The engine cooling fans for 4.5L, 6.0L, 6.4L and 6.7L Power Strokes is an electro-viscous design. The engine cooling fan clutch is electronically controlled by the PCM, based on input information received from various engine sensors. The PCM provides a Pulse Width Modulated (PWM) signal to the fan clutch and monitors fan speed through the Fan Speed Sensor (FSS). Common controlling factors might include engine oil temperature, transmission oil temperature, coolant temperature, AC system pressures and ambient air temperature.
