Signal Functions

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The VDF is an electrically actuated viscous clutch that consists of 3 main elements:

a working chamber
a reservoir chamber
an actuator (electromechanical valve and speed sensor)

The actuator valve controls the fluid flow from the reservoir into the working chamber. Once viscous fluid is in the working chamber, shearing of the fluid results in fan rotation. The valve is activated via a pulse width module (PWM) output signal from the powertrain control module (PCM). By opening and closing the fluid port valve, the PCM can control the fan speed. Fan speed is measured through a Hall effect sensor, and is monitored by the PCM during closed loop operation.

The PCM optimizes the fan speed based on the engine coolant temperature (ECT), engine oil temperature (EOT), transmission fluid temperature (TFT), intake air temperature (IAT), or air conditioning requirements. When an increased demand for fan speed is requested for vehicle cooling, the PCM monitors the fan speed through the Hall effect sensor. If a fan speed increase is required, the PCM outputs the PWM signal to the fluid port, providing the required fan speed increase.