Radiator Cooling Fan Motor Relay: Description and Operation

Electric Cooling Fan Control Circuit:

Purpose:
The ECM controls the ground path for the cooling fan relay. The ECM determines operation based on various sensor inputs.

Operation:
The ECM will activate the primary cooling fan when any of the following conditions exist:

^ Certain ECM diagnostic trouble codes are set
^ Coolant temp is above 108°C (226°F)
^ A/C head pressure is above 248 psi

When the primary fan has been turned "ON" by the Engine Coolant Temperature (ECT) Sensor the ECM will turn the fan "OFF" when that temperature has dropped about 3°C (5°F). If the fan was turned "ON" by high A/C head pressure, the ECM will turn the fan "OFF" when the pressure has dropped to 200 psi. The minimum run time for the primary cooling fan is 50 seconds.

Location:
The primary cooling fan relay is located in the underhood electrical center.