Cooling Fan Operation

Cooling Fan Operation

V8 Engine

The engine coolant temperature sensor sends an input on a G wire to pin C0636-22 on the ECM. The engine coolant temperature sensor is earthed on a RB wire to pin C0636-21 on the ECM.

When the coolant temperature is high, the value of input from the coolant temperature sensor causes the ECM logic to switch on the earth path for the coil of the cooling relay, on a GW wire to pin C0636-31 on the ECM. With the coil of the cooling relay earthed the coil is now energised. The cooling relay contacts close and current flows on a BN wire to the cooling fan motor.

All Models

The current flows through the cooling fan motor to earth header C0018 on a B wire The cooling fan motor will operate as long as the ECM receives a high signal input from the coolant temperature sensor. When the coolant temperature is low the ECM logic interrupts the earth path to the coil of the cooling relay. The contacts of the cooling fan relay open, the fan motor power supply is now broken and the motor stops. The cooling fan will cycle on and off as the coolant temperature rises and falls.