2015 Thor Axis 24.1 Top Roof AC Thermostat Fuse Blows

[DLL66]

The fuse in my thermostat blows when I switch the A/C on. Last week, I had the thermostat replaced because when switching it to the fan, the fuse blow. After replacing the thermostat, the A/C worked perfectly. Today, I went to turn on the A/C and blew the thermostat fuse again. It doesn't blow when I turn the fan on, just when I switch it to A/C.


Any thoughts or experienced on with this? Going to be using it this weekend.

[Long & Winding road]

I would check behind the thermostat first for loose wires in the wall (or perhaps you have a defective thermostat?). My AC didnt have a Low speed for the fan but I found the wire beind the thermostat was disconnected. Perhaps the AC wire is shorting out right beind the Thermostat? Next take the cover off (on the inside) and look for a loose wires?

I dont know anything about AC systems but I would look for loose wires before I brought mine in to be serviced.

Hopefully someone else can chime in that had this same problem.

[javelin]

Usually the call for cooling by the thermostat puts +12v onto the Y lead (at the thermostat) which in turn closes a relay (probably located in or near the low voltage wiring section in the air conditioner) and that operates the compressor (connects 120VAC) in the air conditioner. Similarly the fan high speed GH and low speed GL air conditioning fan speed wires probably also control relays in the air conditioner that turn on the appropriate air conditioning fan motor speed. You already replaced the thermostat so while not impossible to have two bad units I would “suspect” ..... not the issue. Since you say the fuse blows only when the air conditioner compressor starts (not for the air conditioner fans) I would suspect that the Y wire up to the air conditioner is shorted to ground somewhere (perhaps intermitantly if it works sometimes and not others). Since there are lots of sharp metal edges around air conditioner units it might be possible that the Y wire has chafed against a metal part somewhere along its route that grounds that lead causing the short and thermostat fuse blow. It also might only occur randomly depending on motor vibration, coach motion etc. I think the air conditioning cable from the thermostat contains several control wires in the one cable up to the air conditioning unit so if the cable is cut it could affect any of the wires......so it could be a hard one to find. Also I am not sure if you can get access to these control wires in the inside ceiling space of the air conditioner or if it requires opening the air conditioner roof shroud to see where the control wires terminate (Y, GH, GL and B (ground)). Just my guess.

[DLL66]

Had a repair guy come out. After the repair guy calling Coleman, he suggested during the installation of the AC, that the wire could have been nicked by a screw or nail and it is finally just begun to short out. After rewiring, the AC is working like it suppose to.