SOLVED: Furnace comes on when Dometic AC is on

TxCowboy

Well-known member
Got chilly in the RV last night so I turned on the propane heater using the Dometic thermostat. Furnace fired right up.

Then I noticed that the AC had turned on and was running as well. (Both the propane heater AND the AC are on simultaneously.)

I can't believe that this is normal but I did research the manufacturer's manuals and did not see this issue addressed. I eventually turned off the AC by tripping the AC circuit breaker.

Is this a problem with the thermostat sending an erroneous signal to the AC unit? How can it be corrected?

Your thoughts, please!
 

travelin2

Pennsylvania Chapter Leaders-retired
Re: Dometic thermostat -- Turned on the furnace and the AC comes on also!

Probably you need to set the thermostat to the auto fan setting. I did. Believe it's covered in the owners manual.
 

danemayer

Well-known member
Re: Dometic thermostat -- Turned on the furnace and the AC comes on also!

When the thermostat FAN setting is HIGH or LOW, the A/C fan runs continuously regardless of whether the thermostat is set to COOL or to HEAT. As travelin2 said, change the FAN setting to AUTO. To do so, cycle the mode to FAN and press the + or - key until it's on AUTO.

This and other helpful information is in our owner-written Heating and Cooling Guide.
 

TxCowboy

Well-known member
Re: Dometic thermostat -- Turned on the furnace and the AC comes on also!

Thanks, guys! Problem solved.
 

mdonnell

Member
Thanks for the solution! I had the same issue and reset the Fan on the thermostat and all is good! I am really glad because it is going down to 39 degrees tonight.
 
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