Try this > Disconnect all the electrical from the camper/MH including turning off the batteries. Wait 10 to 15 minutes for it to reset and then try it. Had exactly the same problem in the wilderness of SD a while back. Guy was gonna charge me 125 dollars to come from Rapid City to look at it - and this was going to be the next PM before he arrived. Talked to another tech who was busy and could not show up until the next day. He suggested we do exactly what I said above and we had cool air in less than 30 minutes and at no cost. Love honest people!