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DazedNConfused's avatar
DazedNConfused
Explorer
Nov 05, 2013

Bad thermostat?

Was camping over the weekend and temps got down into the upper 30s. Fired up the furnace in the morning to take the chill out and both the furance AND the A/C came on at the same time. Huh. Odd. I set the thermostat to all off which shut down the A/C...followed by the furance a minute or so later. Waited abut 5 minutes, chose heat again from the thermostat, and the same thing happened -- both heat and A/C. So I shut off the A/C at the breaker panel and let the furnace run figuring I'll deal with it when I got home. Haven't tried it since being home...but wondering if others have seen this.

Thanks,
- DNC

16 Replies

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  • golf_bears's avatar
    golf_bears
    Explorer
    Nov 07, 2013
    It actually makes sense. Heat rises and having the AC fan on helps move the hot air off the ceiling down towards the floor as well as moves hot air around the inside of the RV.
  • RAINEYTXX's avatar
    RAINEYTXX
    Explorer
    Nov 07, 2013
    If you have a small square Dometic digital thermostat, if you do not set the fan to "auto" and select fan speed high or low, the roof a/c fan will run with the heater. Maybe Dometic's thinking it helps move around the air in the trailer but the heater should provide adequate flow to warm your trailer by itself.

    Make sure fan speed set to Auto
  • avvidclif1's avatar
    avvidclif1
    Explorer
    Nov 05, 2013
    The first time I used the heater in my new trailer it had very low air volume. Thinking it might have the blower on low I changed the thermostat from Auto to High and the fan in the AC came on, the heater never changed. Put it back on Auto and the AC fan shut off. Turns out the heater had a duct problem. I still don't know why the AC fan would come on when the heater is on. Just one of those things that keeps me scratching my head in wonder at the design engineers for the different RV systems.
  • DazedNConfused's avatar
    DazedNConfused
    Explorer
    Nov 05, 2013
    Page 9 explains what's happening. Thanks, Allworth. You're brilliant. I learned something new today. :)

    http://www.dometic.com/1fa178a7-95b8-4494-bb17-6af80e4c7895.fodoc

    - DNC
  • DazedNConfused's avatar
    DazedNConfused
    Explorer
    Nov 05, 2013
    Allworth wrote:
    My thermostat has a setting in the "Mode" menu that turns on both fans with either hear or air.

    I don't use it, but it is there if you cycle through all of the mode selections.


    Huh....interesting. It was actually a friend of mine that turned the heat on....so it's possible he got into this mode that you're talking about. I'll look up the manual for the thermostat and see if that's what's going on. Thanks for the tip.

    -DNC
  • Allworth's avatar
    Allworth
    Explorer II
    Nov 05, 2013
    My thermostat has a setting in the "Mode" menu that turns on both fans with either hear or air.

    I don't use it, but it is there if you cycle through all of the mode selections.

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