I've noticed recently that every once in a while, even though I'd turn off the AC system, my car would continue to make the AC whine...

Anyways, I just came back from a long car trip and I noticed my MPG was much lower than expected, and that I think that there was a little of the whine all the way back (Not sure though... spent most of it listening to loud music). Thus, I think my AC compressor clutch might be stuck... any troubleshooting hints or tips before I start digging through my Helms?