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 Engine Control Module (ECM). The ECM receives input signals from the Coolant Temperature Sensor (CTS), the Vehicle Speed Sensor, and the A/C Mode Selector. The ECM activates the Coolant Fan Relay when: (1) the engine coolant temperature, which is sensed by the Coolant Temperature Sensor, is above 108°C (227°F); (2) when the air conditioning is turned on; (3) when the Coolant Temperature Sensor fails. Any of these input signals causes the ECM to ground circuit 335 when vehicle speed is less than 56 Km/h (35 mph). With circuit 335 grounded, the Coolant Fan Relay is energized and its contacts close, turning the Coolant Fan on.