Dometic AC, Thermostat no power, where is 12v fuse?

[mileshuff]

Air conditioning stopped working on my last trip. LCD thermostat display is blank. It's not getting 12VDC. Thermostat has 3 wires going to control box thats mounted just above the filter grill.

In my trailers circuit box there is no 12V fuse for AC, only a breaker for 110V. I'm assuming that the air conditioner supplies the 12V for the controller and tstat and that there is a fuse somewhere.

Is fuse inside the grey control box thats mounted above the filter grill or perhaps up on the roof under the shroud somewhere?

TStat I have is similar to this one:

Dometic LCD Thermostat

[Rooted]

Did you ever find the solution? I have the same problem. 

[QCMan]

After ten years the OP is probably gone like most former members.

[Rooted]

Didn’t even notice the timestamp, just the title of a similar problem ha. 

[mileshuff]

Bobbo wrote:
Not to berate the obvious, but you DO have your house battery connected, right? If you use the battery disconnect switch, you lose the 12v to the thermostat as well as most everything else.

Yes, that would cause many other items to not function if running on battery. This is while fully hooked up, battery connected too.

[Bobbo]

Not to berate the obvious, but you DO have your house battery connected, right? If you use the battery disconnect switch, you lose the 12v to the thermostat as well as most everything else.

[mileshuff]

Chris Bryant wrote:
Normally, the 12 volt power for the A/C will feed from the furnace.

Looked into that and you are correct. Pulled the furnace cover off and there is a 12V circuit breaker that feeds the tstat. Reset that but still no display on the tstat. I did not have shore power hooked up but I would think thats not needed unless I want A/C. Tomorrow I'll get my volt meter out and do some more checking.

[Chris_Bryant]

Normally, the 12 volt power for the A/C will feed from the furnace.

[Old-Biscuit]

Deleted.....

[dougrainer]

There IS a 12 volt fuse in the 12 volt fuse section of your RV for the roof AC. The Roof AC does NOT convert the 120 volts to 12 volts. The 12 volt power is one of the small gauge wires at the roof AC control box and the 3 wires going to the wall tstat supply the power to the wall tstat. Doug

[time2roll]

The 12v feed does come from the grey box up in the ceiling however there is no fuse up there afaik. Good to go up there and check 12v power though.

I think the fuse will still be part of the stack near the converter. Just a likely to be a bad connection up near the grey box.

Good luck.