Cooling System: Description and Operation

How the Circuit Works

Condenser Fans

Battery voltage is supplied at all times through fuse 36 and the left condenser fan motor and also through fuse 37 and the right condenser fan motor to the normally open contacts of the condenser fan relay. With the ignition in ON (II), battery voltage is supplied through fuse 4 and the condenser fan relay coil to the fan control unit. When the control unit receives the condenser fan and A/C request from the climate control unit, it grounds the ORN/BLU wire and energizes the condenser fan relay. The relay contacts close, providing a ground for the condenser fan motors. The motors run to remove heat from refrigerant passing through the A/C condensers.

Radiator and Engine Compartment Fans

Battery voltage is supplied at all times through fuse 31 and the radiator fan motor to the normally open contacts of the radiator fan HIGH and LOW relays. Battery voltage is also supplied at all times through fuse 24 to the normally open contacts of the engine compartment fan relay. With the ignition switch in ON (II), battery voltage is supplied through fuse 4 and the radiator fan relay coils and through the engine compartment fan relay coil to the fan control unit. When the radiator sensor detects a coolant temperature above 183 °F (84 °C) it grounds the GRN/BLK wire to energize the radiator fan LOW relay. With the relay contacts closed, the radiator fan motor is grounded through the radiator fan resistor. The fan runs at low speed to remove heat from the coolant. When the radiator fan control sensor detects a coolant temperature above 194 °F (90 °C), it grounds the BLU/RED wire to energize the radiator fan HIGH relay and the engine compartment fan relay. With the relay contacts closed, the radiator fan motor is grounded and the radiator fan runs at high speed to remove heat from the coolant. The engine compartment fan relay also feeds battery voltage to the engine compartment fan which then runs to remove heat from the engine compartment.