[CraigH]

If the fan is running 90% of the time even in cooler temps the clutch is probably bad (or set wrong). I had this issue and my dealer replaced the clutch (2x)... second time was the charm. It will still cycle on and off a fair amount in warmer temps. If it is running all the time it amounts to a significant power drag.

My dealer advised there is also an option to convert to an electric fan which is controlled by a temperature sensor already present on the engine.

Good luck!