Puzzler on our Furnace I have a suburban furnace in my 2015 Columbus. The thermostat runs up to the air conditioning unit then back down to the heater. The controller box in the air conditioning in went bad and the furnace quit working but the air conditioning still works. I found the two wires that controller the furnace at the furnace, brought them out and installed a thermostat separate for the furnace. Works great. We only use the heater first thing in the morning for a few minutes. It uses to much gas and battery to be worthwhile when Boondocking. We also have a mr. heater big buddy heater that we use most of the time and love it. Yes we leave a couple windows cracked an would not sleep with it on. It one of the best buys for our trailer that we use the most.