Electric Fan

Electric cooling fan is now controlled by the PCM. PCM uses a remote power output final stage mounted on fan housing. The power output stage receives power from a 50-amp fuse (located in glove box above fuse bracket). Electric fan is controlled by a pulse width modulated signal from the PCM. The fan is activated based on the PCM calculation (sensing ratio) of coolant outlet temperature, calculated (by the PCM) catalyst temperature, vehicle speed, battery voltage, and air conditioning pressure.

When vehicle is first started the fan is activated briefly (20 percent of maximum speed), then it is switched off. This procedure is performed for diagnostic purposes. If PCM indicates a fault, check fan for freedom of movement. After initial test has been performed, fan is brought up to specified operating speed. At 10 percent (sensing ratio) fan runs at 1/3 speed. At a sensing ratio of between 90-95 percent the fan is running at maximum speed. Below 10 percent or above 95 percent the fan is stationary. When A/C is switched on, the electric fan is not immediately activated. After the engine is switched off, the fan may continue to operate at varying speeds (based on the PCM calculated catalyst temperature).