I have a dometic dual-therm rooftop RV air with analog thermostat. When I set the thermostat to heat, the unit will hum but the fan does not turn and no air is coming thru vents in the floor. Then unit will blow cold air (hums and fan turns) when thermostat is on cool, but it won't turn off unless I shut it off at the breaker. What could be wrong?

SOURCE: Dometic Rooftop Dua-therm unit 1997.Fan runs,but

you need alot more info to help you. Which fan runs. The compressor could be out on high pressure if the cond fan failed. You really need to do a lot of trouble shooting to isolate the problem.

Mike Butler

• 6674 Answers
• Posted on Jun 05, 2010

SOURCE: Rooftop RV Air Conditioner: replaced capacitor on dometic 59516-531 steal trip...

You need to borrow a clamp on style amp gauge, and check amp draw on black wire in box where hydro wires connect. (PLEASE, be careful, and if not experienced in this type of test, don't try it, due to likelihood of getting a shock. ) If it's the compressor kicking in that's causing the breaker to trip, and capacitor is good, then it's usually a problem with either low incoming (supply) 110-120 AC voltage, which will cause high amperage draw, or compressor on it's way out causing high amp draw. If it's only drawing 15-18 amps, and your tripping a 20 amp breaker, then breaker is getting weak.

SOURCE: Dometic 15,000 rooftop AC was

Bad fan motor or start/run capacitor! The unit overheats and shuts down to protect when high limit is reached