Theory Of Operation
WARNING: This page is about a different car, the 2012 RAM Pickup. However, it is still accessible from the selected car via links, so may be relevant.
The cooling fan is a hydro-electric controlled device that is engine mounted. The Powertrain Control Module (PCM) monitors various sensors to control fan speed. The cooling fan provides temperature control for engine coolant, engine charged air, A/C Freon and automatic transmission fluid. Fan speed increases as cooling requirements increase. Since the fan is mounted to the engine, fan speed is related to engine speed (RPM). The PCM uses a Pulse Width Modulated (PWM) driver to control the amount of fluid to the clutch fan. When the fan is fully engaged it is capable of speeds about 10% greater than engine speed. The fan will rotate anytime the engine is running, even when the PCM is not sending a PWM signal.