No Power to Main Thermostat

[Poolguy]

I have a 2017 Heartland Bighorn 3970RD. Last weekend I pulled my RV out of storage to clean it up and get ready for the season.
Ran into 2 issues:
#1 Main thermostat has no power, which equals no heat and no AC.
#2 Fireplace in living room has no power

#1
I ran the heater in January when I stopped by to check up on my RV, no issues, ran for about 2 hours.
When I picked it up last weekend the thermostat had no power, I checked the fuses and breakers and all appear to be fine.
I even pulled the exterior cover off the heater to verify it had power going to it, and it did. Switch is turned on on the gas valve.
I removed the thermostat from the wall and swapped it with the second thermostat in the bedroom. main thermostat powered up when plugged into the bedroom and bedroom one did not power in the main location. So I ruled out faulty thermostat. I tried to trace the phone cable from main location and was able to trace it as far as heading down to the basement compartment where the heater and water heater are located.
So I'm at a loss where to go from here.

#2
Fireplace has no power, I checked the outlet and it is working fine.
it does not power on with the power button on front, nor the remote control.
I'm not sure if anyone has had this issue with their fireplace.

This all lead to a cold night at the lake, thank goodness I had plenty of blankets!

Thanks for any help on this.

 

[wdk450]

The thermostat uses 12 VDC, (trying to measure a DC voltage with your DVM set on volts AC won't measure anything on a DC circuit) pulling the desired HVAC function wire to ground. Is there an indicator glowing on your 12 VDC fusepanel, indicating a blown fuse? Does the ground wire on the thermostat show continuity to a frame ground?

The HVAC wiring supplies the +12 VDC for the thermostat to the Air Conditioner control board. This sent on to the thermostat with the Fan wires, the Heat wire and the Cool wire. Grounding any of these wires at the thermostat turns on a relay to activate the function. This board also sends controlling signals to the heater.

 

[Poolguy]

The thermostat uses 12 VDC, (trying to measure a DC voltage with your DVM set on volts AC won't measure anything on a DC circuit) pulling the desired HVAC function wire to ground. Is there an indicator glowing on your 12 VDC fusepanel, indicating a blown fuse? Does the ground wire on the thermostat show continuity to a frame ground?

The HVAC wiring supplies the +12 VDC for the thermostat to the Air Conditioner control board. This sent on to the thermostat with the Fan wires, the Heat wire and the Cool wire. Grounding any of these wires at the thermostat turns on a relay to activate the function. This board also sends controlling signals to the heater.

Thanks for the response.
Unfortunately my RV uses the Dometic multizone thermostat, which uses a phone cord to a controller box (which I have yet to locate) and Heartland service response was take to a service center to have it repaired. Honestly I would have preferred it to have standard wiring, and there is standard wire installed in the wall, but not hooked up.

So, at this point I'm still at guessing where the controller for the Dometic is located. My next place to check in on the roof inside the AC unit.

 

[dieseldog]

The controller is located in the front of the ac unit along with the 12volt and RJ11 4 contact telephone cord data cable. You’ll have to remove the shroud on the air conditioning unit to access those. Sounds like you’ve lost power up top, the controller went bad or your data cable has issues. Mine did the same and it was a bad data cable.

 

[Poolguy]

The controller is located in the front of the ac unit along with the 12volt and RJ11 4 contact telephone cord data cable. You’ll have to remove the shroud on the air conditioning unit to access those. Sounds like you’ve lost power up top, the controller went bad or your data cable has issues. Mine did the same and it was a bad data cable.

Thanks!
I'm guessing data cable, since the bedroom ac is still working.
Is it in the front unit or the rear unit?

 

[dieseldog]

If they’re blizzard units which I suspect they are as I have the same model unit, remove the shroud over the unit, then remove the upper cover over the evaporator and blower. All your wiring will then be exposed. You can check to verify 12v power is supplied to the controller and your getting 120v as well. For the data cable I found an old female plug with some wire and was able to check continuity on it. The green wire had a break in it somewhere so I ran new data cable and got it repaired. Check all your connections first before all else though! Almost forgot...if the thermostat in the living area isn’t working, you’ll need to look at the unit at the rear of your 3970.

 

[Poolguy]

If they’re blizzard units which I suspect they are as I have the same model unit, remove the shroud over the unit, then remove the upper cover over the evaporator and blower. All your wiring will then be exposed. You can check to verify 12v power is supplied to the controller and your getting 120v as well. For the data cable I found an old female plug with some wire and was able to check continuity on it. The green wire had a break in it somewhere so I ran new data cable and got it repaired. Check all your connections first before all else though! Almost forgot...if the thermostat in the living area isn’t working, you’ll need to look at the unit at the rear of your 3970.

Thanks again!
You've given me a better answer than both Heartland & Dometic!
I'll update the tread when I'm able to get up there and take a look

 

[dieseldog]

Your very welcome. Just work your way through the connections. Now is a good time to invest in a quality voltage tester if you don’t have one. Work your way from the unit all the way back to the fuse panel. The thermostat worked on the bedroom ac after you swapped so you can rule that out.

 

[wdk450]

You might try some Caig DeOxIt contact cleaner/restorer spray on every set of contacts you encounter.

http://store.caig.com/core/media/me...T113328&h=d15a4569f3d6c7c85aba&whence=http://