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  1. #1
    Join Date
    Jan 2020
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    5 amp fuse constantly blows

    Hi guys! My name is Sunny and I’m new to this site and I just want to say first off that I truly appreciate any response and feedback that I receive! I’m a Maintenance Technician at a apartment community where I live and right now I have an issue where a resident’s 5 amp fuse on the board in their air handler continues to blow every few hours. It doesn’t blow immediately and their heat will work for a few hours but it will eventually blow again. Any advice on diagnosing this issue will be greatly appreciated! Thanks a lot!

  2. #2
    Join Date
    Jan 2004
    Location
    PA
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    Is this a heat pump system. If so, have you checked the outdoor unit.
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  3. #3
    Join Date
    Mar 2010
    Location
    Pleasant Hill, MO
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    If that's a heat pump, it sounds like a short in either the defrost or maybe second stage heat. Might try manually tripping a defrost cycle and see what it gives you. Hopefully it would at least allow you to replicate the issue to trace it

  4. #4
    Join Date
    Sep 2007
    Location
    edmonds wa
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    You need a good amp meter around the fused line and then start cycling all the components, if nothing shows a high amp draw, start looking at all the control wiring for chafing or bare spots.
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  5. #5
    Join Date
    Aug 2009
    Location
    Beatrice, NE
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    You have a intermittent short. As has been said it may be from water getting on a wire during defrost. It could be from a vibration against metal, etc. Get out your shovel cause the only way to find this is to "dig" into it. If it were constant it would be fairly easy to track down. Being intermittent you will almost have to live with it till it happens. As said you may be able to run the system in all it's modes but trying to shorten the time frame may not let all the components of the short come together. You may be able to get creative with smaller fuses to isolate the problem but can't go into particulars on an open forum.

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  7. #6
    Join Date
    Mar 2008
    Location
    Fuquay Varina, N.C.
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    Instead of constantly blowing fuses, get a product called short pro, you can find it on amazon, if you want to see it in use, look up Dirty maintenance show on you tube, done by Lex, who is a maintenance man himself, he recently did a video on a short in an indoor unit. He might be able to give you more advice than we can share on this open site!!!


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  9. #7
    Join Date
    Apr 2015
    Location
    Martinsburg, WV.
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    Check the reversing valve. Also, older carrier/bryant units were notorious for the low pressure wire rubbing on the cabinet doors.

  10. Likes Dhumphries82, Core_d liked this post.
  11. #8
    Join Date
    Apr 2019
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    Sounds like a bare wire for reversing valve rubbing and causing the short when goes into defrost. Switch to Ac and see if blows immediately if not then keep digging.


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  13. #9
    Join Date
    May 2018
    Location
    FLORIDA
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    302
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    its probably a short
    check the thermostat if is old sometime can create a short
    or could be thermostat wire with broken insulation touching metal or another wire
    sometimes contactor coil is shorted too
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  14. #10
    Join Date
    Oct 2002
    Location
    Plano, TX
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    2,417
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    May try to fuse each control load with a one amp fuse. RV,contactor, fan cotactor. See which one blows and that will narrow it down.

  15. #11
    Join Date
    Mar 2019
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    check behind defrost board for lizard or frog. also RV will blow if valve is sticking.

  16. #12
    Join Date
    Aug 2009
    Location
    Beatrice, NE
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    Check LPC & HPC. I ran into a couple of the screw on with the plastic cover on the switch. The plastic was cracked so water could get in which could cause an intermittent short.

  17. #13
    Join Date
    Jun 2019
    Posts
    49
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    I would put a little 5 amp "lil popper" breaker on- (that is brand)- to avoid wasting fuses. (in addition to what everyone else has said). When I have had this problem- I found wiring issues from previous tech---check each wire with schematics- it just takes a few minutes, but then you know where you stand. You know everything is wired properly- and then you can start inspecting wires and circuits for shorts like the others have said. In the meantime you are not wasting fuses.

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