Welcome to the forum
The furnace is operated by a thermostat, and there are a few different brands and styles. Could you maybe elaborate a bit more? What model of trailer?
If there is a thermostat on the wall, can you describe it?
Your profile shows a 2011 Montana, and your post refers to a 2006 ???
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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.