Cooling Fan

On many models, PCM regulates operation of electric cooling fan through a PCM-controlled relay which controls the ground circuit or power circuit for the cooling fan. This allows PCM to operate cooling fan based upon engine temperature.

Most systems will engage electric cooling fan whenever A/C clutch is engaged, regardless of engine temperature. As a back-up system, many models use a coolant override switch that will also engage the cooling fan if PCM fails to energize the cooling fan relay or the cooling fan relay malfunctions. A malfunction of the cooling fan will cause engine overheating and possible detonation.

Some models use more than one cooling fan. The second fan may function as an auxiliary cooling device when A/C is engaged or (on models using refrigerant temperature sensors or high pressure switches) during periods of engine overheating or high A/C refrigerant pressures.

For component application and related wiring, see wiring schematics under MISCELLANEOUS CONTROLS in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE section below.

• SYSTEM/COMPONENT TESTS - 4.3L
• SYSTEM/COMPONENT TESTS - 5.7L