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  1. #1
    Join Date
    Jul 2008
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    hh84aa021 printed curcuit board

    The board I had replaced was a hh84aao15 from a D & N furnace. The problem is, the blower run constantly and no matter what resistor or jumper I have cut, it doesn't change. Carrier Techs can't explain their own replacement product.
    Can anyone help?

  2. #2
    Join Date
    Jan 2001
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    Sounds like the old board was fine and you have just lost 24 volts.

    Thats usually what causes a DandN or any other BDP furnace to have a continually operating blower....

    Of course you could have other problems....but loss of 24v is what I would look for first.

  3. #3
    Join Date
    Jul 2008
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    Hmm old board as well as blower motor/no good

    This board is new, with new transformer and new power cord. I thought it was a bad NEW board and bought another one---Nope--samething.

    Board/transformer & power cord is out on the counter top--plug it in and 5 sec. later blower relay makes sending (115v)power to low speed tap.

    Carrier has instructions to disable this occurrance, but their instructions do not work.
    Slakey Bros. in California called Carrier and 2 field service techs did not address the stand alone problem, they were saying things like what you said.

    It's in the board design, there are so many jumpers that could be cut, but no instructions on which one to cut!
    Technical writer wrote only two situations for this board. I was hoping someone in the field that has ran into replacing these boards knows what jumper to cut....and its not RS18 like the instructions say, niether JWS1, because that sends 24 volts to R-W.

    I'll have to admit, this one seems no one has the correct answer. Especially the ones that built it and work for carrier.

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