Cooling System: Description and Operation

A Variable Control Relay Module (VCRM) is used to control engine cooling fan operation speed and A/C clutch operation in addition to other non-A/C functions. The VCRM will increase and decrease fan speed as necessary, depending on refrigerant system high side pressure. It also can turn the A/C clutch circuit OFF if high side pressure exceeds 425 psi. It will 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 high side pressure is above 300 psi. Fan control will not shut off when high side pressure is above 300 psi. In event of an high side pressure sensor failure, fan control will continue to operate.