Cooling Fan Circuit and A/C Compressor Clutch Circuit

196

TM 9-2320-312-24-2

Troubleshooting Section

Repair: Temporarily connect a test ECM. Ensure

Cooling Fan

that the "Engine Monitoring" and the "Coolant

The signal for the cooling fan is provided by the

Level Sensor" are programmed to match the old

ECM in order to control the cooling fan. An input

ECM. Check the test ECM by measuring the

from one of the following items may cause the fan

voltage at the breakout T from terminal 26 to

to turn ON:

terminal 5 again. If the problem is resolved with

the test ECM, reconnect the suspect ECM. If the

A/C compressor clutch

problem returns with the suspect ECM, replace

the ECM.

Engine coolant temperature sensor

STOP.

Air inlet temperature sensor

i01857652

Exhaust brake

Cooling Fan Circuit and A/C

PTO on/off switch

Compressor Clutch Circuit -

OEM installed A/C high pressure switch

Test

Manual fan override switch

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

The output for the cooling fan is intended to connect

System Operation Description:

directly to the circuit for the cooling fan solenoid.

Program the "Fan Control Type" parameter to

Use this procedure under the following situation:

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

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

Use this procedure to determine if the circuit for the

the fan will remain on for a minimum of 30 seconds

A/C compressor clutch is operating correctly. This

except for the following conditions:

circuit can be connected to J1/P1:41 Input #11 or

to J1/P1:62 Input #12.

Engine start-up

Note: Not all vehicle manufacturers, or all trucks

The "A/C Pressure Switch Fan On Time" is

for a manufacturer use the Caterpillar cooling fan

programmed to less than 30 seconds.

circuit. Prior to troubleshooting, determine if the

vehicle is using the ECM cooling fan circuit.

During engine start-up, the ECM will keep the fan

on for two seconds after the engine has reached

Check the following items in order to determine if a

the programmed low idle (700 to 800 rpm). The fan

vehicle is using the ECM cooling fan circuit:

will be on continuously if the electrical circuit to the

cooling fan solenoid has an open circuit or if the

The "Fan Control Type" parameter must be

circuit for the ECM cooling fan relay has an open

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

circuit.

speed options. The Caterpillar factory default is

None.

Cooling Fan ON Conditions

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

The ECM will turn on the cooling fan under any of

second and 600 seconds.

the following circumstances if engine speed is less

than 2750 rpm:

A wire is present in the ECM vehicle harness

connector J1/P1 (terminal 11) which is Output #5

The engine is not running.

(cooling fan solenoid).

Engine cranking

Perform the special test for the "On/Off Cooling

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

The coolant temperature is greater than 96 C

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

(205 F).

Test". Activating and then deactivating the circuit

should cause the solenoid to click if the circuit is

Active diagnostic code for the coolant temperature

working properly.

sensor

The following background information is related

The inlet manifold air temperature is greater than

to this procedure:

87 C (189 F).