Question about Dometic Rooftop RV Air Conditioner

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No fan or heat on gas furnace

Appears to be in controller 3106481 electric kit relays sometimes click as if on and off.

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  • doug_k7evi
    doug_k7evi Dec 04, 2012

    i have trried exchanging funace boards, with no change. I have checked the voltages at the furnace and get strange results, it almost seems like both the control board in the AC unit and the furnace board are each locking the other out. These furnaces are not wired the same as the one in my Class C MH. I can not find schematics to assist my troubleshooting. I am a 35 year HVAC journeyman, but withoutprints I am at a standstill..

  • Mike Butler
    Mike Butler Feb 02, 2013

    4 wires from furnace normally, I -12v-, 1-12+, and 2 blue that go up to and back from thermostat. Simply joining those 2 blue together right at furnace connection after removing wires that run to thermostat from the blue wires, will confirm if furnace has the problem, or thermostat, provided wiring is good from furnace to thermostat.

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  • Dometic Master
  • 6,674 Answers

Once you have confirmed 12vdc to connector at furnace, just remove wires to 2 blue from furnace and join the 2 blue together to see if furnace runs. That just by-passes thermostat. What is furnace in? 12 volt-dc, or maybe 120AC, with 24V transformer if park model or similar.

Posted on Jan 27, 2013

  • doug_k7evi
    doug_k7evi Jan 29, 2013

    I am on the road in the other motor home. I will check this out again when I get back. As wired, there are at lest 3 circuts wire with blue wires. I will have to figure which blue wires are the ones you are refering to. Are those two in the ceiling units (at the control box)?

  • Mike Butler
    Mike Butler Jan 31, 2013

    Normally you can check right at thermostat, or go directly to furnace. At the thermostat, usually you will find 2 wires in a separate wire harness, like telephone line , which come from furnace, then another bunch of wires from control box at ceiling. If you have the separate wires at thermostat, ( usually red & white, or black & white ) and simply remove from wires at thermostat and join the 2 together, which completes the circuit for furnace only. But, if at all in doubt or wires all clumped together and you get confused, go to furnace and look where wires connect to furnace. There you will usually see 2 blue wires. Take the 2 blue coming out of furnace and join those 2 together and give furnace a few seconds to start up. The 2 wires connected to those blue wires, should be the same as the 2 at thermostat. By joining the 2 blue after you remove the 2 that are connected to them, you are by-passing thermostat. If it runs, then stops when you pull those 2 blue apart, then all is well there.

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