Engine Cooling Fan: Operation

CAUTION: Disconnect the cooling fan prior to performing any underhood service. The fan could cycle if the ignition switch is left in the "ON" position even though the engine is not running.

The cooling fan is controlled by the Integrated Relay Controller Module (IRCM) and EEC-IV module, which will energize the cooling fan under the following conditions:

Engine temperature is higher than normal. Low-speed fan comes on at 215°F (102°C), and goes off at 210°F (99°C).
A/C is on and vehicle speed is below 43 MPH.
Cooling fan is turned on high speed if engine temperature is higher than desirable and fan has been operating at a low speed. Fan comes on at 230°F (110°C), and goes off at 224°F (107°C). During idle, cooling fan is turned on high fan speed at 236°F (113°C).
Cooling fan will turn off (providing engine coolant temperature is not too high) if driver demand is Wide Open Throttle (WOT) or A/C is not operating.

When A/C low side pressure is low, the clutch cycling pressure switch cuts off power to the ECA, which then interrupts the compressor and engine cooling fan operation, providing the engine coolant temperature does not call for fan operation.

Several different controllers are available depending on application. Proper operation of the system cannot be obtained unless the correct controller is used.