RV Repair: R.v. Ac compressor not engaging, ground lead, 5th wheel

Question
Hello,
I have a 2005 Prowler 5th wheel with ac on roof and the compressor does not seem to be engaing. I tested it with voltage meter and in does not read anything except if i take ground lead of tester and ground out on frame of unit then it reads 3 volts on all wires encluding ground wire. If I ground to black wire on compressor it reads nothing. Any information would be very helpful.
Thanks Shawn

Answer
This is something that is pretty dangerous. I would say if you have no voltage then you curcit board is bad.Do you have 12 volt at the ac controler is this ducted or is this roof controls what model and make is it. Get this info and I can sget you some trouble shooting pages