F 350 4WD Super Duty V8-6.4L DSL Turbo (2008)
Radiator Cooling Fan Speed Sensor: Description and Operation
FAN SPEED SENSOR (FSS)
The FSS is a Hall effect sensor integral to the cooling fan. The PCM monitors the sensor input and controls the cooling fan speed based upon the engine
coolant temperature (ECT), the transmission fluid temperature, and the intake air temperature (IAT) requirements. When an increase in cooling fan speed
for vehicle cooling is requested, the PCM monitors the FSS signal and outputs the required pulse width modulation (PWM) signal to a fluid port valve
within the cooling fan.
