Field Information Bulletin FIB-2004-35-REV-00
Family Subject Date Group
All engines Low Coolant Level Safety Switch Test November, 30 2004 15
Procedure.
Introduction:
This bulletin explains about the Low Coolant Level Safety Switch checks in field. The purpose of
this document is to improve the diagnostic capability in field to determine the condition of the LCWL
switch using standard multimeter. This FIB is intended to prevent, working LCWL switches being
removed and replaced erroneously.
The purpose of this switch is to intimate that the Coolant level in the radiator top tank or the in
expansion tank in case of Heat Exchanger is lower than the permissible limit. The output of this
switch can be used to trigger an alarm or shut down the engine.
Construction:
The working principle of this switch is very simple. It uses the theory of continuity of circuit between
two electrically conducting materials. The switch is constructed with two electrodes, which are
electrically isolated. The two electrodes are alternately excited (electrically)
Working: When the conducting medium (Coolant), comes in between the two electrodes, the circuit
is completed and the output of the switch is brought to zero. If there is no conducting medium
(Coolant) between the two electrodes, the output of the switch goes high. Three wires are brought
out of the switch, they are as follows:
1. Red : Supply (24 Vdc positive to the switch).
2. Brown : Output
3. Black : Return (24 Vdc negative to the switch).
CUMMINS INDIA LIMITED, CUMMINS DIESEL SALES & SERVICE (I) LTD.
Kothrud, Pune 411 038, India. 35A/1/2, Erandawane, Pune – 411 038, India.
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Test procedure:
Following procedure should be adopted in field to test whether the LCWL switch is operative. Follow
step 1-3 to check whether the switch is working
1. Remove LCWL switch from radiator / Expansion Tank. Clean both the electrodes using dry
cloth. Cleaned the LCWL Switch properly & solved the matter.
2. Connect 24 Vdc supply to the switch at terminal 1 and 2 as shown in the picture below. Use
a standard multimeter to measure the output of the switch. If the switch is functioning and
the supply to the switch is switched ON and the switch is not dipped in water, the LED on
the switch will start glowing in RED colour. The output at terminal 2 with respect to terminal
3 shall be 24 Vdc.
CUMMINS INDIA LIMITED, CUMMINS DIESEL SALES & SERVICE (I) LTD.
Kothrud, Pune 411 038, India. 35A/1/2, Erandawane, Pune – 411 038, India.
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3. Maintaining the connections made in Step 2 mentioned above, dip the switch in plain water
and ensure that both the electrodes are dipped in the water thoroughly. If the LCWL Switch
is OK, as soon as both the electrode comes in contact with water, the LED on the switch will
start glowing GREEN and the output of the switch at terminal 2 with respect to terminal 3 will
be 0 Vdc.
Multimeter showing 0 Vdc output from the switch
when dipped in coolant.
Once the switch is found OK as per Step 3, check whether the supply to the switch from the engine
harness exists.
4. Ensure that there is continuity between the two connected (connector on the switch and on
the engine harness). This can be check by measuring the voltage at the connector on the
switch side. This ensures that when the two connectors are in contact the switch is getting
24 Vdc input from the battery through the engine harness. Voltage at terminal 1 with respect
to terminal 3 should be 24 volts DC.
NOTE – DO NOT REPLACE THE LCWL SWITCH WITHOUT PERFORMING CHECKS AS
ABOVE.
CUMMINS INDIA LIMITED, CUMMINS DIESEL SALES & SERVICE (I) LTD.
Kothrud, Pune 411 038, India. 35A/1/2, Erandawane, Pune – 411 038, India.
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