‘20 Cyclone - Mid and Garage Thermostat no power?


Took unit out of storage (indoor) and sent right to dealer for seals and normal maintenance. Conducted Appliance check and it’s reported that the Mid and Rear Thermostats are not powering up. Dealer charged 1 hour of labor at 200$ to tell me the Capacitance Touch Dometic units have no power going to them and fuses are good.

So I am bringing it back and looking into it myself. At 200$ an hour, if that took them an hour this will be a multi thousand dollar bill to trace this down. I have a strong electrical background so I’m going it myself. Also, the front Bedroom Thermostat works fine, apparently.

— Anyone know what the 12v source is from the fuse box eventually to the Thermos? There must be a common place where both 12v sources for mid and aft are open. Can’t have two independent failures. They have to be tied. Does the 12v source power goto the furnace then to the AC units control boards, then to the Thermo on the wall, or does the 12v source go straight to the AC units?

Anyone know of any inline fuses along the way?

Any info you can share is appreciated.


Well-known member
I doubt if there are inline fuses. First Job would be to check wiring at thermostats for power, not trusting the dealer. Check fuses yourself by removing them and checking. I've had issues with the capacitive touch tstats to where I had to remove the spogy backing on the buttons to get it to work, but that was with power to it.


Update: So all three TStats are unpowered as are the vent fans. Both are combined on one 12v fuse. Fuse is good and power to the fuse is good. Clearly it’s upstream of the fuse but down line of where they branch off to the three TStats and two vent fans. Requesting schematic from Heartland.

Here’s an interesting unclear understanding. So if you read Dometic’s installation guide, it shows that 120v comes into the control box, and it outputs 12v as well as a data line (+, -, C) to the Tstat for that unit. My understand is that there is a transformer on board that converts 120AC to 12vdc low current for powering the TS. There is a twin line going to the furnace to trigger the furnace if the Tstat controls one. I can’t find a 12v input in any of their documentation.

It seems that maybe Heartland powers the +, - 12v to the TStats from the 12v system directly and just the one “C” wire goes to the control box for data.

I’m documenting this for anyone else downline who has a similar issue.


Well-known member
I have not ever seen any anywhere.

I just looked at our 12Vpanel and there is only a fuse for the furnace, nothing for the thermostats. So, I am wondering:
Is the power okay everywhere else in the rig? Could something happen to the incoming power leg that is adding to this, or the reason for the situation?


Thanks. The AC Power is good. They have the two vent roof fans and three AC Thermos on one DC circuit that is getting power as far as the fuse. Labeled as “AC/Vents”. I left it with the dealer. I went there and spent some time with the foreman today. I have good confidence in their next moves. I just wish they manufacturers would provide just some basic info to owners for wiring diagrams etc. for gods sake we pay six figures for a home on wheels and can’t access info about it.

I’m pretty confident it’s the run coming from the fuse panel and up the wall, prior to or at the splice or junction where they are tied together. Getting to it and locating it is the key if that’s the case.

All other AC and DC items work fine.

Hoping the factory will get the dealer some good tech info on locating it and how it’s wired.