I have a Dometic Duo-Therm AC on rooftop of a 2006 Dutchman Travel Trailer which we just purchased from an individual. Blows hot air out of the A/Cand the furnace blower motor runs at the same time when the thermostat is set to cool.

SOURCE: will not shut off

Sounds like a stuck relay on the unit itself. Maybe there is a short in the control wire that comes from the thermostat that activates the fan.

The thermostat probably has one hot wire at all times. The thermostat then chooses which wire to send the voltage down based on your selection. One of those wires is probably for the fan only. Make sure that it is in good condition (no bare, pinched or wires)

SOURCE: Dometic duo therm does not cool or heat...

it should never have to be recharged unless there is a leak. so you should isolate the leak with dye injectable into the system w/ the freon and correct it, then fully recharge system.

woobie dog

• 1273 Answers
• Posted on Aug 01, 2009

SOURCE: Dometic air conditioner blowing cool air

When the cooling slows down, but water is still running off, usually something is icing up. You can turn the unit off, and let it thaw, and try again. Sometimes, if the humidity is high, this is more pronounced. It sounds like you are low on refrigerant. That implies that you have a slight leak. You should have the unit serviced, and the leak repaired.
Best regards, --W/D--

SOURCE: Duo-therm rooftop RV a/c - one unit cools fine,

Hi, you would need to get up top to find out what is going on. Remove the cover, check to see if the small condenser fan motor is on and running, if not, touch it carefully after it has been on a while to see if it is hot. If so, try giving the blade a spin. If nothing, this will be your problem. Check to see that the compressor is also on and running. Feel the copper lines coming from it, one should be very cool to the point as to condensate. Be very careful with the smaller discharge or liquid line as it could be around 110 degrees F. Look at the run capacitor to see if it is leaking oil, swollen up or even busted or split open. If so, this will cause your compressor not to run. Look it over and keep me posted. It may have a small leak and has lost its charge also. Get back to me and let me know what you have found. Make sure you have the correct voltage to it also.
Sincerely,
Shastalaker7