GUIDE 1076878 - Caterpillar

System Operation Description:Use this procedure under the following situation:Use this procedure to determine if the cooling fan (output 5) or the A/C high pressure switch (input 11) is operating correctly.Note: Not all vehicle manufacturers, or all trucks for a manufacturer use the Caterpillar cooling fan circuit. Prior to troubleshooting, determine if the vehicle is using the ECM cooling fan circuit.Check the following items in order to determine if a vehicle is using the ECM cooling fan circuit:
The "Fan Control Type" parameter must be programmed to "On/Off" or one of the variable speed options. The Caterpillar factory default is None.
"A/C Fan On Time" is programmed between one second and 600 seconds.
A wire is present in the ECM vehicle harness connector J1/P1 (terminal 11) which is output 5 (cooling fan solenoid). This occurs if an On/Off type of fan is used.
Perform the Special Test for the "On/Off Cooling Fan". Access each menu in the order that follows: "Diagnostics", "Diagnostic Tests" and "Special Test". Activating and then deactivating the circuit should cause the air solenoid to click if the circuit is working properly.The following background information is related to this procedure:Cooling FanThe signal for the cooling fan is provided by the ECM in order to control the cooling fan. An input from one of the following items may cause the fan to turn ON:
Engine coolant temperature sensor
Air inlet temperature sensor
Exhaust brake
PTO on/off switch
OEM installed A/C high pressure switch
Manual fan override switchA control unit for the A/C may be connected to the A/C high pressure switch (input 11) instead of a switch. The output for the cooling fan is intended to connect directly to the circuit for the cooling fan solenoid. 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:
Engine start-up
The "A/C Pressure Switch Fan On Time" is programmed to less than 30 seconds.During engine start-up, the ECM will keep the fan ON for two seconds after the engine has reached the programmed low idle (700 to 800 rpm). The fan will be ON continuously if the electrical circuit to the cooling fan air solenoid valve has an open circuit or if the ECM Fan Relay circuit is opened.Cooling Fan ON ConditionsThe ECM will turn the cooling fan ON under any of the following circumstances if engine speed is less than 2750 rpm:
The engine is not running.
Engine cranking
The coolant temperature is greater than 96 °C (205 °F).
Active diagnostic code for the coolant temperature sensor
The inlet manifold air temperature is greater than 87 °C (189 °F).
The inlet manifold air temperature is greater than 72 °C (162 °F) while the boost pressure is greater than 70 kPa (10 psi).
The manual fan override switch is on.
The "Fan with Exhaust Brake ON" is programmed to "YES" and the exhaust brake has been on at least two seconds.
The "A/C Switch Fan On-Time" is programmed