Radiator Cooling Fan Control Module: Description and Operation

The variable control relay module (VCRM) is used to control the engine cooling fan operation speed and A/C clutch operation in addition to other non-A/C functions. The VCRM control fan operation when required will increase and decrease fan speed as necessary depending on refrigerant system high side pressure. The VCRM also can turn the A/C clutch circuit off if the high side pressure exceeds 425 psi. The VCRM is connected electrically to the powertrain control module (PCM), with the A/C high side pressure (ACP) sensor, A/C clutch coil circuit and the fan control circuit.
Another feature of the VCRM is the ability to stop fan control operation at vehicle speeds in excess of approximately 45 mph. Fan operation will resume when vehicle speed drops approximately 42 mph. One exception is when the high side pressure is above 300 psi. The fan control will not shut off when the high side pressure is above 300 psi. In the event of an ACP sensor failure, the fan control will continue to operate.