This morning I hopped into my car after warming it up and drove to work. All was fine until I exited the expressway, and I noticed I had no power steering. I pulled over, opened the hood, and saw that the power steering pump wasn't spinning. The belt from the pump goes to the AC compressor, which has a double pulley. The outer pulley of the compressor which is belted to the water pump was spinning fine, but the inner pulley to the steering pump wasn't moving. No screeching, just didn't seem to be engaged. I continued on to work trying to figure out what was going on. I took a look at the rheostat for the AC and noticed it was on. I turned it completely counter-clockwise to turn of the AC and the power steering returned. Anybody got any ideas what's going on. Am I in for a compressor change, pulley change, of maybe just some bad wiring?

Thanks for any help.