Cooling Fan Control
WARNING: This page is about a different car, the 2003 Pontiac Sunfire and 2003 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.
The engine cooling fan system consists of 1 cooling fan and 1 relay. The relay is powered by the battery positive voltage circuit and controlled by a switched ground from the powertrain control module (PCM).
During operation, the PCM supplies the ground path for the cooling fan relay through the cooling fan relay control circuit. This energizes the cooling fan relay coil, closes the relay contacts, and supplies battery positive voltage from the cooling fan fuse through the cooling fan motor supply voltage circuit to the cooling fan. The cooling fan motor is grounded through its own ground circuit.
The PCM commands the fan ON under the following conditions:
- Engine coolant temperature exceeds approximately 106°C (223°F).
- A/C refrigerant pressure exceeds 1310 kPa (190 psi).
- A/C is requested and vehicle speed is below 100 km/h (62 mph) with A/C pressure above 1413 kPa (205 psi).
- Vehicle speed is less than 8 km/h (5 mph) for more than 750 seconds. The fan will turn OFF when vehicle speed is greater than 8 km/h (5 mph) for more than 20 seconds.