Radiator Cooling Fan Motor Relay: Description and Operation
RADIATOR FAN RELAYDESCRIPTION
The HI/LO and HI radiator fan relays are located in the Power Distribution Center (PDC) near the coolant recovery pressure container. A decal on the inside of the PDC covers shows the location of each relay and fuse contained in the PDC. It is an ISO relay.
All vehicles (except 2.7L base) are also equipped with No. 1 and No. 2 radiator fan relays that are mounted to the radiator fan motor shroud.
OPERATION
2.7L BASE
The cooling system uses two fans. Both fans operate at two different speeds, low and high. Depending on engine coolant temperature and A/C system high side pressure, the fans operate at either low or high speed. The PCM controls radiator fan speed by grounding the coil side of either the HI/LO fan relay or the HI fan relay. The ignition switch supplies voltage to the coil sides of the relay. When the PCM grounds the coil side of the relay, the contacts close and the battery supplies power to the fans. Refer to WIRING DIAGRAMS.
EXCEPT 2.7L BASE
The cooling system uses two fans. Both fans operate at two different speeds, low and high. Depending on engine coolant temperature and A/C system high side pressure, the fans operate at either low or high speed. The PCM controls radiator fan speed by grounding the coil side of either the HI/LO fan relay or the HI fan relay. Low speed radiator fan function is achieved by running both fan motors in a series circuit. High speed radiator fan function is achieved by running both fan motors in a parallel circuit. Refer to WIRING DIAGRAMS.