Visctronic Drive Fan Clutch

WARNING: This page does not describe the selected car, but rather 32 other vehicles, including the 2002 Mercury Sable, 2002 Mercury Mountaineer, 2002 Mercury Grand Marquis, 2002 Mercury Cougar, and 2002 Lincoln Town Car. However, it is still accessible from the selected car via links, so may be relevant.

The primary purpose for Visctronic Drive Fan (VDF) clutch is to optimize fan energy (i.e. improved fuel economy) while meeting cooling performance requirements. Successful optimization will also minimize objectionable fan noise. Operation is similar to existing viscous fan clutches, except viscous fluid flow is controlled by a Pulse Width Modulated (PWM) solenoid versus a bi-metal temperature sensor on the front of the clutch. VDF consists of 3 main elements; a working chamber, a reservoir chamber, and a Fan Speed Sensor (FANSS). A fluid port valve controls fluid flow from the reservoir into the working chamber. Once viscous fluid is in the working chamber, "shearing" of fan clutch fluid will result in fan rotation.

The valve is activated via a PWM output signal from PCM. By opening and closing the fluid port valve, PCM can control approximate fan speed. Fan speed is monitored via a Hall Effect sensor and is read by PCM for closed loop operation. PCM will optimize VDF fan speed based upon Cylinder Head Temperature (CHT), Transmission Fluid Temperature (TFT), or Intake Air Temperature (IAT) sensor cooling requirements. When either of these inputs is demanding increased fan speed for vehicle cooling, PCM will monitor FANSS, and output required PWM signal to fluid port valve to control fan speed.