Radiator Cooling Fan Motor: Description and Operation

Circuit Operation
With the ignition switch in ON or START, voltage is applied to the cooling fan relay. When the ECT sensor signals the Engine Control Module (ECM) that overheating has occurred, or if the A/C is turned ON, the ECM will apply ground to the cooling fan relay, energizing it. This relay then applies voltage to the fan motor, powering it until the coolant reaches the proper temperature or until the A/C cycles or is turned OFF.