Radiator Cooling Fan Motor Relay: Description and Operation

Cooling Fan Circuit:

Quad-Driver Module (QDM 2) Circuit:

PURPOSE:
The electric Cooling Fans are used for engine and A/C condenser cooling and are controlled by the PCM.

The PCM provides the ground for the coils within the cooling fan relays. As the ground is completed, the magnetic field generated closes the switch in the relay allowing current flow to the cooling fan motors.


OPERATION:

Primary Fan - will be turned "ON" by any of the following criteria:

^ Engine coolant temperature (ECT) sensor signal indicating a temperature greater than 106°C (226°F)
^ A/C is requested at any vehicle speed
^ A/C pressure sensor switch is "open", pressure greater than 200 psi.
^ When PCM is in backup mode

Auxiliary Fan - will be turned "ON" with any of the following criteria:

^ Engine coolant temperature (ECT) sensor signal indicating a temperature greater than 123°C (253°F) and A/C "OFF".
^ A/C is requested and vehicle speed less than 40 mph
^ A/C pressure sensor switch is "open", pressure greater than 200 psi