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  1. #1
    Join Date
    Oct 2006
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    I need some advice. I have to Carrier/Bryant units in my attic. Both of them have the same circuit board (HK42FZ009). I went to turn on the heat upstairs and downstairs last night, and the thermostats went dead. I checked them this morning, and I was getting a "24" error message, which is the their is an open short on the 24v connection. I have bipassed the Com, by using a thermostat with batteries, instead of a 24v connection. It does the same thing, it blows the 3ATC fuse each time. By bypassing the com, I feel that I have eliminated a short in the wiring. BOTH of my units started doing this only when the heat was turned on. We also had a surge back in September. The AC still worked, but hadn't checked the heat till now. Does this sound like a furnace problem, or circuit board problem? Any help would be appreciated.


  2. #2
    Join Date
    Oct 2006
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    circuit board problems

    try circuit board i had a tempstar unit would work fine in cooling mode soon as i turned on the heat it would blow the fuse after i went thru about 2 or 3 fuses i went and got a c board works fine now. unless you have the right tools to ck it with its better to replace it . its hard to troubleshoot a board just get one and try that

  3. #3
    Join Date
    May 2006
    Philadelphia, PA
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    Or you could call a contractor and have them troubleshoot the systems and let you know what is wrong.
    Climate Control Solutions for your Home or Office

    Serving Northeast Philadelphia and Surrounding Areas

  4. #4
    Join Date
    Jan 2001
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    Just What the heck is an open short......~:>

    Call the original installer back...if you were satisfied with their work........

    Is this the first winter the furnace has seen use...if it is there could be a problem with the thermostat wires....either a wire is cut in two pieces (open) or two wires are touching (short).....

    But you cant tell for sure over the internet.....

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