Cooling Fan

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

Most systems will engage the electric cooling fan whenever the 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 the ECM 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 freon temperature sensors or high pressure switches) during periods of engine overheating or high A/C freon pressures.

For component application and related wiring, see wiring schematics under MISCELLANEOUS CONTROLS in appropriate I - SYS/COMP TESTS article in this section.