Welcome to the forum
Congrats on your new trailer. It's NORMAL for new owners that didn't get proper instructions, to ask this question. I figure you have the square digital read out Dometic thermostat. One button on left and two on right. Here you go:
The LEFT button allows you to scroll through the different operations- FAN, COOL, HEAT and OFF. In FAN mode the right buttons allow you to adjust the speed from Hi to Lo the AUTO.
If the FAN is set to Hi or LO, and you go to COOL, the fan runs all the time and the compressor cycles based on set temp. If the FAN is set to Hi or Lo and you go to HEAT, the AC fan will run AND the furnace fan will run.
If the FAN is set to AUTO and you go to COOL, both the fan and compressor will cycle based on set temp. If the FAN is set to AUTO, and you go to HEAT, just the furnace fan will run.
If you NOT PLUGGED INTO shore power then anything in in AC won't work and it doesn't matter what the fan is set to. Your furnace operates on 12VDC so,as long as you have a decent charge, you will always have heat
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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.