Electric Cooling Fan

WARNING: This page is about a different car, the 2003 Pontiac Sunfire, 2003 Pontiac Grand Am, 2003 Oldsmobile Alero, 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 two electrical cooling fans and three fan relays. The relays are arranged in a series/parallel configuration that allows the Powertrain Control Module (PCM) 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. The ground path is provided at G103.

During low speed operation, the PCM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. This energizes the cooling fan 1 relay coil, closes the relay contacts, and supplies positive battery 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 cooling fan Mode relay and the right cooling fan. The result is a series circuit with both fans running at low speed.

During high speed operation the PCM supplies the ground path for the cooling fan 1 relay through the low speed cooling fan relay control circuit. After a 3 second delay, the PCM supplies a ground path for the cooling fan 2 relay and the cooling fan Mode relay through the high speed cooling fan relay control circuit. This energizes the cooling fan Mode relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time the cooling 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 there own ground path. The result is a parallel circuit with both fans running at high speed.

The PCM commands Low Speed Fans ON under the following conditions:

The engine coolant temperature exceeds approximately 223°F (106°C).
The A/C refrigerant pressure exceeds 190 psi (1310 kPa).
The vehicle is shut off when the engine coolant temperature is greater than 284°F (140°C) and system voltage is more than 12 volts. The fans will stay ON for approximately 3 minutes.

The PCM commands High Speed Fans on under the following conditions:

The engine coolant temperature reaches 230°F (110°C).
The A/C refrigerant pressure exceeds 240 psi (1655 kPa).
When certain DTCs set.

For component application, see appropriate ELECTRIC COOLING FANS article in ENGINE COOLING. For related wiring, see COOLING FAN in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.