[Diesel_Dave]

I have a clutched fan on my truck. I believe the clutch is electrically controlled. I'm thinking I may be able to improve my FE by turning it off when it's not needed. An electricl fan is an option, however, if the clutch is electricallly controlled, I should be able to just use that to control the fan better (which should be more efficient than an electric fan). Before I do anything, however, I want the check and see how often the fan is running "unnecessarily" as it currently is.

It's a pretty quiet fan, so I can't hear it over the engine. Does anybody have any tips for a quick and dirty way to tell if the fan is running (while driving)?