Thread: added UD pulley's, need to change anything?
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Old Mon, June 15th, 2009, 03:16 PM
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Originally Posted by Sburn View Post
Ford changed stuff on the engine fans, starting ~2006 or 2007. Even though the fan is driven by the water pump pulley as before, the clutch is controlled by the PCM. And it appears to be more than just on/off control. Looks like the PCM outputs PWM (pulse-width moulation) which controls how much the clutch locks up, which in turn controls the actual speed of the fan. It's a closed loop system because the fan then has a sensor that reports its RPM back to the PCM. There's DTCs for when the PCM commands the fan clutch to engage and but doesn't see an increase in the reported fan speed.
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