Electric Fans

An auxiliary electric fan is used on Cherokee, Comanche and Wagoneer models with a 4.0L engine, A/C and/or heavy duty cooling system. The auxiliary fan is controlled by a relay mounted on the left inner fender panel. Engine coolant temperature is sensed by a radiator temperature switch attached to radiator outlet tank, above lower radiator hose.

When coolant temperature is more than 190°F (88°C), radiator coolant temperature switch closes to allow current to from ignition switch to flow through fan relay to ground, activating relay. When relay is activated, battery voltage is supplied to fan causing it to operate. When coolant temperature is below 190°F (88°C), radiator coolant temperature switch opens to prevent relay from being grounded and electric cooling fan from being energized.

When A/C (if equipped) is turned on, the Electronic Control Unit (ECU) grounds A/C relay coil, allowing current to flow through relay coil. This activates the A/C relay, which then supplies current to the A/C clutch, fan diode assembly and cooling fan relay, causing cooling fan relay to activate and operate fan. Whenever the A/C is used, the auxiliary electric cooling fan will operate regardless of engine coolant temperature.