Radiator Cooling Fan Motor Relay: Description and Operation

Coolant Fan Circuit:

Purpose:
All front wheel drive vehicles with transversely mounted engines, and some other vehicles, use electric cooling fans. The fans are used for engine and A/C condenser cooling but only operate under certain conditions.

Operation:
Electronic cooling fans operate when engine coolant temperature exceeds a certain value. The PCM completes the ground paths for the windings of the cooling fan relays. The relay contacts then close and complete the circuit between the 60 amp maxifuse and the fan motor. When the engine cools down, the PCM removes the ground for the fan relays and the fans stop.

The PCM will complete the ground path for the winding of the low speed fan when it sees engine temperature above 100°C (212°F) or when A/C is requested. The fans will continue to run for approximately 45 seconds after the A/C request signal is gone.

The A/C head pressure switch signals the PCM to turn "ON" the high speed fan relay when A/C pressure exceeds 210 psi (1448 kPa). It also turns "ON" when engine coolant temperature is above 108°C (226°F). There is a six second delay for high speed fan to turn "ON" when low speed fans are "ON".

Location:
The cooling fan relays are located in the left hand underhood fuse block.