Thermostat is blank

[CapnSteve59]

We took delivery on our new 2014 Silverado 35RES on Saturday and the furnace worked like a champ. On Sunday night the furnace stopped working and the thermostat is blank and unresponsive. I called the dealer, they say they've never seen this. They suggested I call Dometic and Dometic referred me to the "system initialization" sequence... no change. I've read posts here regarding bad mother boards, but curious if this would cause the thermostat to quit working. Any advice would be greatly appreciated.
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[danemayer]

Loss of 12V to the thermostat would also cause this failure. Are your interior lights working?

If you do have interior 12V lights working, take the cover off the thermostat and see if you have a broken or loose wire.

If all your 12V stuff is out, check our 12V Block Diagram and Diagnostic Guide for help.

 

[CapnSteve59]

I'm really a rookie at this, so bear with me. If I unplug our shore power and the lights still work, that would indicate 12 volt is working?

 

[danemayer]

I'm really a rookie at this, so bear with me. If I unplug our shore power and the lights still work, that would indicate 12 volt is working?

That's true, but you should also be getting 12V from your shore power, by way of the Power Converter. If you have 12V lights working while on shore power, you should also have 12V to the thermostat.

And of course, the 12V goes through the fuse box. You could have a blown fuse. If the circuit is ON, and the fuse is blown, the led next to the fuse should light to indicate a problem. But to really be sure, you might want to use an ohm meter to check fuses.

 

[CapnSteve59]

Thanks. Good to know on the lights. Everything else seems to be okay. I checked fuses first thing. Someone at the dealership suggested there might be a fuse on the AC unit itself. I guess I need to look at that as well. Not entirely sure where to look, but apparently somewhere near the air return vent.

 

[danemayer]

I think the thermostat wires go to a box on the underside of the living room air conditioner. If you have a voltmeter, you might take a reading on the wires as they attach to the thermostat to see if you have 12V there. If not, the box in the air conditioner might be the next place to check.

Be careful when you open the electrical box in the ceiling. You'll probably have to stand on something and the last thing you want is to get bitten by 110V while standing on a chair or step ladder.

 

[CapnSteve59]

Finally found my mutlimeter and checked, but no juice to the thermostat, so I'm down to the box. The tabs on the grille seem quite fragile, but I'll look at it again tonight when I get home. Spent half a day yesterday with Directv trying to get their install done. Turned out okay, but somewhat frustrating trying to program the remote to my Toshiba TV.