The engine cooling fan system consists of one cooling fan and two relays. The cooling fan has 2 windings in the motor, one winding is for low speed and the other winding is for high speed. Voltage is supplied to the relays through the 30 A cool/fan 1 and 30 A cool/fan 2 fuses. The engine control module (ECM) controls the low speed fan operation by grounding the cool/an 1 relay control circuit. When the cool/fan 1 relay, which is the low speed relay, is energized, voltage is delivered to the cooling fan low speed winding. The ECM controls the high speed fan operation by grounding the cool/fan 2 relay, which is the high speed relay, control circuit. When the cool/fan 2 relay is energized, voltage is delivered to the cooling fan high speed winding. The cooling fan motor is grounded through its own ground circuit.

When the request for fan activation is withdrawn, the fan may not turn OFF until the ignition switch is moved to the OFF position or the vehicle speed exceeds approximately 10 mph. This is to prevent a fan from cycling ON and OFF excessively at idle.

The low speed cooling fan supply voltage circuit passes through a single 0.3 ohms cooling fan motor resistor. The resistor assembly is serviceable.

The engine cooling fan system consists of 2 electrical cooling fans and 3 fan relays. The relays are arranged in a series/parallel configuration that allows the engine control module (ECM) to operate both fans together at low or high speeds. The cooling fans and fan relays receive battery positive voltage from the underhood junction block.

During low speed operation, the ECM supplies the ground path for the low speed fan relay, which is cool/fan 1, through the low speed cooling fan relay control circuit. This energizes the cool/fan 1 relay coil, closes the relay contacts, and supplies battery positive voltage from the cool/fan 1 fuse through the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left cooling fan is through the cool/fan ser/par relay and the right cooling fan. The result is a series circuit with both fans running at low speed.

During high speed operation the ECM supplies the ground path for the cool/fan 1 relay through the low speed cooling fan relay control circuit. After a 3 second delay, the ECM supplies a ground path for the cool/fan 2 relay, which is the high speed relay, and the cool/fan ser/par relay through the high speed cooling fan relay control circuit. This energizes the cool/fan ser/par relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time the cool/fan 2 relay coil is energized closing the relay contacts and provides battery positive voltage from the cool/fan 2 fuse on the cooling fan motor supply voltage circuit to the right cooling fan. During high speed fan operation, both engine cooling fans have their own ground path. The result is a parallel circuit with both fans running at high speed.

When the request for fan activation is withdrawn, the fan may not turn OFF until the ignition switch is moved to the OFF position or the vehicle speed exceeds approximately 10 mph. This is to prevent a fan from cycling ON and OFF excessively at idle.