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  1. #1
    Join Date
    Aug 2003
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    Goodman 2.5 ton hp w/10k heat blowing low voltage 5 amp fuse

    I don't do much service work. I keep blowing low voltage fuse on control board in air handler. I replaced t stat still blew fuse. I removed t stat but left t stat base on wall with all wires still connected to t stat base and still blew fuse. I removed all low voltage wires from t stat, air handler, and outdoor unit made sure they were not touching. I Checked all low voltage wires against each other to make sure they were not grounded out against each other with continuity meter, all woes checked out good.

    Outdoor unit I went from ground to each low voltage wire with all wires not touching each other and I got:

    O= 500 ohms
    R= .7 ohms
    W= 5.2 mega ohms
    Y=1462 ohms
    Blue= 500 ohms

    Air handler all low voltage disconnected:

    W= 10 ohms
    R= .8 ohms
    B= .2 ohms
    G=1500 ohms
    Brown =16 mega ohms.

    On air handler unit going from ground to each air handler unit wire I had continuity from ground to red and ground to blue.

    Any recommendations what I can check next without throwing parts at it?

    I mostly do shop duct work, I have installed probably 30 residential units in my 32 years but I don't do much service work.

    Thanks

  2. #2
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    So what happens with all low voltage wires disconnect from the air handler ?

  3. Likes DavidDeBord liked this post
  4. #3
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    Thread Starter
    I need to double check but I believe with all wires disconnected to air handler and all low voltage wires disconnected the fuse didn't blow when I powered on the air handler. but I need to double check I will try it again. I installed this unit 3 years ago it's never had an issue till now.

  5. #4
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    You can add one wire back on at a time to find the problem child.

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  7. #5
    Join Date
    Nov 2006
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    Athens, Ohio
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    Installl a fuse in each wire and see which one blows.
    AOP Rules: Rules For Equipment Owners.

    Free online load calculator: http://www.loadcalc.net/


    There = not here. Their = possessive pronoun. They're = they are
    It's = contraction of it is. Its = the possessive form of it
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    Questions should end with a question mark "?" Statements end with a period "."

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  9. #6
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    Those Lil Popper fuse breakers sure come in handy on times like these.

  10. #7
    Join Date
    Nov 2014
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    Philadelphia area
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    You said you have continuity from ground to red and ground to blue? Check for continuity from the 24volt side of the transformer to ground. Sounds like the transformer might be your problem

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  12. #8
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    Thread Starter
    Update, I hooked one back at a time. I did all t stat to air handler wires first. All good was able to run ah fan, and emergency heat fine with no issues, this tells me it must be on the outdoor unit. Next with all outdoor wires disconnected I connected red wire from outdoor unit to ah/ t stat and powered on ah and the 5 amp fuse blew. The rest of the heat pump wires (o,b,w,y) were disconnected. What can I do now to troubleshoot, is it the defrost board. The T stat was set to off when I powered the air handler beaker on which blew the 5 amp fuse.

    Thanks for all the help.

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  14. #9
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    Disconnect the red from the outdoor unit and see what happens.
    Did you follow the wire between the two units ? Look for a rub thru at any penetrations. Outside wall for one.

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  16. #10
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    Jun 2008
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    Defrost Board is hook up to all other wires except green(control board only) ;
    if that fan motor stay on after you unhook all wires from outside except green and red then its the defrost board !
    look @ IT CLOSELY (the defrost board) if its got brown burns @ diodes.
    Matt 7:12 The Golden Rule
    "Do for others what you would like them to do for you. This summary of all is taught in the law and the prophets.

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  18. #11
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    Mar 2015
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    Hamersville, Ohio
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    Quote Originally Posted by kdean1 View Post
    Installl a fuse in each wire and see which one blows.

  19. #12
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    Aug 2003
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    Thread Starter
    I always run extra low voltage wires to heat pump. I tried another low voltage wire going outside to red heat pump wire and 5 amp fuse still blew so I don't the low voltage wire is shorted anywhere.

    When u say add more fuses do you mean add a fuse on every low voltage wire coming off heat pump control board?

  20. #13
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    Lookin like it's the board then. Disconnect all wires from the board except red. If it blows look your board over good as mentioned.

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