Cooling System: Description and Operation

Each Coolant Fan is turned on and off by a separate Coolant Fan Relay.

The Primary Coolant Fan Relay coil is grounded by the Engine Control Module (ECM) when vehicle speed is less than a speed determined by the ECM and the Engine coolant reaches 108°C (227°F) with A/C off or 106°C (223°F) with A/C on. The relay contacts close and voltage is applied through the Primary Coolant Fan Relay to the Primary Coolant Fan. The Primary Coolant Fan runs until the Ignition Switch is turned off, or Engine coolant temperature decreases to 104°C (220°F) with A/C off, or 102°C (216°F) with A/C on.

The Secondary Coolant Fan Relay coil is grounded by the ECM when the Engine coolant temperature reaches 118°C (245°F). The relay contacts close and voltage is applied to the Secondary Coolant Fan. The fan then runs at high speed and will continue to run at high speed with the Ignition in RUN" until the Engine coolant temperature lowers to 114°C (238°F).