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  1. #1
    Join Date
    Dec 2011
    Location
    Mid-Atlantic
    Posts
    7

    Hmm Fuse keeps blowing

    My dad has a heat pump, when the heat is turned on the 3 amp fuse on the 24V red wire off the transformer is blown, a/c is fine. The transformer was replaced, the blower contactor reads 10 ohms across the coil, the backup heat contactor reads 15 ohms. Both work when contactor is pushed in.

    Someone told me that one would check all the low voltage wires to see if they are shorted. Does that mean one would disconnect the wire at both ends (at the thermostat being one end) and then check it to ground, hoping to read OL? Since it's the heat not working, either the white or red wire would be shorted, correct?

    Could it also be a motor problem?

    I'm only a few months deep in this trade and I'm curious.

  2. #2
    Join Date
    Dec 2002
    Location
    SouthEast NC ICW & Piedmont Foothills
    Posts
    7,635
    it's being caused by a short circuit; now it is in your best interest to ask a co-worker or an instructor to give you guidance on the proper procedure to determine where that short is.
    It`s better to be silent and thought the fool; than speak and remove all doubt.

  3. #3
    Join Date
    Dec 2010
    Location
    Down by the river
    Posts
    1,664
    I will give this fine piece of advice. Fuses do not go bad.

    You have a direction follow the road stillyout find the trouble

  4. #4
    Join Date
    Dec 2007
    Posts
    605
    Quote Originally Posted by dandyme View Post
    it's being caused by a short circuit; now it is in your best interest to ask a co-worker or an instructor to give you guidance on the proper procedure to determine where that short is.
    good advice!
    do it right the first time!

  5. #5
    Join Date
    Nov 2007
    Location
    Mississippi
    Posts
    1,367
    Is reversing valve energized in heat mode? What brand condenser does your dad have?

  6. #6
    Join Date
    Nov 2011
    Location
    USA
    Posts
    389
    You need to determine when the fuse blows: on a call for heat or second stage heat, during defrost, or just when the stat is set to "heat". If it's a Rheem product, could be the reversing valve circuit, since they energize in heat. You appear to have eliminated the aux heat control. Likely not the red wire or the fuse would blow in either mode. Check continuity on the "white" wire to common for low resistance. Based on the info you've provided it's the best bet for now.

  7. #7
    Join Date
    Jun 2012
    Location
    nampa idaho
    Posts
    66
    Might want to check the stat wire for continuity se if there is a short in the stat wire

  8. #8
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    18,792
    As a new tech, you should apply for pro membership so we can help you in the pro forums. Most technical information is not discussed out here in the open.

  9. #9
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,311
    Filing out your profile also helps us know who we are talking to.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  10. #10
    Join Date
    Dec 2011
    Location
    Mid-Atlantic
    Posts
    7
    Update: Someone came to help figure it out and he said it's probably thermostat trouble. We had a new thermostat put in by our local power company for free, which enables them to turn off our power for a short time if needed.

    Do you think it could actually be a faulty thermostat? All the wires seem to be hooked up correctly.

    Also for pro membership I think I need 15 posts correct?

  11. #11
    Join Date
    Mar 2008
    Location
    NC
    Posts
    1,461
    Yes. When you'll find guys a lot more giving with advice in the non-public forums.

  12. #12
    Join Date
    Oct 2011
    Location
    Chicagoland Area
    Posts
    4,681
    Screw the blown fuse. THIS
    Quote Originally Posted by JacJak View Post
    We had a new thermostat put in by our local power company for free, which enables them to turn off our power for a short time if needed.
    would be my concern. I'm curious to the reasoning and if this is something I have to look forward to in Al Gores America.
    Officially, Down for the count

    YOU HAVE TO GET OFF YOUR ASS TO GET ON YOUR FEET

    I know enough to know, I don't know enough
    Liberalism-Ideas so good they mandate them

  13. #13
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    18,792
    Quote Originally Posted by JacJak View Post
    Update: Someone came to help figure it out and he said it's probably thermostat trouble. We had a new thermostat put in by our local power company for free, which enables them to turn off our power for a short time if needed.

    Do you think it could actually be a faulty thermostat? All the wires seem to be hooked up correctly.

    Also for pro membership I think I need 15 posts correct?
    I would say that the recent hookup is more than a coincidence to your problem.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist

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