AC electrical problem Help

[TheGoslins]

We have a 1994 Fleetwood Pace Arrow that suddenly developed electrical issues with the AC unites & the new thermostat that we replaced a year ago. We are looking for some trouble shooting help everything we've tried so far is not working. It started with rear AC unit not getting any power so my husband used the earth ground wire to get power after consulting with a local RV repair shop. It is working, but now we have an issue with the front AC unit lost 12 volt power to new thermostat. So we ran new wiring to the thermostat & it was working. Then it quit, in the process of trying to check it I turned the thermostat down to see if it would kick on after a few seconds nothing so I turned it off AC and tried just switching to fan nothing then I turned it off then tried again to go to fan but switch went past AC, Fan, to heat which caused sparks to fly needless to say scaring me. Since then we have checked all the wiring on the thermostat bought another new one but before putting it on we managed to get the fan to come on but the high fan relay was chattering and got hot so we found one and bought it but the new relay is doing the same thing even with the new thermostat.

[Rkesselus]

Not real sure what you are calling an earth ground wire. If you are refering to the 120 volt Ac wire you would have a hot (black or red) a common (white) and a ground (either green or bare copper). The Hot and Common would be connected to wires on the air conditioner wires and the ground attached to a metal part of the unit. Here is what I would do but only if you are familiar with a voltage meter. Start at the transfer with and see if you are getting power to the switch. You should have two hots from a 50 amp shore power source. If you have power at the transfer switch go to the electric panel in the coach. It is the converter and will have a 12 DC volt buss bar with fuses and you will have 4 120 volt AC breakers. See if you have voltage there. If so two of the breakers will power the AC units. Trace the wires to the AC and make sure you have 120 volts at the AC. If so then check the thermostat 12 v service wire. If you have voltage there all should be good. From what you describe it sounds like you have a short issue somewhere along the line and you should have discovered it if you did the above procedure. If you got the wires on the thermostat switched when you installed the new one. That could be a problem as well. There should have been a diagram with the thermostat and you should find the color code there. AC thermostte are pretty universal with color code wires and what they do.

[veraken]

We had ours replaced with a new Dometic CCC2 unit. When we did, we had problem. The thermostat is mounted on an outside wall and there is a small cavity behind the thermostat where the wires are run. The high temp in the wall meeting the cool air inside, created condensation on the thermostat's PC board which caused it to short out. To solve this I used low expansion spray foam in the wall and sheet foam on the back of the PC board. So far, everything is fine. If not I will have to relocate thermostat to an interior wall.

You didn't state which thermostat you installed, but this may give you an idea.