotating in reverse,
the shock absorber bearing acts to soften
the shock of reverse rotation from the engine
Planetary Gears
side, and protect the internal gear.

PS Starter (PS: Planetary Reduction Segment Conductor Motor)

The PS starter, developed by DENSO in 2001, is 22 percent lighter and 14 percent smaller than the RA starter, resulting in improved fuel
consumption and excellent mountability in the vehicle. DENSO’s technological innovation has allowed a smaller and lighter starter; through
improving the yoke, employing a segment conductor (rectangular conductor) in the armature coil and improving the armature commutator shape.

Features and benefits

>>Small size, light weight, easy mountability and
low cranking noise.
>>Placing a magnet between the yoke main poles
increases the total magnetic flux.
>>Rectangular conductor used with the armature
coil improves the winding density (space factor).
>>Newly developed surface commutator, placed on
the end surface of the armature, reduces the total
length of the armature.
>>The deceleration ratio was increased from 4.4 to
7.9, resulting in further reduced size of the motor.
>>Shock absorber is used to absorb the shock of
the deceleration device caused by the increased
deceleration ratio. The PS starter uses the
planetary gear as the deceleration device.

17
 DENSO Starters | Types
Starters | Types

> Planetary Type

Characteristics
Cantilever Type Center Impeller Type
Primary Components Clutch Clutch
> Planetary Type

Overrunning clutch Front Bearing

Front Bearing
There are two types of clutches
depending on the shape and
the pinion gear position; a center
impeller type and a cantilever type. Pinion Gear Pinion Gear
E045133E E045133E

Deceleration Mechanism
The deceleration mechanism in the planetary type starter consists
of three planetary gears, a sun gear connected to the armature
shaft and an internal gear that surrounds the entire assembly.
The deceleration mechanism reduces speed to between 1/5 and 1/8 of the original value by transmitting armature rotational speed in order
through the sun gear, planetary gears and planetary carrier shaft. The torque is transmitted to the planetary carrier shaft, and then the
pinion gear increases.

Internal Gear
Sun Planetary Carrier Shaft Planetary Gear Sun Gear
Gear

Planetary
Gears

Internal
Armature Shaft Armature
Gear

When the armature rotates, the sun gear attached to the armature shaft also rotates. In turn, the three planetary gears engaging the sun gear
rotate. As a result, the planetary gears move about the sun gear (in the same direction as the sun gear) along the inner circumference of the
fixed internal gear. Since the planetary gears are connected to the planetary carrier shaft, the shaft also rotates when the planetary gears orbit.

Sun Gear Planetary Gear

Direction of Rotation for the
Planetary Carrier Shaft

Internal Gear
Pinion Gear

Armature Shaft

Direction of Rotation for

the Planetary Gear

Planetary Carrier Shaft Direction of Rotation for the Sun Gear

Fixed Internal Gear

Since the internal gear is fixed in place, the deceleration ratio of Equation for Calculating the Deceleration Ratio of the Planetary Type Starter
the planetary type starter deceleration mechanism is determined Deceleration Mechanism

by the number of teeth on the sun gear and the internal gear. Number of Sun Gear Teeth
The deceleration ratio is calculated using the equation below. Deceleration Ratio =
Number of Sun Gear Teeth
+ Number of Internal Gear Teeth
For example, according to the deceleration ratio equation, if the
Ex. Number of sun gear teeth: 11
sun gear has 11 teeth and the internal gear has 45 teeth, the
Number of internal gear teeth: 45
armature rotational speed is reduced to 1/5 of the original value.
Deceleration Ratio = 11 = 11 = 11 .= 1
.
11+45 56 5.090 5

18
 DENSO Starters | Types

Starters | Types
> Planetary Type

Shock Absorber Bearing

When the shock of reverse rotation from the engine side is added to the internal gear, the shock absorber bearing performs the following
functions: 1) mitigation of a portion of the shock, 2) suppression of the shock placed on the sun gear and internal gear to below a set
value, and 3) protection of the internal gear from damage and deformation.

> Planetary Type

Construction of the Shock Absorber Bearing
(1) Shock absorber bearing construction
Internal Gear
The shock absorber bearing consists of a centre Wave Washer
bearing case, two clutch plates and a spring washer. Centre Bearing Case
The shock absorber bearing and internal gear are Spring Washer Centre Bearing Case

connected by a wave washer sandwiched between

Spring Washer
the two components.

(2) Shock absorber bearing operation

Clutch plate 1 inside the shock absorber bearing Clutch Plate 2
Clutch Plate 1 Clutch Plate 2
connects with the internal gear. Spring washer
force pushes clutch plate 2 against clutch plate 1 to Clutch Plate 1

generate frictional force, thereby keeping the clutch Clutch Plate 2

plates still. When a shock from reverse rotation of Clutch Plate 1 N
Equation Representing Frictional Force
the engine is added to the shock absorber bearing, f = µN
f
and the force of the shock exceeds the clutch plate f: Frictional force
µ: Static friction coefficient
frictional force, clutch plate 1 rotates and mitigates a N: Force of the spring washer holding down
portion of the shock. As a result, the shock placed on clutch plate 2
F F: Shock of reverse rotation from the engine side
the internal gear is suppressed below a set value.

Clutch Plate 1
f > F: No clutch plate movement Ú Shock absorber bearing remains still.
f < F: Clutch plate movement Ú Shock absorber bearing mitigates a portion of the shock.

Yoke Yoke Using Ferrite Magnets

A portion of P and PA type starters use field coils in the yoke. In
addition, some PA type starters, as well as PS and PSW type starters,
use ferrite magnets. Yokes that use the ferrite magnets achieve the
same quantity of magnetic flux as yokes that use field coils, yet have a
shorter motor shaft length and more compact motor.

Armature
P and PA type starters use coated electrical wires with circular P and PA type starters use a cylindrical commutator. However,
cross sections for the armature coil. However, PS and PSW type PS and PSW type starters use uncoated angular electrical wires as
starters use uncoated angular electrical wires. As a result, the the commutator; creating the commutator surface from the end of
space factor* in PS and PSW type starters is improved and torque the armature. As a result, armature shaft length is shorter, and the
is increased due to less coil resistance and heat generation. armature itself is more compact.
*Space factor: A ratio of the cross-sectional area of coated electrical wires
(or uncoated electrical wires) to the cross-sectional area of the coil.
Ends of the Armature Coil
Compact Armature Used as the Commutator
Cylindrical
P, PA Types Commutator
Armatuer Coil Cross Section
Armature Core Armature Core Commutator Surface
The space factor is increased by
Winding Enclosure using uncoated angular electrical Winding Enclosure
wires with the same diameter as the
coated electrical wires.

PS, PSW Types

Coated Electrical Wires

Uncoated Electrical Wires View A

P, PA Type Starters PS, PSW Types
(Coated Electrical Wires) (Uncoated Angular Electrical Wires) Reduction in Armature View A
Shaft Length

19
 DENSO Starters | Types
Starters | Types

> Planetary Type

Operation
Similar to the pinion shift type starter operation, in the planetary type starter, magnetic switch force is transmitted via the drive lever to
> Planetary Type

push the pinion gear (integrated with the overrunning clutch) out and engage the engine ring gear. As a result, motor rotational force is
transmitted to the ring gear.

In the pinion shift type starter, armature rotational power is transmitted directly to the ring gear. In the planetary type start, however,
armature rotational power is transmitted to the pinion gear after the rotational speed of the armature is decelerated by the sun gear,
planetary gear, and internal gear.

Pinion Shift Type Starter

Magnetic Switch

Drive Lever

Overrunning Clutch

Pinion Gear

Ring Gear Armature

Planetary Type Starter

Magnetic Switch

Drive Lever

Overrunning Clutch

Pinion Gear

Ring Gear Armature

Deceleration Mechanism
(Sun Gear, Planetary Gears, Internal Gear)

20
 Technical Overview DENSO Starter
Discovering DENSO Technology

R, RA Types Starter GA Type Starter P, PA Types Starter

Brush Spring
Armature Holding & Pull-in Coil Holding & Pull-in Coil
Field Coil Magnetic Switch
Brush Magnetic Switch Armature
Yoke

Drive Gear Field Coil

Brush
Drive Lever Field Coil

Idle Gear Clutch

Clutch
Armature
Yoke Planetary Gear
Magnetic Switch

Holding & Pull-in Coil Internal Gear

Pinion Gear
Pinion Gear Clutch Sun Gear
Pinion Gear

Starter Type Product Outline Feature of the product

R, RA Types The R and RA type starters use a compact high-speed motor
(Reduction Method) that is decelerate by 1/3 to 1/4 to drive the pinion gear.
R Type
In the GA type starter, the force of the magnetic switch (via the
GA Type Weight
drive lever) pushes the pinion gear outwards to engage the RA Type
(Pinion Shift Method) (kg)
engine ring gear.
P, PA Types
The P and PA type starters use the same type of compact GA Type
P, PA Types
high-speed motor as the reduction type, but use a planetary
(Planetary Method)
gear as the deceleration mechanism.

Output (kW)

21
Starters | Wall Chart
 DENSO Starters | Stop & Start Technology
Starters | Stop & Start Technology

> Idling Stop System (ISS)

Outline
The number of vehicles equipped with idling stop system (ISS) is However, the ISS frequently operates the starter, leading to engine
on the rise due to increased public awareness of environmental vibration and noise. To reduce these undesirable effects, a starting
issues, and stricter CO2 exhaust gas regulations. The ISS mechanism was required that could quickly and smoothly start and
automatically stops the engine* when the vehicle is not moving, stop the engine.
and restarts the engine when accelerator depression is detected. *Several conditions must be met to stop the engine. These conditions vary according
Therefore, the amount of engine idle time decreases, and both to the vehicle

the fuel consumption and CO2 exhaust gas quantities are reduced.

Idling Stop System

Automatically stops and restarts the engine.
> Idling Stop System (ISS)

Engine Start Driving Vehicle Stopped Engine Restart

Engine Stopped

Functionally, ISS continues to evolve towards further fuel DENSO has been working on ISS technology since the 1980s.
consumption rate improvements such as vehicles equipped with This experience, paired with our in-depth knowledge of powertrain
expanded idling stop (engine stops during deceleration) and high- and thermal management systems, gives us a unique advantage
output regenerative braking. These improvements point towards to provide car manufacturers with a complete systems approach.
full-scale popularization of idling stop devices. Depending on The company understands how to seamlessly integrate ISS
vehicle manufacturer specifications, the ISS can help improve fuel components into the vehicle and can offer superior technical support
efficiency by approximately 3 to 5 percent. DENSO has developed that comes from decades of integration experience. DENSO can
ISS technology that can improve fuel efficiency over 7 percent also provide car manufacturers with different technology solutions
depending on the vehicle manufacturer’s overall systems approach. depending on their specific needs and requirements.

ISS Key Features

> Compared to vehicles not equipped with ISS, ISS-equipped > When restarting the engine, the battery voltage will decrease
vehicles undergo at least 10 times the number of engine start-ups. due to power from the battery being used to drive the starter. When
Since frequent engine start-ups not only place load on the starting driving the starter, the supply of voltage to electrical equipment
system, but also on the battery due to a constant need for a power may be boosted by a device such as a DC-DC converter.
supply, a more robust starting system and battery are required. > Depending on the vehicle, idling stops may be suspended when
> ISS-equipped vehicles use a charging control system that repeats the number of starter operations reaches a specified value.
battery charging and discharging to improve fuel economy. Since
repeated charging and discharging places a load on the battery,
a high-performance, long-life battery specifically for ISS-equipped
vehicles is required. Using a battery other than the aforementioned
specialized battery may lead to early battery deterioration and
ISS malfunctions.

22
DENSO Starters | Stop & Start Technology

Starters | Stop & Start Technology

> Idling Stop System (ISS)

Example of ISS configuration & its components

Coolant
Temperature CVT Oil
Sensor Temperature Back-Up
Crankshaft Boost Each Applicable Electrical Device
Position Converter
Sensor

Engine

CVT
Ambient Temperature Sensor

Permanently
Alternator Engaged Starter

CVT Combination Meter

Electric

> Idling Stop System (ISS)

LIN Oil Pump

A/C Amplifier

Engine Stop & Start Computer

Power Steering Computer

Battery
Stop & Start System
Current
Cancel Switch
Sensor
Airbag Sensor
Cooler Thermistor
- +
Vacuum Sensor
Battery
Hood Lock Switch
CAN

Engine Control Computer Skid Control Computer Main Body ECU

Accelerator Neutral Stop Light Speed Master Cylinder Right Front Door
Pedal Sensor Start Switch Switch Sensor Pressure Sensor Courtesy Light Switch

Example of Item Example Operating Conditions (Idling stop occurs when

ISS Operating all of the following conditions are satisfied)

Conditions Engine Coolant Temperature After Warm-Up

Driver-Side Door Closed
ISS primarily operates Engine Hood Closed
according to the example Road Surface Gradient Approximately 10° or less
conditions as shown in Vehicle Speed 0 km/h
the table. The operating
Accelerator Pedal Released
conditions differ according
Brake Pedal Pressed
to the car manufacturer
and car model. Shift Position “D” range
Vehicle Speeds History After and engine start-up and when speed is input
Idling Stop Button ON

23
 DENSO Starters | Stop & Start Technology
Starters | Stop & Start Technology

> Idling Stop System (ISS)

DENSO ISS Starters Overview

Advanced Engagement (AE) Starter
The Advanced Engagement (AE) Starter With an AE starter, once the vehicle comes the brushes used for conventional starters,
works like a typical planetary starter but has to a stop, the fuel will be cut and the engine as well as unique structure and pinion
10 times the durability. When it’s energized, will stop. However, the engine must reach spring mechanism (AE mechanism). AE
the pinion shifts forward, engages with the zero rpm to shut down. At any point after mechanism construction features a pinion
flywheel and immediately spins. As a starter the engine is at zero rpm, the starter can gear that is separated from the inner clutch
motor-based solution for ISS, the AE starter be re-energised to restart the engine. The and the addition of a pinion spring. When
is the easiest to integrate with the engine benefits and convenience of the AE Starter the pinion gear collides with the ring gear,
- requiring no unique controls, software or means that it is used by a wide range of pinion spring deflection and the effect of
engine modifications. The AE starter helps manufacturers including Toyota, Hyundai, the spiral spline produce a smooth gear
car manufacturers achieve fuel savings of Honda, Fiat, Volkswagen, Audi, BMW engagement. Since only the force used
approximately 3-5 percent depending on and Mercedes-Benz. to push out the pinion gear is applied to
engine size, and allows easy mountability the edges of the pinion gear and ring gear,
The AE Starter’s key design features include
for the customer, being about the same size wear on the gear tips is suppressed, thereby
> Idling Stop System (ISS)

dual layer, long-life electrical brushes which

as a conventional starter. improving the durability of both gears by 90
have six to ten times durability compared to
percent.

AE Starter Typical Starter

Long Life Solenoid

Long Life Brush

AE Mechanism

Ring Gear Ring Gear

Pinion Clutch Pinion Clutch

Pinion Helical Helical

Spring Spline Spline

Engage by pushing force of solenoid PV (on Ring Gear): 1.6 kPa·m/min Engage by motor torque PV (on Ring Gear): 39 kPa·m/min

Engineering Key Point

Separate pinion from clutch and add pinion spring between pinion and clutch.
Complete meshing before motor rotation by spring compression and helical spline.

Benefit

Reliability Ring Gear wear amount

Durability test results after 300.000 cycles on 2L gasoline engine Pinion

x 10.000 starting cycle

Wear amount
(mm)

Ring Gear
AE Starter Typical Starter AE Starter Typical Starter

24
DENSO Starters | Stop & Start Technology

Starters | Stop & Start Technology

> Idling Stop System (ISS)

“Change of Mind” Starters

Engine restart times are critical for stop TS Starter, which have the capability of starter that allows the engine to restart
and start engines. A unique starting system restarting before the engine reaches zero with no noticeable lag time. DENSO’s PE
is required to restart an engine after fuel rpm. That means it doesn’t need to wait or TS Starter, paired with a high-efficient
supply is cut and before a vehicle comes for the engine to completely drop from idle alternator and battery, and deceleration
to a full stop. DENSO has developed two speed to zero rpm, like the AE starter. This regeneration system can improve fuel
different starters, the PE Starter and the is what we call a “Change of Mind” capable efficiency by more than 7 percent.

Tandem Solenoid (TS) Starter

DENSO’s new starter, Tandem Solenoid gear into the spinning flywheel ring gear.
(TS) starter, shaves up to 1.5 seconds Aside from the dual solenoid design, TS
off the restart time when restarting the Starter is equipped with all the same long-life
engine, compared to the DENSO’s previous features of the AE Starter. Additionally, the
ISS starter. The TS Starter is designed basic construction is identical to a planetary
specifically for ISS. It adopts a co-axial dual starter and it can fit in the same space as
solenoid in the magnetic switch to allow for a conventional starter. The TS Starter has

> Idling Stop System (ISS)

independent control of the starter’s pinion already been launched and adopted by many
gear shifting mechanism, and motor rotation. Asian car manufacturers. Various European
This enables the engine to restart while it is car manufacturers such as Jaguar and
still rotating. Special software is required to Land Rover also use a TS Starter for new
control the timing and synchronize the pinion ISS-equipped vehicle models.

To start the engine, starters shift the pinion gear forward TS Starter
to mesh with the engine ring gear, which transmits the Independent control of pinion gear shift and motor energization by two solenoids
rotational force of the starter motor through the pinion
gear. The conventional ISS starter has a mechanism Solenoid to energise
motor (SL2)
that conjunctionally shifts the pinion gear and energises
Solenoid to shift pinion (SL1)
the motor for rotation. This means it is not capable of Pinion Gear
restarting when the engine is rotating – or while the
engine is coasting after the vehicle is stopped. With the
TS starter, if the engine is rotating fast, the motor is first Ring Gear

energised to increase the pinion gear speed and then the

pinion gear is shifted forward when the rotation of the EMS
Engine Speed
ring gear and pinion gear are close. When the engine is
turning slowly enough for the two gears to be connected, AE Starter
the pinion gear is first moved forward and then the Conjunctional control of pinion gear shift and motor energisation by one solenoid
motor is powered. This allows the engine to be re-engaged
(and re-started) by the starter motor during the 0.5 to 1.5
Solenoid
seconds of dead time that the engine rpm is simply falling
from idle
(~600 rpm) to zero rpm. Therefore, depending on the
engine, up to 1.5 seconds can be shaved off from restarts. Ring Gear
EMS

EMS: Engine Management System

Re-start time during engine run down Re-start during engine run down

Current: Wait then restart Ú Development: Immediatly restart

Engine restart time (S)

1.5
Restart demand Development Current
Engine speed

(TS Starter)

p80% Waiting Time

1

0.5
Current Waiting Time (S)
Re-Start Time
0 Up to 1.5 seconds
Development (TS Starter) Current

25
 DENSO Starters | Stop & Start Technology
Starters | Stop & Start Technology

> Idling Stop System (ISS)

TS Starter Engineering Key Point

Separately control pinion gear forward movement and motor energisation according to engine speed

Timing of engine
High engine (ring gear) speeds Low engine (ring gear) speeds
restart requests
Motor on Ú Pinion shift Pinion shift Ú Motor on
Restart demand Restart demand

800 800
600 600
(rpm)

(rpm)
Flow of control
400 400
200 200

0 0.2 0.4 0.6 0.8 1.0 0 0.2 0.4 0.6 0.8 1.0
(S) (S)
Energise the motor to increase the rotational speed of the pinion Move the pinion gear forward and then energise the motor.
gear and then move the pinion gear forward when the pinion gear
and ring gear are rotating at almost the same rate.
> Idling Stop System (ISS)

Engine restart requests: The driver’s actions identified as requests to restart the engine, such as releasing the brake pedal

Permanently Engaged (PE) Starter

DENSO’s Permanently Engaged (PE) Starter eliminates the starter’s noise.
pinion gear shifting mechanism and mounts to the engine so that the
However, the PE Starter does not need time to engage the mating
starter is permanently engaged with the flywheel.
gears. It has a new mechanism that enables the pinion gear to
The PE Starter is “Change of Mind” capable and delivers the quickest be constantly meshed with the engine ring gear. When a restart
and quietest restart times of all starter motor-based systems, while is needed, the motor is energised, and immediately re-cranks the
improving the overall fuel-saving potential depending on the overall engine. The PE Starter also achieves a compact and lightweight
system approach. design by using a compact high-speed motor and planetary gears.

Conventional ISS starters have to shift the starter motor pinion The PE Starter is jointly developed with Toyota Motor Corp and is
forward, mesh it into the ring gear, and then disengage the two gears primarily used in Toyota models equipped with ISS, such as the Auris
after the engine starts - all of which can result in restart delays and and Yaris models sold in Europe since 2009.

Permanently Engaged Starter

Features
>>Double Rubber Shock Absorber: Shock absorption at engine Pinion Gear

start and starting noise reduction.

>>Slip Disk Shock Absorber: Flywheel with built-in one-way Ring Gear
clutch protection.
One-Way Clutch
>>Reversal Prevention Clutch: Engine oscillation reduction at
Reversal
engine stop and prevention from turning in the wrong direction. Prevention
Slip Disk Clutch
>>Flywheel with built-in one-way clutch: The flywheel requires During engine start: locked
Shock
After engine start: idling
a special clutching mechanism to disengage ring gear from Absorber
Double Rubber
engine after engine restart. Flywheel Shock Absorber

PE Starter Engineering Key Points Benefits

>>At engine start: starting noise Engine: 2.0L, Gasoline Mission: 5MT
At engine start At engine stop
reduction by the double rubber
shock absorber and starting time Fuel Economy Noise Time Vibration
reduction by the permanently
engaged system.
>>At engine stop: vibration reduction
by the reversal prevention clutch.

*Fuel cut before vehicle stop

**Fuel cut after vehicle stop
p Development * **
¢ Conventional p ¢ p ¢ p ¢ p ¢

26
DENSO Starters | Stop & Start Technology

Starters | Stop & Start Technology

> Idling Stop System (ISS)

Further ISS Approach

An ISS approach is more than just starter technology. There are many additional products and components that can be added to any ISS
approach to enhance comfort and convenience and improve powertrain performance. Many of these products better manage energy in a
vehicle, which also translates into fuel efficiency.

Key Points
>>Using a TS (Tandem Solenoid) starter helps the engine to restart quickly and seamlessly after it shuts down.
>>In-rush Current Reduction (ICR) Relay – sometimes when the engine is restarted, there can be a “dimming” of lights, or a reset of
some devices due to the large electrical demand placed on the system by the starter motor. An ICR Relay located between the battery
and starter motor reduces the system voltage dip that happens every time the starter cranks the engine.
>>A high efficiency alternator recovers the energy wasted while the car is slowing down and transforms it into electric power.

> Idling Stop System (ISS)

>>DENSO’s lithium-ion battery pack stores regenerated power and supplied it to electric and electronic components, reducing the power
generation needed by the alternator.
>>DENSO’s cold storage system helps maintain the cabin’s temperature when a vehicle with ISS is at a stop and air conditioning is no
longer powered.
>>DENSO’s brushless electric water pump will help maintain a vehicle’s temperature when a vehicle with ISS is at a stop and the heater
is on. The electric water pump is smaller yet more energy efficient because it uses less power.

System Structure
Idle Stop System

Cold Storage Case

Cold Storage Evaporator
Electric
ECU for AC
Water Pump

Stop/Start Brake System

System ECU
or integrated into Cool air
the Engine Brake
High-efficiency Tandem Vacuum Sensor
Management
Alternator Solenoid Starter System ECU

Current Sensor
with a built-in
Battery Charge
Controller

Lithium-ion
Battery Pack
Lead-acid
Battery

Auxiliary Machines
Navigation
Headlight, Ignition Coil, Electric Electric
System, Audio
Heater etc. Electronic Power Steering Oil Pump
System etc.
Throttle etc.

27
 DENSO Starters | Replacement Guide
Starters | Replacement Guide

The following general information has been established as a common instruction for starter removal and installation. Refer to the
appropriate Vehicle Manufacturer’s Service Manual for specific information corresponding to starter removal and installation procedures
and safety precautions for the vehicle.

Always disconnect the cable from negative (-) battery terminal before replacement and wait at least 90
seconds after disconnecting the cable to prevent any type of activation. After replacement, connect
the cable to negative (-) battery terminal.

Personal injury or damage to the equipment and its components may occur if this step is not performed.

Removal
1. Identify each wire connection, and note the location of each on the starter.
2. Disconnect and remove the battery cable from the starter.
3. Disconnect and remove all other wires from the starter.
4. Loosen the starter mounting bolts. Do not remove the bolts yet.
5. Support the starter and remove the bolts holding the starter in place. Set the bolts and starter aside. Be sure to note fastener size
and location before removing the starter.
6. Inspect the flywheel or flexplate ring gear through the starter-mounting port for tooth damage. Replace as necessary.

Installation
1. Physically compare the replacement starter to the original starter. Compare the wire connector locations, front housing clocking,
adjusting hole locations and drain hole position to the original starter.
2. Support the starter and fasten it into position. Torque the mounting bolts to the vehicle manufacturer’s recommended specifications.
3. Re-connect the previously removed wires to their proper location on the starter. Be sure that there is no interference between the wire
harness and other components. Torque all threaded fasteners to the vehicle manufacturer’s recommended specifications.
4. Re-connect the battery cable to its proper location on the starter. Do not over tighten battery cable retaining nut. See the vehicle
manufacturer’s recommended specifications for correct torque value.
5. Re-connect the negative battery cable to the battery. Do not over tighten negative battery cable. See the vehicle manufacturer’s
recommended specifications for correct torque value.
6. Check the starter for proper operation.

28
DENSO Starters | Troubleshooting

Starters | Troubleshooting
> Diagnostic Chart

Starting System Diagnostic Chart

Starting problems are not always easy to identify and can cause unnecessary starter replacement. In troubleshooting, it is important to
study closely the trouble symptom, thereby narrowing possible causes down to one or two. Most common problem symptoms, related
possible causes and corresponding corrective actions are listed in the chart below.

Symptom Possible Cause Corrective Action

> Diagnostic Chart

1. Dead or defective battery.
1. Check battery state of charge.
2. Melted fuse/fusible link.
Recharge if possible. Replace if necessary.
3. Loose connections.
2. Replace as necessary.
4. Ignition switch or relay, neutral start switch,
3. Clean and tighten connections.
clutch start switch contacts in poor condition.
Engine does 4. Replace components as necessary.
not crank 5. Magnetic switch contacts worn away.
5. Replace starter.
6. Malfunction of the magnetic switch
(pull-in coil or plunger). 6. Replace starter.

7. Malfunction of starter motor assembly (layer short, 7. Replace starter.

brush wear).
8. Check engine.
8. Mechanical problem in engine.

1. Weak battery. 1. Check battery state of charge. Recharge

if possible. Replace if necessary.
2. Loose or corroded connections.
Engine cranks 2. Clean and tighten connections.
too slowly to start 3. Poor magnetic switch contact.
3. Replace starter.
4. Starter motor assembly malfunction
(layer short, brush wear). 4. Replace starter.

The starter rotates, 1. Damaged or worn starter pinion gear 1. Check gears for damage or wear.
but cannot crank or engine ring gear. Replace starter or ring gear.
the engine 2. Defective over-running clutch. 2. Replace starter.

1. Damaged or worn starter pinion gear 1. Check gears for damage or wear.
or engine ring gear. Replace starter or ring gear.
The starter does 2. Defective magnetic switch. 2. Replace starter.
not stop rotating
3. Defective ignition switch or control circuit. 3. Replace defective components as necessary.

4. Binding ignition key. 4. Check key for damage.

1. Abnormal bushing wear. 1. Check and replace the starter if necessary.

Abnormal 2. Wear on the starter pinion gear or engine 2. Check gear tooth tips for damage or wear.
starter noise ring gear tooth tips. Replace starter or ring gear.

3. Starter pinion gear sliding failure. 3. Replace starter.

29
 DENSO Starters | Troubleshooting
Starters | Troubleshooting

> Inspection

Inspection
Visual Inspection
Begin with a thorough visual inspection of system and components.

System Cables & Wires

>>Make sure all connections are intact, tight, clean and corrosion free.
>>Check wires for wear, insulation damage and other physical damage.

Starter Physical Condition

>>Check for oil, dust, water contamination due to usage in severe environmental conditions.
> Inspection

>>Check for damaged holes, terminals, thread due to incorrect tightening or fixing.
>>Check for overheated/deformed label, discolored terminals due to abnormal starter usage such as prolonged cranking.
>>Check for teeth wear, discoloration, hard pinion rotation due to abnormal starter usage such as prolonged cranking.

Electrical Tests
On-Vehicle Inspections Cables
Battery
Battery inspection Terminals
>>Before performing any electrical system diagnosis or repair, make sure the
battery has been visually inspected, performance tested and is fully charged.
>>Battery, battery cables, battery terminals condition affect the ability of the Electrolyte
battery to provide sufficient power. Low

>>Charge the battery and check the open circuit voltage.

>>If 12.6 Volts (full charge) or above is not measured, replace the battery and
continue to evaluate the charging system.
>>If the open circuit voltage is 12.6 Volts or above, perform battery load-test.
Electrolyte For Terminals
>>A load-test measures the battery’s ability to deliver power. OK Corrosion
>>Also, if the battery can not be recharged, there may be a charging problem
that causes starting system problems. In this case, inspect the charging
system and its components. Case for Electrolyte
Damage or Level
Cracks

Starting system current draw test

>>Connect voltmeter positive (+) lead to positive (+) battery terminal.
>>Connect voltmeter negative (-) lead to the negative (-) battery terminal.
>>Connect the clamp-on amp probe pickup around the negative (-) battery cable.
>>While cranking the engine, observe the voltage and current readings.
>>Cranking speed should be normal (approximately 200-250 rpm).
>>Current draw should be at or below the maximum limit that is specified by
vehicle manufacturer’s repair manual.
Digital Voltmeter
>>Cranking voltage should be at or above the minimum limit that is specified by
vehicle manufacturer’s repair manual. Cranking voltage spec. is usually 9.6
Volts approximately at 20-25°C.
- +
Battery
Note: Test can be performed with:
>>Electronic tester Clamp-on Amp Probe
>>Carbon pile load tester
>>Cranking the engine. If cranking the engine, Ground
1. Disable the fuel or ignition system to keep
the engine from starting during the test. High current draw and low cranking speed usually indicate a defective starter.
2. D O NOT crank the engine for longer than This can be caused by starter motor layer short, worn brushes or bushings,
10 seconds at a time. mechanical blockage. High current draw may also be caused by engine problems.
3. W ait a minimum of 60 seconds before A low cranking speed with low current draw, but high cranking voltage, usually
cranking engine again to cool the starter. indicates excessive resistance in the starter circuit.
30
DENSO Starters | Troubleshooting

Starters | Troubleshooting
> Inspection

Starting system voltage drop test

>>Connect the voltmeters according
to the illustration. While cranking the
engine, observe voltage readings.
>>Calculate voltage drop on the starting
circuit by subtracting (-) Voltmeter B
Digital Voltmeter A
from Voltmeter A. Voltage loss should
not exceed 0.5 Volt.
>>If total loss exceeds 0.5 Volt, there is
Ignition Neutral
excessive voltage drop somewhere in
- + Switch Safety

> Inspection
the circuit, proceed with starter positive Battery Switch
and negative side voltage drop tests
and control circuit voltage drop tests
to isolate the cause and repair the fault.
Ground
Ground

Note: Test can be performed with:

>> Electronic tester
>> Carbon pile load tester Digital Voltmeter B
>> Cranking the engine. If cranking the engine,
1. Disable the fuel or ignition system to keep the engine from starting during the test.
2. DO NOT crank the engine for longer than 10 seconds at a time.
3. Wait a minimum of 60 seconds before cranking engine again to cool the starter.

High resistance in starter positive or negative side reduces current to the starter motor and causes slow cranking speed or hard cranking.
High resistance in starter control circuit reduces current to the magnetic switch and causes improper operation or no operation at all.
Every wire, cable and terminal connection has the potential to create excessive voltage loss that can affect starter performance. Checking
the voltage drops provide helpful tips to find hidden problems that can cause a starting system problem. Voltage always flow through the
path with the lowest resistance. Therefore, if there is a high resistance somewhere in the circuit, some of the voltage flow through the meter
and creates a voltage value on meter’s display.

Digital Voltmeter

Ignition Neutral
- + Switch Safety
Switch
Battery

Ground
Ground

Positive side voltage drop test

Note: Test can be performed with:
>>Connect voltmeter positive (+) lead to positive (+) battery terminal, > Electronic tester
and the voltmeter negative (-) lead to the battery terminal on the > Carbon pile load tester
starter. While cranking the engine, observe > Cranking the engine. If cranking the engine,
1. D
 isable the fuel or ignition system to keep the engine from
the voltage reading on voltmeter.
starting during the test.
>>If voltage drop is 0.5 Volts or less, the resistance at positive side
2. DO NOT crank the engine for longer than 10 seconds at a time.
is acceptable. 3. W
 ait a minimum of 60 seconds before cranking engine again to
>>If voltage drop is more than 0.5 Volts, there is excessive resistance. cool the starter.

31
 DENSO Starters | Troubleshooting
Starters | Troubleshooting

> Inspection

>>Excessive resistance could be caused by a damaged battery cable, poor connection at battery or starter terminal, or a defective
magnetic switch.
>>Clean and tighten the battery terminals and perform the following voltage drop tests to isolate the cause and repair the fault.
>>While cranking the engine, check the voltage drop between positive (+) battery terminal and cable connection. Connect the voltmeter
positive (+) lead to the positive (+) battery terminal and the voltmeter negative lead (-) to the battery cable clamp. Acceptable cable
connection voltage drop should be zero Volt.
>>While cranking the engine, check the voltage drop of positive (+) battery cable. Connect the voltmeter positive (+) lead to the clamp on
the positive (+) battery cable and the voltmeter negative (-) lead to the end of the cable at the starter. Acceptable battery cable voltage
drop should be 0.2 Volts or less.
>>While cranking the engine, check the voltage drop across the magnetic switch. Connect the voltmeter positive (+) lead to positive (+)
> Inspection

battery terminal on the starter, and the voltmeter negative (-) lead to the starter motor terminal. Acceptable voltage drop across the
magnetic switch should be 0.3 Volts or less.

Negative side voltage drop test

>>Connect voltmeter positive (+) lead to a clean spot on starter motor >>If voltage drop is 0.2 Volts or less, the resistance at negative side
housing, and the voltmeter negative (-) lead to the negative (-) is acceptable.
battery terminal. While cranking the engine, observe the voltage >>If voltage drop is more than 0.2 Volts, there is excessive
reading on voltmeter. resistance.

Ignition Neutral

- + Switch Safety
Switch

Battery

Ground
Ground

Digital Voltmeter

Note: Test can be performed with:

>>Electronic tester 2. DO NOT crank the engine for longer than 10 seconds at a time.
>>Carbon pile load tester 3. Wait a minimum of 60 seconds before cranking engine again to
>>Cranking the engine. If cranking the engine, cool the starter.
1. Disable the fuel or ignition system to keep the engine from
starting during the test.

>>Excessive resistance could be caused by poor starter mount >>While cranking the engine, check the voltage drop between
on vehicle, poor battery ground or a loose connection. negative (-) battery terminal and cable connection. Should be
>>Check if the starter is properly installed. zero Volt.
>>Make sure all the ground points/straps between the engine and >>While cranking the engine, check the voltage drop of negative (-)
chassis are secured. battery cable from the battery to the engine block. Should be 0.2
>>Clean and tighten the battery terminals and perform the following Volts or less.
voltage drop tests to isolate the cause and repair the fault such >>While cranking the engine, check the voltage drop between the
as similar to the positive side. starter housing and the engine block. Should be 0.2 Volts or less.

32
DENSO Starters | Troubleshooting

Starters | Troubleshooting
> Inspection

Starting system control circuit voltage drop test

>>If the battery is in good condition but starter does not crank >>Put the gear shift selector in park or neutral for vehicles with
the engine, the problem could be a poor ignition switch automatic transmission, depress the clutch pedal for the
connection or execessive resistance in the starter control vehicles with manual transmission. Crank the engine and
curcuit that can reduce the voltage available to the magnetic observe the voltage reading on voltmeter.
switch. Symptoms of this problem will be pinion gear does not >>Also, check the voltage drop across the ignition switch and
engage or engage improperly. neutral start switch or clutch start switch.
>>Excessive resistance could occur at ignition switch contacts, >>Check whether voltage readings are within appropriate vehicle
park/neutral start switch or clutch start switch, or circuit wiring manufacturer’s specs. or not. Adjust or replace the defective
and connections. Perform the following voltage drop tests to switches as necessary.

> Inspection
isolate the cause and repair the fault.
>>Connect the voltmeter positive (+) lead to the positive (+) battery
terminal and the voltmeter negative (-) lead to the magnetic
switch terminal on starter.

Note: If cranking the engine:

1. Disable the fuel or ignition system to keep the engine from starting during the test.
2. DO NOT crank the engine for longer than 10 seconds at a time.
3. Wait a minimum of 60 seconds before cranking engine again to cool the starter.

Starter Relay An alternative voltage drop method

One of the possible causes of the starting system problems Checking the voltage drop across each component of the starting
could be a defective starter relay (if equipped). Perform continuity curcuit is an alternative method to locate the cause of excessive
test to identify whether the relay is defective or not. Check for voltage drop. Leave the voltmeter positive (+) lead connected to the
continuity with the relay de-energised and energised. If any of positive (+) battery terminal and move the voltmeter negative (-) lead
these tests do not match the vehicle manufacturer’s specified back through the circuit toward the battery. Continue to test each
results, replace the starter relay. connection while cranking the engine until a noticeable decrease in
voltage drop is detected. The cause of the excessive voltage drop
will be located between that point and the preceding point.

33
 DENSO Starters | Troubleshooting
Starters | Troubleshooting

> Inspection

ISS Troubleshooting Outline

>>A scan tool is necessary for vehicles with ISS system to isolate the cause and repair the fault of ISS system or its components.
>>As an example, the active test and work support are required for starter inspection on the vehicle and removal/installation checks.
>>The test monitor function is useful for dividing up the system for troubleshooting.
>>The number of times that the starter is operated is much greater in vehicles equipped with ISS. As an example, the number of starter
operations is counted in Toyota vehicle applications equipped with PE starters. When the number reaches a determined value,
a warning light illuminates to urge
starter replacement.
Scan Tool
>>When parts related to ISS are
For Starter Inspection,
> Inspection

replaced, it is necessary to register Removal and Installation

or reset the relevant parts on scan LIN
tool to instruct engine ECU. Active Test
Forces Drive,
>>In most vehicles, when the battery ISS Engine
Starter Inspection
terminals are disconnected or CAN
connected, the vehicle must be
driven for a certain amount of time Alternator In-Vehicle Inspection
such as 15 to 40 minutes until ISS
Active Test, Forces Drive,
system operates. If the vehicle is not Data Monitor, Separation Separate into System
driven, ISS system will be prohibited of Malfunctioning Systems Malfunction or
and Components Alternator Malfunction
for the specified amount of time. Work Support
Reset Number of Starter
Operations

E074108E

Starter Test bench inspection

If a starter will be tested on a test bench, follow
the procedures found in the test bench instruction
manual to conduct a starter performance test. This
test will determine if the starter output is within its
performance specification, preventing unnecessary
starter replacement.

If the test bench results indicate the starter output

to be out of specification, replace the starter.

If the starter output is within specification during

bench testing, resolve problems in the remainder
of the vehicle’s starting circuit and other
electrical circuits that may affect starting system
performance. Refer to the vehicle manufacturer’s
service manual for the procedures necessary
to identify and correct additional starting circuit
problems.

34
DENSO Starters | Troubleshooting

Starters | Troubleshooting
> Inspection

Function Tests Terminal C

Perform each test in a short period of time

(three to five seconds).
1. Pull-in test
1) Remove the nut and the lead wire
from terminal C.
2) When connected as per the figure:
Battery (+) 1 1 Terminal 50
Battery (-) 1 1 Body and Terminal C

> Inspection
>>Verify that pinion gear springs out.

Terminal 50

Test Wire

Terminal C

2. Holding test
1) From the pull-in test conditions,
check the pinion gear remains
out even after the test wire is
disconnected from terminal C.
2) Remove the ground wire.

>>Verify that pinion gear returns.

Terminal 50

Terminal C

3. Return test
When connected as per the figure:
Battery (+) 1 Terminal C
Battery (-) 1 Body and Terminal 50

>>Verify that pinion gear springs out.

If terminal 50 is removed during this state,

the magnetomotive forces of both coils will
balance out.

>>Verify that the pinion gear instantly returns.

Terminal 50

35
 DENSO Starters | Troubleshooting
Starters | Troubleshooting

> Inspection

Performance Tests

Test Item Outline

No-load test Observe the maximum rotation speed and current when there is no load.

Load test Observe the required current to generate the specified torque, and the rotation speed at that time.

Lock torque test Observe the torque and current when the rotation speed is 0 under excessive load.
> Inspection

Caution:
> Starter torque and rotational speed varies greatly according to the battery capacity. Conduct tests when the battery is properly charged.
> A large amount of current flows, so perform the tests quickly.

S1

1. No-load test
Purpose 50 M
- +
A
To verify the assembly and main contacts condition.
Method +
Tachometer
>> Connect as shown in the figure, and close S1 to startup the starter.
V
>>Measure the rotational speed, voltage, and current when the
starter rotation stabilizes. -
>>Check if the results are within the manufacturer’s specs or not.

S1

2. Load test
Purpose
To verify starter output under the regulated load.
50 M
- +
A
Method
>> Connect as shown in the figure, and close S1 to startup the starter. +
Tachometer
>>Apply the brake to the ring gear and adjust until the current V
matches the test standards. Torque Meter -
>>Measure the voltage, torque and rotational speed.
>>Check if the results are within the manufacturer’s specs or not.

3. Lock torque test S1

Purpose
To verify that the specified torque is output.
50 M
(Also observe the clutch sliding.) - A
+
Method
>> Connect as shown in the figure, and close S1 to startup the starter. +
>>Lock the ring gear with the brake.
V
>> Measure the voltage, current, and torque while the ring gear Torque Meter
is locked.
-
>>Check if the results are within the manufacturer’s specs or not.

36
DENSO Starters | Troubleshooting

Starters | Troubleshooting
> Q&A

Q&A Section
Does the starter turn the engine too slowly?
>>The battery must be fully charged (12.6 Volts) and the battery cables, terminals and case in good, clean condition. This includes the frame
and body ground connections and connections at the starter motor and magnetic switch.
>>Excessive engine oil viscosity, particularly in cold weather environments, will reduce the ability of the engine to rotate. This increase
in engine drag will be transmitted to the starter during starter engagement, reducing its performance capability.
>>Engine modifications change the operating characteristics of the engine. If modifications are performed, a chance of additional forces acting
against the starter will be introduced. The starter should be replaced with one matched to the new operating characteristics of the engine.

Does the starter fail to crank the engine?

> Q& A
>>The starter is designed to turn at a specified rotational speed to crank the engine. If there is a high resistance somewhere in the starting
control circuit, or the battery connections or cables are corroded or dirty, this will cause the starter to turn slower than the specified
rotational speed. Be sure that all the circuit connections and contacts, battery connections and cables are clean and secured properly.
This includes the frame and body ground connections and connections at the starter motor and magnetic switch.

Does the starter rotate without rotating the engine?

>>The flywheel or flexplate transfers the rotational energy of the starter to the engine. If the starter is rotating but not the engine, check all
teeth on the flywheel or flexplate ring gear to see if they are excessively worn, damaged or missing. Inspecting the flywheel or flexplate
ring gear teeth can be performed through the starter mounting port if an inspection plate on the bell housing is not available.
>>A defective starter drive assembly could cause similar symptoms as a damaged flywheel or flexplate. If the starter pinion gear meshes
properly with the flywheel or flexplate ring gear and does not rotate, the starter should be inspected for mechanical wear or damage.

Does the magnetic switch make operating noise when activated?

>>If clicking is heard when activating the starter control circuit and the starter does not rotate, the magnetic switch may not be receiving the
voltage necessary to be fully activated. Check the starter control circuit for failed or damaged components and wiring, and loose, dirty
or corroded connections.
>>If the magnetic switch is receiving proper voltage, the magnetic switch may have burnt contacts. Follow the vehicle manufacturer’s
procedures and safety precautions to inspect the starter.
>>If magnetic switch does not make any operating noise when activated and the starter does not rotate, the magnetic switch may be defective
due to malfunction of pull-in coil or plunger. Follow the vehicle manufacturer’s procedures and safety precautions to inspect the starter.

Is there audible noise when trying to start the engine?

>>Audible noise may be associated with physical damage to the flywheel or flexplate. Inspect the flywheel or flexplate completely for
cracks, dents, roundness balance, etc.
>>An inoperable starter magnetic switch or a damaged starter may also cause audible noise. Follow the vehicle manufacturer’s procedures
and safety precautions to inspect the starter.

What does continuous or prolonged cranking cause?

>>Low battery voltage results in excessive current flow to the starter motor.
>>Starter motor commutator is overheated, bars on commutator lift from insulator.
>>Damage to brushes and/or brush holder assembly occurs.

Commutator surface is glazed. Commutator surface is burned. Commutator segment bar has separated,
Commutator segment bars bent. Commutator segment bars missing. raised and bent (distorted).

37
 DENSO Starters | Troubleshooting
Starters | Troubleshooting

> Q&A

What does occur if the ignition key is excessively held in start position?
>>Starting control circuit stays closed and causing burnt magnetic switch main contacts.
>>Starter pinion gear rotates at flywheel speed (engine speed) and causing overrunning.
>>Commutator bars separate and causing damage to brushes, brush holder assembly and commutator.
> Q& A

Melted wire coating and case discoloration. Separated commutator segments. Damage to commutator, brushes and brush
Burnt odour. holder assembly.

What are the causes of pinion gear teeth damage and meshing problems?
>>New starter is fitted to the original flywheel which has damaged or worn ring gear teeth (or just the opposite).
>>Driver fault (engagement of the ignition key while the engine is operating).
>>Mechanical problem (ignition switch or starter magnetic switch main contacts stuck closed).

Minor case of re-engagement (will cause flywheel Moderate case of pinion re-engagement. Extreme case of pinion re-engagement.
damage and have difficulty engaging into
flywheel).
What are the signs of starter abuse and mishandling?

Solenoid cover has been struck repeatedly with a Damage to the terminal could cause ground Starter to engine mounting bolt hole broken off
hammer or some other foreign object. contact with housing. due to mishandling, improper installation or
over-torquing of the engine bolt.

ID tag has been overheated and has shrunk. Melted insulation on the starter end housing thru Normal starter (left), pinion gear fully retracted.
This is a sign of excessive heat. bolts. This is a sign of starter abuse (overheated). Overheated (right), pinion gear not fully retracted.
Overheating affects tension in the return spring.

38
DENSO Starters | Troubleshooting

Starters | Troubleshooting
> Q&A

What are the key aspects when selecting an aftermarket starter?

A replacement starter does not have to look like the original one, but it has to function the same and also match the fitting interface
dimensions. There are numerous OE part numbers that are used by vehicle manufacturers, hence why aftermarket suppliers consolidate OE
part numbers as much as possible. The most important features are:

>>Long lifetime and maintenance-free

>>Fitting interface dimensions such as fixing hole locations, diameters, thread sizes, terminal locations, etc
>>Number of pinion teeth, direction of rotation
>>Power output capacity should meet the vehicle’s requirements

Caution: Never use a starter with lower power output capacity for a vehicle that requires a starter with higher power output capacity.
For example, do not use a 1.4 kW rated starter for a vehicle that requires a 2.0 kW rated starter. Excessive current flow will cause

> Q& A
premature starter failures.

Is it possible to use an Idling Stop System (ISS) starter instead of a

conventional starter for the same car model or engine application?
If the ISS starter’s overall construction and main dimensions (as shown in the
illustration) are equivalent or smaller compared to a conventional starter, ISS starter
may replace it. If the dimensions are very close or a little bigger, it is best to perform
an installation check for fitting verification.

Also, replacing the conventional starter with an ISS type should not require
unique controls, software or engine modifications such as DENSO Advanced
Engagement (AE) Starter. It works like a conventional planetary starter but includes
key design features like dual layer, long-life electrical brushes as well as an unique
structure and pinion spring mechanism (AE mechanism).

Indeed ISS starters are built with high durability and performance features to
ensure extended lifetime for increased number of starting cycles even under
severe environmental conditions. Replacing with an ISS starter should therefore
be considered as an upgrade though it may be costly.

What are the latest developments in starting systems?

With the rise of electrification to save fuel and reduce emissions towards achieving
the stringent emission legislation in 2020, advanced developments have been
implemented to starting systems.

In comparison to the various hybrid concepts, emerging start-stop technologies for

combustion engines have already changed the manufacturing landscape. A unique
starting system with robust starter motor is required for vehicles with expanded
DENSO is a major developer of small,
idling stop-start features such as DENSO’s “Change of Mind” starter motors which long life ISGs with diverse OEMs.
have the capability of restarting before the engine reaches zero rpm.

When it comes to Hybrid Electric Vehicle’s (HEV’s), rotating electric machine

technology Integrated Starter Generator (ISG) replaces the alternator and starter
motor for light electrification system architectures such as belt-driven ISG for micro/
mild HEV’s with low voltage systems.

>>ISG allows the HEV’s engine to instantly and quietly restart (via the belt drive
system) after the idle stop, so functions as a starter.
>>Like a conventional alternator, the ISG produces electric power when the vehicle
is running, which is used to supply electric devices and/or to charge the battery.
>>The ISG can help to decelerate the vehicle by generating electric power, which
is called regenerative braking. The electric power generated charges the battery,
reducing fuel consumption. Key benefits
>>If a clutch disconnects the ISG and the compressor from the engine during the idle >>Instant and quiet restarting
stop, the ISG can drive the air-conditioning compressor via a belt. >>Generates electric power
>>Reduced fuel consumption

39
 Get inside
• 100% OE specification
• All ‘new in box’
• Ncore
o re-manufactured units and no
surcharge or returns policy
• Extensive applications
Maximum efficiency
• Market leading list
•

As one of the world’s largest automotive component suppliers, DENSO is a global leader in developing and manufacturing rotating
machines. Our unwavering commitment to outstanding quality, design and innovation mean that our Starters and Alternators are
selected as original equipment by carmakers worldwide – winning many supplier and international quality awards along the way. As well
as delivering unique,
OE coverage of Toyota and a wide range of European marques such as Fiat, Opel, PSA, BMW, Ford, Volvo and Land Rover, the
programme is continually being updated and expanding.

www.denso-am.eu
PART 2
DENSO Alternators
 DENSO Alternators | Characteristics
Alternators | Characteristics

> System outline

The alternator is driven by the engine, via the belt. It converts mechanical energy
into electrical energy and supplies the required power to the various electrical loads.
When power supplied by the alternator does not match the required electrical load
(when all
the electrical equipment is in use, or when the engine speed is low during idling
etc.), the battery temporarily supplies extra power to the electrical equipment. However,
during normal driving the alternator re-charges the battery to the original strength.

The engine speed changes constantly according to the driving conditions. This means
that the alternator speed also changes, with the generated voltage changing in tandem. It
is the role of the regulator to control the generated voltage of the alternator, supplying the
various electrical loads with the appropriate voltage. The regulator also ensures that the
> System outline

battery is charged appropriately.

Charging Mechanism Alternator Ignition Switch

Battery

Progress of • Alternator
(kg/kW)
Alternator • Contact Point Type Regulator
Minimisation 10 Conventional Type Alternators
• Alternator with IC regulators
• Improved electromagnetic circuit
• Uses IC regulators, in-built components
• (Contact point type also avaible as an option)

III Type Alternators

Weight/Output • Improved cooling performance

5 • High-density coils
SC Alternators
• Employs segment conductor stator
• IC regulator minimised to 1 chip

1970 1980 1990 2000 (Year)

42
DENSO Alternators | Characteristics

Alternators | Characteristics
> How Alternators work

Basic Principles of Electricity Generation N S

When a magnet is moved in the vicinity of a coil, a voltage is generated.
The stronger the magnet, the larger the voltage generated and the faster
the magnet is moved, the larger the voltage. Also, the greater the number
of windings in the coil, the larger the voltage.

N S

> How Alternators work

Basic Principles of Electricity Generation

Generating an Alternating Current

In an actual alternator, a rotor fulfils the role of the magnet in the above figure,
Basic Principles of the Alternator
while a stator coil fulfils the role of the coil. The rotor does not move in and out
N
from the stator; instead, it rotates within the stator itself. As the rotor rotates
Stator Coil
the N pole or the S pole of the rotor alternately approach the stator coil, and
Rotor a current is generated in the stator coil.
N S
+

0
0° 90° 180° 270° 360°
S -
1 Cycle
+ Alternator With 3-Phase Coil

0
Excitation Electricity 0° 90° 180° 270° 360°
-
N
The alternator generates 3-phase alternating current, which
offers significant advantages when compared with a single N
phase alternating current. Taking the example of a simple
bipolar alternator, in a single phase, current is received from a A
generator with one coil. In a 2-phase current, the generator has A
B
two coils placed at an interval of 90º, while in a 3-phase current B
there are 3 coils placed at an interval of 120º.

A stator and rotor such as those below are C

Power Source for Excitation C
installed in actual alternators.

Coil A

A A B B CC
3-Phase
Electromotive
Force

Stator Rotor Coil C Coil B 0° 120° 240° 360°

0° 120° 240° 360°

43
 DENSO Alternators | Characteristics
Alternators | Characteristics

> How Alternators work

Rectification Rectification Action of the Diode

One objective of the alternator is to charge the Signal

battery, so the alternating current cannot be used
unchanged. A diode (solid state rectifier) is used to Current
P N
perform rectification by converting the alternating
current into direct current.

An actual alternator has 3-phase alternating current, Can only flow

so 6 diodes are used for 3-phase full wave rectification. in this direction

+ -
In (a), a large voltage is generated between phases I
> How Alternators work

and II, and the current flows to the load through diode Schematic Diagram of 3-Phase Full Wave Rectification
1 and flows back from diode 5.
(a) 1 2 3 (d) 1 2 3
In the next process as shown in (b), the voltage becomes
higher between phases I and III, and current leaves
Battery
through diode 1 and comes back through diode 6.

Following on in sequence to (c), (d), (e) and (f), 4 5 6 4 5 6

the current size and direction flowing to each phase
and wire is varied, however the current is always
(b) 1 2 3 (e) 1 2 3
delivered to the load in a constant direction.

This rectification action is performed by a rectifier. (a) 1 2 3 (d) 1 2 3

4 5 6 4 5 6
4 5 6 4 5 6

(b) (c) 1 2 3 1 2 3 (e) 1 2 3(f) 1 2 3

Rectifier

4 5 6 4 5 6

4 5 6 4 5 6
(c) 1 2 3 (f) 1 2 3

Field current is controlled to

4 5 6 4 5 6 maintain a constant voltage

Generated Voltage Control Alternator B

The voltage generated in the alternator increases as the rotating speed

of the rotor increases. If the generated voltage is then directly supplied to
F
an electrical load such as a battery or light, increases in alternator speed
Regulator
can result in electrical equipment failure (excessive charging, blown lights,
etc.).

Therefore, a constant output must be maintained. The alternator controls

this by varying the current flowing to the field coil.
E
When the rotational speed is high or the load is light and the output Field Coil
voltage seems ready to exceed the specified value, the current flowing to
the field coil is reduced. This ensures that the output voltage is always
within the specified value range.

The component that performs this control is called the regulator.

The IC regulator is currently the most common type.

44
DENSO Alternators | Types

Alternators | Types
> Conventional Type

In recent years vehicle power consumption has increased with the emergence of information and communication products, such as navigation
systems and electronic control products, which are designed to improve comfort and safety and make vehicles environmentally friendly.
To meet the demand for additional power, alternators must produce electric power more efficiently whilst being smaller in size and lighter in
weight. DENSO has been developing a variety of alternators that meet those requirements for a variety of vehicles.

> Conventional Type

Most of the alternators produced by DENSO can be broadly classified as follows in terms of construction and features.

History of the Alternator

1970 1980 1990 2000

Alternator First Appears

Conventional Type Alternator

Type III Alternator SC Alternator

Conventional Type Alternator Type III Alternator SC Alternator

Conventional Type
The alternator pulley is integrated with the rotor and is driven by the engine
crankshaft pulley via a belt. The conventional alternator also uses an
external cooling fan. The engine thus drives the rotor, generating AC in
the stator coil, while the rectifier converts this AC into DC.

Features and benefits

>>Produced higher output by using a cold forged rotor core to improve
magnetic circuit.
>>Reduced size and weight by using internal built-in IC regulator.

45
 DENSO Alternators | Types
Alternators | Types

> Type III

This is an alternator with small internal fan. Instead of the large exterior fan used in conventional alternator, two compact built-in fan
blades are used. This creates an AC generator with faster speed and lower noise. The high-density coils and improved cooling produce
a compact and lightweight alternator with high output.
> Type III

Features and benefits

>>Increased output by optimising stator and rotor sizes to improve the magnetic circuit and decreasing the pulley diameter for a faster rotor.

>>Two fan blades integrated with the rotor reduce alternator size, weight and fan noise.

46
DENSO Alternators | Types

Alternators | Types
> SC Type

In 2000, DENSO introduced the world’s first SC (Segment made the SC alternator 20 percent lighter and increased the output
Conductor) alternator using a rectangular segment conductor 50 percent higher than a conventional type.
(angular copper wires) for its stator coil.
In addition, the regulator is a miniaturized single-chip IC type,
Compared to the conventional type, the SC alternator reduces coil resulting in a compact and lightweight alternator with both high
resistance and thermal losses by 50 percent, and raises the winding efficiency and output.

> SC Type
density (space factor) from 45 percent to 70 percent. Thus, DENSO

Features and benefits

>>Compact, lightweight, high output and high efficiency. The winding density of the stator coil is increased by using an innovative winding
method and a rectangular segment conductor. Low magnetic noise. Magnetic pulsation (the main component of magnetic noise in the
alternator) is reduced 90 percent due to use of both dual and staggered windings.

>>Small and multifunctional IC regulator.

47
 DENSO Alternators | Types
Alternators | Types

> SC Type

Segment Conductor Stator

Features and Benefits

Lower Electrical Resistance Improved air flow Suppression of Small Package Size
EMF* Fluctuation
> SC Type

Low
Inertia
Rotor

Vertical segment insertion

Reaction Force
Smooth Air Flow
Current

Armature
through formed windings
Outline
New Outline

30 degree 1 Chip Regulator

Time
Dual circuit Stator & Rectifier
cancels Armature Reaction Force
High Slot-fill
using square section wire * Electro Magnetic Force

Fuel economy improvement

48
DENSO Alternators | Types

Alternators | Types
> SC Type

DENSO Excellence
> DENSO has developed the high output >>In 2000, DENSO developed the world’s first SC (segment
SC alternators that provide rated output conductor) alternator using a rectangular segment conductor
currents of 165, 180, 200, 220 and 240 for its stator coil, reducing coil resistance by 50 percent.

> SC Type
amps; higher than well-known typical
SC alternators rated up to 150 amps. >>The DENSO SC alternator adopted dual windings and rectifiers,
achieving smaller size, lighter weight, higher efficiency and
> DENSO alternators are the smallest and lower noise.
lightest in the world for their output.
>>DENSO further improved the stator coil connection method of
>>Vehicles, especially luxury models and large vehicles, now the SC alternator to develop the compact and high output SC
require higher output alternators, as vehicle power consumption alternators.
increases, and engine revolution at idle is lowered to reduce fuel
consumption. To meet these requirements, DENSO developed the >>To counteract higher heat production due to higher output,
high output SC alternators. DENSO increased the surface area of the rectifier cooling fins
to nearly twice the size of conventional fins, improving the cooling
>>DENSO’s high output alternators, the world’s first air-cooled ability of the rectifiers.
type with output level up to 240A, enables a large vehicle, which
traditionally requires a larger, more expensive water-cooled
alternator or two air-cooled alternators, to have only one compact
air-cooled alternator.

DENSO’s SC Alternator Characteristics

Rear End Frame

Battery Terminal

Drive End Frame

IC Regulator

Pulley

Bearing
Rear End Cover

Rotor

Brush Holder

Rectifier

Fan

Stator

49
 DENSO Alternators | Types
Alternators | Types

> SC Type

Rotor Pulley
The rotor functions to create a magnetic field and rotates in Two types of pulley are used: a solid pulley and a pulley with
conjunction with the shaft. The rotor primarily consists of a pole clutch (One-Way Clutch or Decoupler). The solid pulley has a
core (magnetic pole), field coil, slip rings and shaft. large contact surface with a belt and does not slip easily, so it
can provide a large pulley ratio. The pulley with clutch is used
The pole core is shaped into claws and encloses the field coil.
> SC Type

in engines (diesel etc.) with relatively large torque fluctuations.

When current flows through the field coil, one side of the pole
It only engages with the rotor shaft in a forward direction and
core fully magnetizes to become a North (N) pole, and the
the belt rotates the rotor via the pulley. In the reverse direction,
other side becomes the South (S) pole. The claw pole type
the clutch function disengages the pulley and rotor, thus
enables all the poles to be magnetised using the one field coil.
functioning to release the engine torque fluctuation.
Fan
Pulley with Clutch
An integrated cooling fan is installed on both sides of the rotor Solid Pulley
to blow air to the front, rear and interior for cooling. When
Locks
current flows through the coils and diodes, the temperature Disengages (Engages
of the parts increases and can cause damage to the system. Rotor Shaft)
Cooling via the fan is therefore necessary.

Brush Holder
Components are brushes, springs, brush holder. Two brushes Stator
slide around the circumference of the slip rings to supply The stator consists of a stator core and stator coil, and is
current to the rotor (field) coil so that a magnetic field can be supported by front and rear end frames. The stator core is a
created. magnetic flux passage that enables the effective interaction
of magnetic flux from the rotor pole cores in the stator coils.
Battery Terminal
The alternator output terminal that supplies current to the Conventional stator cores use a system where circular wires
car’s battery. are wound together, leaving many gaps between them. The SC
type uses a segment conductor system in which square-shaped
Drive and Rear End Frames
angular copper wires are inserted and joined tightly, in place of
The end frames have heat release holes and fins to improve
a stator with a winding system. The SC system increases the
cooling. The drive (front) side end frame is press fit to the
copper wire space factor (the space ratio between the winding
stator and helps improve stator cooling. The rectifier, brush
gap and the winding in cross section) of the stator core. As
holder and IC regulator are attached to the exterior of the rear
a result, stator resistance is half that of the conventional type
side end frame to improve serviceability.
and heat generation is reduced, thereby dramatically improving
Rear End Cover power output and efficiency in a compact configuration.
Covering and protecting the rectifier, brush holder and IC
regulator, all of which are mounted on the rear end frame. Segment Conductor

Bearing
SC Type
Bearings are used to support the rotor assembly. Rear bearing A Cross
is mounted on rotor shaft and the front bearing is mounted to Joint SC Section
A
(Segment Conductor) Type Diagram
the drive end frame. A

Conventional
Type B Cross
B Circular Type Section
B
Diagram

Stator connections
Y Connection (Dual Winding Type) Delta Connection (Staggered Winding Type)
The Y connection features a dual winding system with two sets of In the delta connection, an additional winding is connected in
three-phase windings (A and B). These are provided to cancel out series with each of the conventional
each other’s magnetic windings, and the phases are
fluctuations that are staggered. This suppresses magnetic
A B
created at the stator. As fluctuation generated by the stator, and
a result, the magnetic reduces the amount of magnetic noise
noise that is generated generated by the alternator. This is
by the alternator is mainly used in SE alternators (a simple
dramatically reduced. and compact form of SC Type).

50
DENSO Alternators | Types

Alternators | Types
> SC Type

Rectifier Positive+ + Side Diode Positive ++ Side Diode Terminal B

Y Connection (Dual Winding Type)
As the stator contains two sets of
Terminal B A B
three-phase windings, the number
A1 B1
of diodes has been increased from B1
A2 B2
B2

> SC Type
six to twelve (Zener diodes). The A3 B3
A1
rectifier works in the same way as A2
the conventional type to rectify the
three-phase AC generated in the - -
Negative Negative- - E
coil into DC. Stator coils A and B Side Diode Side Diode
A3 B3 E047797E
are connected to the rectifier as
shown in the figure. Terminal B Terminal B

Delta connection (Staggered Winding Type)

Positive++
Rectifier uses one set of six silicon diodes. Side Diode
P3 P1
This is mainly used in SE alternators (a simple P2
and compact form of SC Type). P1
P3

- E E
Negative - P2
Side Diode

IC Regulator
In contrast to the conventional IC regulator in which the regulator circuit is formed on a ceramic board, a
miniaturised multifunctional IC regulator that integrates the circuit into a single-chip is used in an SC alternator
resulting in a compact and lightweight configuration.

The basic function and operation of the regulator is very similar to conventional IC regulators. However, some
types of the single-chip IC regulator enable communication between alternator and engine ECU to finely
control alternator voltage regulation.

Outline of New Charging (Compact Alternator)

Control Systems
Electrical Load
The New Charging Control (e.g. Blower, Motor, Wipers)
(IC Regulator)
System control alternator
voltage generation in Current Value Battery Current
Battery Condition Sensor
accordance with various Voltage is Calculated Voltage Value
Generation
driving conditions through Instruction Battery
Driving Conditions Temperature
the communication between Sensors Battery
are Determined
alternator IC regulator and
Engine ECU Battery Temperature
engine ECU, thus reduce the Sensor
vehicle’s fuel consumption.

The engine load caused by the generation of voltage in the alternator is lessened by reducing the generated voltage during acceleration
and by increasing it during deceleration. This improves the engine’s fuel efficiency. During idling and constant speed driving, the generated
voltage is adjusted to meet the target value for which is determined depend on battery and driving conditions.

Driving Conditions Acceleration Consant Speed/Idling Deceleration

Generation
Stopped Generation Battery
(Battery Restrained Charge
Discharge)
Circuit Diagram Alternator Electrical Alternator Electrical Alternator Electrical
Load Load Load

Battery Battery Battery

Charging Condition Battery Discharge at Low Voltage Open Voltage Battery Charge at High Voltage

51
 DENSO Alternators | Types
Alternators | Types

> SC Type

Example: Operation of an IC regulator with communication function

• A duty ratio (on/off ratio) signal is sent from the M (Monitor) terminal of the IC regulator to the engine ECU. This informs the engine ECU
corresponding to the alternator’s generating condition.

• The engine ECU calculates the optimum voltage to generate based on the driving conditions, electrical load and the battery condition.
The ECU issues instructions for generating this optimum voltage by sending a duty ratio (on/off ratio) signal to the IC regulator.
> SC Type

• The IC regulator uses the engine ECU’s instructions to control voltage generation in the alternator.

Example: IC Regulator Circuit Diagram

M Engine
ECU
IG
B
Ignition
Switch

Charge
IC Regulator Lamp
P
L

Load
F Battery

E E

LIN Communication- Compatible IC regulator

Nowadays, LIN (Local Interconnect Network) communication- Signals for the gradual excitation power generation function,
compatible IC regulators are used in the charging control systems regulating voltage and excitation current command value are received
of new vehicle models that are commonly equipped with the from the engine ECU by the LIN terminal to adjust voltage and
Stop & Start System. Bidirectional, multiplex communication via generate power. The signals for each value detected (i.e. power
the LIN is used between the engine ECU and the IC regulator to generation status, communication status, etc.) by the control circuit
precisely control alternator voltage regulation. LIN uses single-wire are transmitted to the engine ECU from the LIN terminal.
communication lines to transmit digital signals based on special
protocols (communication regulations) at 9.6 kbps or 19.2 kbps.

LIN Type IC Regulator for the SC Alternator LIN Type IC Regulator Circuit Diagram

B
B
E/G
M ECU
IG B
E
Tr1
RLO
LIN Engine Stop
Control & Start ECU
L Tr2 Circuit
LIN LIN
F
P
Tr2 Load
Battery

52
 Technical Overview DENSO Alternator
Discovering DENSO Technology

Volume
Type III Alternator SC, SE Alternator
SC Type

Type III

Drive End Frame Rotor IC Regulator

Drive End Frame Rotor Teminal B

Bearing Teminal B
Bearing Weight
IC Regulator
Type III SC Type

Rear End Cover

Rear End Cover

Pulley
Pulley
Brush Holder
Fan Feature of the product
Fan
Brush Holder

Stator Rectifier
Noise High
Stator Type III efficiency
Rectifier
Fan Fan SE Type

Low SC Type
noise

Output Current (A)

SE Alternator: Has a simple construction based on the SC alternator in a compact configuration

53
Alternators | Wall Chart
 DENSO Alternators | Replacement Guide
Alternators | Replacement Guide

The following general information has been established as a common instruction for alternator removal and installation. Refer to the
appropriate Vehicle Manufacturer’s Service Manual for specific information corresponding to alternator removal and installation procedures
and safety precautions for the vehicle.

Always disconnect the cable from negative (-) battery terminal before replacement and wait at least 90
seconds after disconnecting the cable to prevent any type of activation. After replacement, connect the
cable to negative (-) battery terminal.

Never disconnect a battery cable while the engine is running. Doing so can damage the alternator as well
as other electronic components of the vehicle.

Removal
1. Identify each wire connection and note the location of each on the alternator.
2. Disconnect the wires from the alternator.
3. Loosen the alternator pivot bolt but do not remove the bolt yet.
4. Loosen the tension assembly’s lock nut or bolt and turn the adjustment bolt so that drive belt tension is reduced far enough to allow
belt removal. Some vehicles may be equipped with an automatic, spring-loaded tensioner. Rotate the spring-loaded tensioner using
the appropriate tool far enough to allow drive belt removal.
5. Remove the drive belt from the alternator.
6. Support the alternator and remove the bolts holding the alternator in place. Set the bolts and alternator aside. Be sure to note bracket
orientation and fastener length/location before removing the alternator.
7. Inspect the condition of the wiring and connectors. Inspect for worn wire ends, continuity, loose or broken connectors, corrosion and
pliability. Repair or replace as necessary.

Installation
1. Physically compare the new alternator to the original. Compare the housing and pulley offsets, pulley size and type, pivot and
adjustment hole locations, wire connector locations and terminal configurations with the original alternator.
2. Install the mounting bracket(s) but do not completely tighten the bolts yet.
3. Support the alternator and fasten it into position but do not completely tighten the bolts yet.
4. Install the drive belt. If the drive belt was found to be worn, stretched, cracked, oily or glazed during the charging system inspection,
replace the belt.
5. Set the belt tension while tightening the mounting and adjusting bolts. Be sure to set the belt tension and torque the mounting bolts to
the vehicle manufacturer’s recommended specifications.
CAUTION: Do not pry or hit the alternator housing to adjust the belt tension.
6. Check the drive belt alignment between the alternator pulley and other drive pulleys. Be sure there is no interference between the drive
belt and other components.
7. Re-connect the wire connector to its proper location on the alternator. Be sure there is no interference between the wire harness and
other components.
8. Re-inspect all components are correctly installed, all threaded fasteners properly torqued and there is no interference between
components.
9. Re-connect the battery negative cable.
10. Start the engine and be sure there is no interference between components. Let the engine idle for 5 minutes to accustom the drive
belt.
11. Turn the engine off and re-adjust the drive belt if necessary. Re-inspect all components are correctly installed, all fasteners properly
torqued and there is no interference between components.
12. Re-test the charging system to verify that it is performing according to the vehicle manufacturer’s specifications.

54
DENSO Alternator | Troubleshooting

Alternators | Troubleshooting
> Diagnostic Chart

Charging System Diagnostic Chart

A defective charging system may cause various problems. In troubleshooting, it is essential to start identifying symptoms related to
these problems in order to narrow possible causes down to one or two. Most common problem symptoms, related possible causes and
corresponding corrective actions are listed in the chart below.

Symptom Possible Cause Corrective Action

1. C
 heck charging, ignition and engine fuses,
1. Blown fuse. replace as needed.
Charging System/
Battery warning 2. Lamp burned out. 2. Replace lamp.

> Diagnostic Chart

lamp is not ON
3. Wiring connections loose. 3. Tighten loose connections.
with key switch ON
and engine at stop 4. Defective relay. 4. C
 heck relays, if used, for continuity
condition and proper operation.
5. Defective regulator.
5. Replace alternator.

1. Defective battery or battery connections.

1. C
 heck battery and battery terminal connections
2. Blown fuse or fusible link. Replace as needed.

3. Defective wiring. 2. Check fuse and fusible link Replace as needed.

NO charge
4. Defective alternator. 3. Check voltage drop.

5. E
 xcessive electrical load due to additional 4. Replace alternator.
electrical accessories such as off-road lighting,
5. Replace alternator with upgraded one.
etc.

1. Defective battery. 1. Replace battery.

Constantly 2. P
 oor contact at voltage detection pin/terminal 2. M
 ake sure the contact area is clean
overcharging of alternator. and corrosion free.

3. Defective regulator. 3. Replace alternator.

1. Adjust tension or replace.

1. Insufficient belt tension.
2. M
 ake sure the battery connections are clean
2. Poor contact at battery connections.
and corrosion free.
3. Poor alternator ground.
Intermittent charging 3. Make sure alternator is properly grounded.
4. Open or shorted diodes.
4. Replace alternator.
5. Open or shorted stator windings.
5. Replace alternator.
6. Defective regulator.
6. Replace alternator.

1. L
 oose/worn belt due to service life, binding,
contamination . 1. Adjust tension or replace the belt.

2. D
 efective/worn bearings due to too tight belt 2. Replace alternator.
Abnormal noise adjustment, water ingress, etc.
3. Replace alternator.
3. D
 efective diode due to severe vibration, improper
4. Inspect and make sure installation is properly
testing, jump start, reverse polarity, etc.
done.
4. Misalignment due to improper installation.

55
 DENSO Alternators | Troubleshooting
Alternators | Troubleshooting

> Inspection

Inspection
Visual Inspection
Begin with a thorough visual inspection of system and components.

Drive belt Alternator Physical Condition

>>Belt condition >>Check for oil, dust, water contamination due to usage in
>>Alignment severe environmental conditions.
>>Proper tension >>Check spark marks on housing that are signs of battery
reverse polarity.
System cables & wires
>>Check wear on fixing lugs/surfaces on housing that are
>>Make sure all connections are intact, clean and corrosion free.
signs of hammering due to improper installation.
>>Check wires for wear, insulation damage, and other
>>Check pulley rotation for audible noise.
> Inspection

physical damage.

Cables
Electrical Tests
Battery Terminals

Electrolyte
Precautions Low
>>Do not operate the alternator with its B+ terminal disconnected.
>>Do not disconnect the battery while the alternator is rotating.
>>Never ground the alternator B+ terminal, it has battery voltage at all times.
>>Never expose the alternator to water. Electrolyte
For
OK
Case for Terminals
On-Vehicle Inspections Damage or Corrosion
Cracks Electrolyte Level
Battery Inspection
>>Before performing any electrical system diagnosis or repair, make sure the battery has been visually inspected, performance tested
and is fully charged.
>>State of battery, battery cables, battery terminals condition affect the ability of the battery to hold the charge.
>>Charge the battery and check the open circuit voltage. If 12.6 Volts (full charge) or above is not measured, replace the battery and
continue to evaluate the charging system. If the open circuit voltage is 12.6 Volts or above, recommended to perform battery load-test.
A load-test measures the battery’s ability to deliver power.

Voltage drop test

Voltage drop test positive side (output circuit)
- +
>>Attach the meter’s positive lead to the alternator output terminal Battery
(B+) and meter’s negative lead to positive (+) battery post.
>>Run the engine at approximately 2000 rpm with the lights,
blower motor and radio on. The reading on meter should be
less than 0.2 Volts.

Voltage drop test negative side (ground circuit)

>>Attach the meter’s negative lead on the alternator case, or ground
strap if equipped, and the positive lead on the negative (-) battery post.
>>Run the engine at approximately 2000 rpm with the lights, blower - +
Battery
motor, and radio on. The reading on meter should be 0.2 Volts or less.

56
DENSO Alternators | Troubleshooting

Alternators | Troubleshooting
> Inspection

Checking the voltage drops in positive and negative sides provides helpful tips to find hidden problems that can cause a charging
problem. Voltage always flow through the path with the lowest resistance. Therefore, if there is a high resistance somewhere in the
positive or negative side, some of the voltage flow through the meter and creates a voltage value on meter’s display.

>>If a voltage reading greater than 0.2 Volts is observed at voltage drop test positive side, it indicates there is excessive resistance
somewhere in the positive side that causes a voltage drop. Check all the wiring and connector pins/terminals are intact, clean and
corrosion free.
>>If a voltage reading greater than 0.2 Volts is observed at voltage drop test negative side, make sure all the ground connections and
contact area is clean and corrosion free. Also, make sure that there is no broken, loose or missing ground points/straps between the
engine and chassis.
>>If a voltage reading less than 0.2 Volts is observed at voltage drop tests, continue with further electrical tests.

> Inspection
Alternator Output Test
Regulated voltage inspection
Run the engine at approximately 2000 rpm and then check the regulated voltage at alternator output stud (B+) terminal when current
output reaches approximately 10 A (Refer to the test standards and values designated by the relevant vehicle manufacturer).

Output current measurement

Turn the headlights to high beam, the blower switch to high, and so on. Then measure the output current at an engine rotational speed of
approximately 2000 rpm. Current at this time should be at or above the standard values designated by the relevant vehicle manufacturer.

Caution: The standard values differ according to the vehicle manufacturer. Refer to the appropriate Original Equipment Manufacturer’s
service manual for specific information corresponding to alternator specifications.

Alternator Test bench inspection

> If an alternator will be tested on a test bench, follow the procedures found in the
test bench instruction manual to conduct an alternator performance test. This
test will determine if the alternator output is within its performance specification,
preventing unnecessary alternator replacement.
> If the test bench results indicate the alternator output to be out of specification,
replace the alternator.
> If the alternator output is within specification during bench testing, resolve problems
in the remainder of the vehicle’s charging circuit and other electrical circuits that
may affect charging circuit performance. Refer to the vehicle manufacturer’s service
manual for the procedures necessary to identify and [V] <Example>
correct additional charging circuit problems.
Regulated Voltage Range
Regulated voltage verification 15

>>Set the alternator on the test bench.

Regulated
>>Verify that the test bench is set up and that the charge light is ON. Voltage 14

>>Run the alternator, and adjust the rotational speed and load to the standard values.
>>Regulated voltage should be within the standard values at this time. 13

>>Caution: Perform measurements quickly; the regulated voltage has the temperature characteristics
shown in the figure due to the IC regulator specifications. -30 0 30 60 115 135 [°C]
Temperature of IC Regulator
E047900E

Output Current test 200

180 Output Voltage

>>Set the alternator on the test bench. Constant at 13.5 V
160
>>Verify that the test bench is set up and that the charge light is ON. 140

>>Run the alternator, and adjust the rotational speed and voltage to the standard values. 120
Output
>>Current should be within the standard values at this time. Current (A) 100

>>Caution: Current output gradually decreases while the testing cycle is repeated due to 80

60
alternator temperature increase. Output 40
Characteristics 20

0 2 4 6 8 10 12 14 16 18

Alternator Speed (x10³ rpm)

57
 DENSO Alternators | Troubleshooting
Alternators | Troubleshooting

> Q&A

Q&A Section
What is the condition of the battery?
This is an electro-chemical device. It converts chemical energy into electrical energy. The
battery has three primary functions.
>>Source of electrical energy to start the engine.
>>Act as a voltage stabiliser in the electrical system.
>>Supply current when electrical demand exceeds alternator output.

A visual inspection and a performance test of the battery must always be performed before
inspecting the charging system.

The battery must be fully charged (12.6 Volts or above) and the battery cables, terminals and
> Q&A

case in good and clean condition.

What is the biggest drain on battery charge?

Electrical consumers can be split into 3 groups: continuous, long-time and short-time.
Thus, the electrical load requirement is not steady. The drain on the battery charge is therefore impacted by usage habits or even the time
of year as some systems are seasonal (A/C systems, heated seats).

Engine management system components such as ignition, fuel injection are part of the continuous consumer group and are therefore
causing a considerable drain caused by an increased number of sensors and actuators required in modern vehicles.

However the biggest drains on battery at component level will most likely come from long-time and short-time consumers such as
headlights, rear window defroster, wiper motors, blower motor.

What are most common problems that cause battery to run down?
>>Old or service life ended battery that is not able to hold the charge.
>>Charging system problem that is preventing battery to be recharged.
>>A key-off drain due to a stucked switch or relay, computer or electronic modules that are not shut down.

If the battery and alternator are inspected (as previously mentioned) and no issues were found, the root cause of discharged flat battery
may come from a key-off drain.
In older cars, key-off drain should not exceed few milliamps. On the other hand, for modern vehicles (fitted with computers and various
electronic modules), it can be around 50 to 100 milliamps or even more during a period of time i.e. 15 to 30 minutes after the ignition
is switched off in order to keep memory alive. Indeed this is a general assumption, always refer to the vehicle manufacturer’s service
information corresponding to key-off drain specification if available.

Does a charging system/battery warning light indicate a charging system problem?

>>Ignition switch ON, engine not running
The warning lamp should illuminate.
>>Ignition switch ON, engine running
The warning lamp should illuminate briefly then turn OFF.
>>Weak Battery
A weak battery can cause the warning lamp to illuminate during high amperage draw.
>>Low Idle
A low idle can cause the warning lamp to illuminate dimly.
>>Poor Wiring
Corroded, broken, loose or worn wires/connections could cause the warning lamp to illuminate
during idle.
>>Open Warning Lamp
Some charging systems will not properly operate if the warning lamp bulb fails.

58
DENSO Alternators | Troubleshooting

Alternators | Troubleshooting
> Q&A

Are any fuses open?

Check the fuses in all the fuse box(s). An open fuse indicates circuit problem(s) which may have an affect on the charging circuit.
Check the owners manual or the vehicle manufacturer’s service manual for the location of each fuse box.

C C C C

Normal Burned Out

> Q&A
Normal

Is the fusible link(s) open?

There may be several fusible links controlling battery voltage to the
vehicle’s electrical circuits. If a fusible link is open, supply voltage will be
completely lost to all electrical systems or to the electric circuit(s) that
the open fusible link controls. Check the owner’s manual or the vehicle
manufacturer’s service manual for the location of each fuseable link.
Wire Burned Open

Is the alternator’s drive belt tension within specification?

Check the tension and condition of the alternator drive belt.
>>Too loose
If the drive belt is too loose, it will slip around the pulley and causing the alternator to charge irregularly or not at all.
>>Too tight
If the drive belt is too tight, internal bearing damage will cause premature alternator failure.

Replace

Alternator drive belt condition can affect the transfer of power from the engine crank pulley to the alternator pulley. Old, damaged or worn
drive belts can prevent the alternator to charge the battery properly. Service life of a drive belt differs depending on the conditions under
which the belt is being used. However, it is recommended to replace the drive belt when replacing the alternator.

Is there an alternative way to check whether alternator works fine or not?

Another way to check the alternator is using a portable/handheld oscilloscope. Observing the “ripple pattern” can identify open or shorted
diodes as well as problems in the stator coil. A good ripple pattern should look like the figure below. Any irregularities in the ripple pattern,
means that there is open or shorted diode(s) and/or stator winding(s). Most of the modern alternator test benches have the option to
check the ripple pattern and to detect defective diode(s).

Ripple Pattern

59
 DENSO Alternators | Troubleshooting
Alternators | Troubleshooting

> Q&A

Can an alternator fail because of a poor wiring/ground contact or loose connection?

A poor wiring or ground contact increases resistance and causes a voltage drop in the electrical circuits. In this case, flow of
the current through the charging circuit is reduced. Due to this problem, the battery is not able to be fully and properly recharged,
causing the alternator to keep charging it at a higher rate than normal. This may cause overheating and premature alternator failure.

Another common problem that causes failure such as in below images is a loose battery cable connection to the alternator. It
results in intermittent or no charge alongside a discolored and/or melted alternator output (B+) stud terminal.
> Q&A

What could be the root cause of repeated alternator failures?

It may be caused by burnt out diode(s) due to an open circuit or a high resistance between the alternator output (B+) and the positive (+)
battery connections. In such instances, charging current will flow through the diodes from an alternative route towards the battery. This
alternative route will cause excessive current flow through the diode resulting in overheating and failure. Therefore, perform a thorough
inspection and voltage drop tests to isolate any problems and avoid repeated alternator failures.

A similar effect may occur when the alternator is forced to charge a discharged battery or when the battery is able to be charged
but not able to set up normal resistance. In such cases, the alternator will be instructed to charge the battery to the maximum rate and
overloaded for prolonged periods. It will cause the alternator to overheat. As a result, the diodes as well as the stator windings and
connections inside the unit can be damaged and failed. Therefore, check the battery carefully and replace if necessary.

Overheating can also occur if the alternator is located in a space with poor airflow. Especially, when the alternator is working under full load
at slow speed in conditions where cooling is insufficient. This may result in premature alternator failures due to overheating.

ID tag has been overheated

Diode has been overheated
and has shrunk. This is a
and failed
sign of excessive heat

60
DENSO Alternators | Troubleshooting

Alternators | Troubleshooting
> Q&A

What could be the other root causes of alternator failure due to Rectifier (Diode Bridge)
bad diode(s)?
Another most common cause of alternator failure due to one or more
bad diode(s) within rectifier is the reverse polarity. Therefore, NEVER
apply reverse polarity to the alternator. If the alternator is connected to
the battery with a polarity reversal, the diode(s) can explode, melt or be
perforated by high current flow and fail. Moreover, all other diodes may
have abnormal current leakage.

Besides, the diode(s) can be damaged severely when the battery

is disconnected while the engine is running or during a jump start.

> Q&A
Good Diode Bad Diode

Alternator failed because of defective bearing due to water ingress. What could be the root cause of this failure?
Water ingress in bearing causes grease deterioration. Bearing rotation under corrosion and poor lubrication due to grease deterioration
causes fatigue and premature failure of the bearing. Although the alternator will be viewed as the main cause of failure, it is most likely
related to the location of the alternator in the engine bay or usage in severe environmental conditions exposing the part to excessive water
contamination. If the alternator is not shielded sufficiently and continuously exposed to water contamination by tires or if it is located
under the windshield draining tube (in line with pulley), water spillage in static condition creates water stagnation and results with water
ingress in bearing. Alternator bearings are waterproof due to double lip construction, however they may not withstand prolonged or
continuous excessive water contamination.

Defective Front Bearing

61
 DENSO Alternators | Troubleshooting
Alternators | Troubleshooting

> Q&A

What are the key features of selecting an aftermarket alternator?

A replacement alternator does not have to look like the original one, but it has to provide an equivalent output as well as the same pulley
specifications and fitting interface dimensions.
There are numerous OE part numbers for alternators used by vehicle manufacturers, hence why aftermarket suppliers consolidate OE part
numbers as much as possible. The most important key features are:

>>Long lifetime and maintenance-free

>>Regulator type is the key feature due to voltage regulation characteristics
>>Pulley type, diameter and number of ribs
>>Fitting interface dimensions such as fixing lug locations, fixing hole diameters, wiring connector, etc.
>>Current output capacity should meet the vehicle’s requirements
> Q&A

Caution: Never use an alternator with lower current output capacity for a vehicle that requires an alternator with higher current output
capacity. For example, do not use a 80A rated alternator for a vehicle that requires a 120A rated alternator. Overloading an alternator
will cause premature alternator failures.

Which in-car technology/features is likely to have the biggest impact on the evolution of alternators?
Developments called Smart or Intelligent Charging allow the alternator’s regulator and the engine ECU to communicate and interact with
each other improving the reliability and precision of the alternator output control, the electrical power generation and distribution as well
as the mechanical power input requirements. Additionally, new features are generated such as boost charging times, enhanced engine
performance and idle stability, soft start delay, load response control as well as new diagnostic functions.

Communication between alternator’s regulator and ECU is enabled with signals which are Pulse Width Modulated (PWM). Various Smart
or Intelligent Charging systems are being used but currently LIN (Local Interconnect Network) based systems are the mainstream and are
becoming industry standard. Basically, alternators with LIN regulator use bidirectional, multiplex single-wire LIN Bus communication lines
to transmit digital signals based on special LIN protocols.

How will alternator technology change over the next 5-10 years?
EVs are radically changing the manufacturing landscape and are set to play a big part in the future of the automotive industry. This
will enable further advances in alternative motor-generator technology. In comparison to the various hybrid concepts, which incur
significant costs for return-on-investment through fuel economy, emerging start-stop technology will continue to offer a far more cost-
effective solution.

The market is currently dominated by start-stop systems that use enhanced robust starter motor and high-efficiency alternator and will
still dominate the market alongside other fuel saving solutions such as high output regenerative braking and boost recuperation. These
can make a big contribution toward achieving the stringent emission legislation in 2020 and beyond.

In terms of alternator technology for combustion engines with start-stop system, the main design is unlikely to change radically but
more advanced improvements will be introduced to increase efficiency whilst reducing size, weight and noise such as DENSO eSC line high-
efficiency alternators achieving up to 80% efficiency in a compact body thanks to reduced rectification loss by use of MOSFETs and reduced
iron/copper loss by improved design. Such developments further contribute to the fuel economy and reduce CO2 emissions.

62
DENSO Europe B.V.
Hogesweyselaan 165
1382 JL Weesp
The Netherlands

Tel: +31 (0)294 493 493

Fax: +31(0)294 417 122

marketing@denso.nl
www.denso-am.eu
Printed in the Netherlands
DESA16UK03MM