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  1. #1
    Join Date
    Apr 2009
    Post Likes

    Thermostat Auto On Doesn't work properly

    I have A Honywell RTH230B thermostat hooked up to a Lennox G50UH furnace. I also have a Carrier A/C. The problem I having is that if the heat and the A/C switched is turned off and I turn the fan switch to "On", it turns on the fan and the A/C. THe heater and the A/C both worked properly with I have the fan switch on AUTO. Below is the wiring from thermostat to furnace:

    Thermostat ------------ Furnace
    Rh R
    Rc (jumper
    to Rh
    W W
    Y Y
    G G

    There's also a cable with two wires coming in from the A/C unit. The red wire is hooked up to the C terminal and the white wire is hooked up to the yellow terminal.

    It seems like everything is hooked up just fine. Should I try a new thermostat or does anyone see a potential problem with the wiring.


  2. #2
    Join Date
    Mar 2009
    Several Miles from Sane
    Post Likes
    First welcome, second please re-read site rules (DIY),

    That said, it sounds like the condenser and the fan are connected together somehow. What needs to happen is that the "G" terminal need to start the fan. Someone likely didn't install an isolation relay to separate the cooling signal and the fan signal.

    try < We don't give recomendations for DY sites> if you need specific advice on how to do so.
    Last edited by beenthere; 04-23-2009 at 06:25 PM. Reason: Removed DIY site name
    If sense were so common everyone would have it !

    Any advice provided is worth exactly what you paid for it, not a penny more not, a penny less !!

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