Originally Posted by midocr
So....why would my fan be running almost constantly even though the air temps have cooled down to and below the freezing mark? Is there a sensor that controls the fans?
IIRC, the engine computer uses the coolant temperature sensor to determine when the fan kicks on. Above a certain coolant temperature, the fan runs continuously, regardless of ambient air temperature or A/C settings.
If your fan clutch is slipping, it's possible that the coolant temperature could get high enough to turn on the electric fan. This can even happen in cold weather, if the truck isn't being driven fast enough to force sufficient air through the radiator.