replace Furnace Control Board Or not

Discussion in 'HVAC Heating & Cooling' started by kp9999, Feb 20, 2012.

  1. kp9999

    kp9999 New Member

    Feb 20, 2012

    My master bedroom thermostat when set to 75F(for example) run only upto 68F.we called a technician and he diagnosed it.
    He claims that( i also saw what he was doing) when thermostat was set to increase the heat, due to control board malfunction AC also starts to work. As a result at the same time Heat and Cool Air starts to flow.Technician wants 4777$ to change the board(timer control board on furnace) with 1 yr labor + 1 year parts warranty.

    I was able to see the furnace starts to ignite gas flames and also AC starts to run and i can feel freon tube get chilled and the vent let out some cold air as well.
    Technician already charged 80$ for diagnosis. I am trying to call someone else for 2nd opinion. Also want to know if i can just buy the contrtol board and fix myself.

    Any advice please?

    Last edited: Feb 20, 2012
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    While it could be in the furnace control board, it could also easily be a wiring error or a bad thermostat. Hopefully, the tech was decent. As to whether you can replace it yourself, no idea what your skill level is. IF that's it, and it is correctly replaced, that should fix it. Most of these things are designed to be plugged in, but it's possible it may require soldering, or removing wires from terminals and reattaching them to the new board. What you'll pay retail for the board may be as much or more than you'd pay a tech for it since he'll get it at wholesale. In the interim, you could just shut the CB off for the a/c compressor, then, even if the board is calling for cooling, it won't run and you'll be warm. No need to fix this now, but you'd want to get it done before a/c season comes up.
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  4. cacher_chick

    cacher_chick Test, Don't Guess!

    Jan 5, 2008
    Test, Don't Guess!
    Land of Cheese
    You didn't mention what kind of furnace that you have.

    The control board for my furnace is less than $200.
    The entire furnace didn't cost what you are talking about.
  5. jimbo

    jimbo Plumber

    Aug 31, 2004
    San Diego, CA
    Depending on what make/model, his cost for a control board is probably $75 to $150. He will have to mark that up. And if your unit is pretty old, the board may be the manufacturers "universal replacement " board, meaning you may have to "negotiate" where all the wires go.

    If this were an air handler, I could see board problems. The furnace "board" is really just for ignition. I would tend to suspect the thermostat, although they do not normally fail in this manner.

    If you have your model number, or the part number on the board, you can usually find the boards on line.
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