Radiator Cooling Fan Motor: Description and Operation

The coolant fan is controlled by the coolant fan relay. The coolant fan relay is electrically operated by the ECM. The ECM receives input signal from the coolant temperature sensor and the A/C mode selector. The ECM activates the coolant fan relay when engine coolant, which is sensed by the coolant temperature sensor, is above 227°F, when A/C is turned on and when coolant temperature sensor fails. Any of these input signals causes the ECM to ground circuit 335. With circuit 335 grounded, the coolant fan relay is energized and its contacts close. The battery runs with battery voltage across its terminals.