In MY experience the clutch will lock, and the truck will not warm, and the belt will "chirp" on shut down. To check it, with the truck cold (and shut down!) try to spin the fan (it should be easy). Then after driving and reaching operating temp (180-190 degrees) shut down and try to spin the fan again, if the clutch is working properly, it should be tough to spin it.
Again, this is from MY experience and thoughts on how the stock fan works, you should consult a service manual. (I would check mine but I don't have it here at school)