Cooling Fan Circuit and A/C High Pressure Switch Circuit- Test

204

TM 9-2320-312-24-2

Troubleshooting Section

Note: Not all vehicle manufacturers, or all trucks

Start the "Cooling Fan" test and stop the "Cooling

for a manufacturer use the Caterpillar cooling fan

Fan" test. At the same time, watch the voltage

circuit. Prior to troubleshooting, determine if the

test lamp.

vehicle is using the ECM cooling fan circuit.

Note: A multimeter can not be used in place of the

Check the following items in order to determine if a

voltage test lamp when the ECM output is tested.

vehicle is using the ECM cooling fan circuit:

Expected Result:

The "Fan Control Type" parameter must be

The voltage test lamp turns on when the test is

programmed to "On/Off" or one of the variable

active. The voltage test lamp turns off when the test

speed options. The Caterpillar factory default is

is not active.

None.

"A/C Fan On Time" is programmed between one

Results:

second and 600 seconds.

Yes The output for the ECM cooling fan relay

A wire is present in the ECM vehicle harness

is functioning properly.

connector J1/P1 (terminal 11) which is output 5

Repair: If a problem still exists, then the problem

(cooling fan solenoid). This occurs if an On/Off

is in the wiring that was installed by the OEM.

type of fan is used.

Repair the problem or send the vehicle to the

Perform the Special Test for the "On/Off Cooling

OEM dealer for repair.

Fan". Access each menu in the order that follows:

Verify that the repair eliminates the problem.

"Diagnostics", "Diagnostic Tests", and "Special

Test". Activating and then deactivating the circuit

should cause the air solenoid to click if the circuit

STOP.

is working properly.

The following background information is related

Repair: Temporarily connect a test ECM. Use

to this procedure:

the special test on the electronic service tool to

check the ECM cooling fan circuit. If the problem

Cooling Fan

is resolved with the test ECM, install the suspect

The signal for the cooling fan is provided by the

ECM. If the problem returns with the suspect

ECM in order to control the cooling fan. An input

ECM, replace the ECM.

from one of the following items may cause the fan

to turn ON:

Verify that the repair eliminates the problem.

Engine coolant temperature sensor

STOP.

Air inlet temperature sensor

i01606147

Cooling Fan Circuit and A/C

Exhaust brake

High Pressure Switch Circuit

PTO on/off switch

- Test

OEM installed A/C high pressure switch

SMCS Code: 1359-081-ZS; 1408-081; 1802-081-ZS

Manual fan override switch

System Operation Description:

A control unit for the A/C may be connected to

the A/C high pressure switch (input 11) instead of

Use this procedure under the following situation:

a switch.

Use this procedure to determine if the cooling fan

The output for the cooling fan is intended to connect

(output 5) or the A/C high pressure switch (input

directly to the circuit for the cooling fan solenoid.

11) is operating correctly.

Program the "Fan Control Type" parameter to

"ON/OFF". The fan will be off when the ECM output

is ON (energized). When the ECM activates the fan,

the fan will remain on for a minimum of 30 seconds

except for the following conditions: