Air Conditioning problems w/2002 Durango

I've tested the wiring going to the air conditioning unit, the ground wire is testing with voltage coming back to it? Strange I know. Anyways, I was wondering if any of my fellow readers had (or knew of) a wiring diagram they could send me? Any other thoughts and ideas of what I can do?? The air cuts on and off with seemingly no reasoning. Usually, on the open road it's fine and will cut (and stay on) but in city, air does not cut on as it should. I really want to get this fixed before next summer. Thanks