The furnace and thermostat should be 12VDC. The 120VAC is for the fan and compressor in the roof A/C unit. There is a 12VDC relay for the 120VAC.
If your dry camping, the thermostat will control the furnace, not the A/C unit. This is assuming you DONT have in command.
I would assume the in command system operates the same way.
2012 Copper Canyon 273FWRET being towed by a 1994 Ford F350 CC,LB,Dually diesel.
Airlift 5000 bags, Prodigy brake control, 5 gauges on the pillar.Used to tow a '97 Jayco 323RKS.
Now an RVIA registered tech. Retired from Law enforcement in 2008 after 25+ yrs.