Electrical System

The fan control system consists of:
- Powertrain Control Module (PCM).
- Air Conditioning (A/C) pressure cut-off switch.
- High speed cooling Fan Control (FC) relay.
- Low speed cooling fan control (FC) relay.
- Engine cooling fan resistor.
- Engine cooling fan motor.

The powertrain control module (PCM) determines the cooling fan motor requirements and controls the fan operation through the low speed fan control and high speed fan control outputs. The PCM outputs complete the ground side of the relay coil circuits. Power to the relay coil circuits is provided by the PCM power relay.

If low speed fan operation is required, the PCM grounds the low speed fan control output. This energizes the low speed FC relay coil which closes the low speed FC relay contacts. Power flows through the fuse 2 (60A), the low speed FC relay contacts, the engine cooling fan resistor, and the engine cooling fan to ground. The engine cooling fan resistor provides thermal overload protection for the low speed fan control circuit.

If high speed fan operation is required the PCM grounds the high speed FC relay coil which closes the high speed FC relay contacts. Power flows through the fuse 2 (60A), the high speed FC relay contacts and the engine cooling fan to ground.

High speed fan operation may also be commanded by the dual pressure A/C pressure switch. The medium pressure contacts of the A/C pressure switch turn on the high speed cooling fan when A/C head pressure reaches a predetermined level grounding the air conditioning pressure switch. This grounds the high speed FC relay circuit. This closes the high speed FC relay contacts and turns on the high speed cooling fan.

If A/C head pressure drops below the predetermined level, the medium pressure contacts open returning the high speed FC relay operation to the PCM.