Fan Speed Sensor (FSS)
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2007 Ford RV Cutaway, 2007 Ford Pickup, 2007 Ford F550 Super Duty, 2007 Ford F450 Super Duty, and 2007 Ford Econoline. However, it is still accessible from the selected car via links, so may be relevant.
The FSS is a Hall effect sensor integral to the visctronic drive fan (VDF). The PCM monitors the sensor input and controls the VDF speed based upon the engine coolant temperature, the transmission fluid temperature, and the intake air temperature (IAT) requirements. When an increase in fan speed for vehicle cooling is requested, the PCM monitors the FSS signal and outputs the required PWM signal to a fluid port valve within the VDF.