12V Power feed blowing fuses

Discussion in 'Wiring' started by mprachar, Jan 11, 2019 at 7:08 PM.

  1. mprachar

    mprachar New Member

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    Oct 2, 2018
    I blow a fuse on my PU every time I plug it into my TV with the 7pin.
    Please let me know if you have thoughts.

    The main power from the TV, the wire from the camper batteries, and the 12V cable to the power converter all attach together in a wire nut in the camper. The only wire with an inline fuse is the line to the batteries, which I added when I was replacing the battery lines.

    The power converter is a little one with a 15 amp capacity. I have tried 20 amp, 25 amp, and 30 amp fuses in the line to the batteries and every time I connect my tow vehicle to the camper it blows the fuse to the camper batteries. If I try to plug the camper in while the TV is running, I get a large spark when connecting.

    My thoughts:
    1: A possible problem with the 12 volt side of the fridge (it is the only thing running while we are on the road)
    2: Maybe there isn't supposed to be a fuse on the battery line.
    3: The wiring configuration is wrong from the outset.
    3: There is a short in the line somewhere that is only impacted by the TV.
    4: The TV outputs too high in amps and blows the fuse (I don't think that's how amperage works).

    Other considerations:
    1: There are no problems with shore power, and when I replace the fuse, I have battery power. The only problem is after plugging into the TV. Of course that disconnects the batteries and I only have shore power until I replace the fuse.
    2: I have good ground connections with self-tapping screws into the frame of the trailer.
    3: There has been no impact on the fuses in the TV or in the Power Converter despite being a 24 year old converter with very finicky fuses.

    Any thoughts would be appreciated.
    Thanks
    - Matthew
     
  2. joet

    joet Well-Known Member

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    Mar 16, 2011
    Elkins WV area
    Check the politary on the TV plug/cord. ( wiring configuration was wrong to start with) Sounds like something is reversed
     
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  3. mprachar

    mprachar New Member

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    Oct 2, 2018
    Thanks, but no go. I checked polarity on the TV and the camper side. White wires are grounded and black wires are hot. Black to black and white to white when connected. Everything looks good at that connection.
     
  4. SteveP

    SteveP Well-Known Member

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    May 21, 2015
    My first thought is that your batteries are seriously depleted, damaged, or incorrectly connected.
     
  5. WrkrBee

    WrkrBee Well-Known Member

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    May 23, 2018
    South Carolina
    Can you remove the fuse, plug into the TV, and reinstall the fuse? Agree with SteveP about the battery condition. Looks like TV alternator (could be 70 - 100+ amps depending on TV) is trying to put a high rate to PU battery.
     
  6. mprachar

    mprachar New Member

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    Oct 2, 2018
    Batteries are new and work fine when not connected to the tow vehicle.
     
  7. mprachar

    mprachar New Member

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    Oct 2, 2018
    The fuse sparks and blows right away.
     
  8. joet

    joet Well-Known Member

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    Mar 16, 2011
    Elkins WV area
    You got something hooked up wrong!!
     
  9. mprachar

    mprachar New Member

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    Oct 2, 2018
    Thanks to everybody for your help.
    joet and SteveP were exactly right.
    I worked everything back to some poor wire connections in the camper, replaced those and nothing was fixed.
    I was watching a video on testing batteries and it suddenly hit me: they are wired in series.

    The previous owner had two 12 V batteries on the camper, but they were both shot. I replaced with two more 12 V batteries and replaced the wiring, using the old wires as a guide. It was in a series with 24 volts going to the camper. The fuse was protecting my tow vehicle from the camper batteries!

    I changed the wiring to a simple parallel wiring and it fixed the problem.
    Thanks again for the help.
    - Matthew
     
  10. nineoaks2004

    nineoaks2004 Every meal is a picnic and every Day is a holiday

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    Oct 15, 2006
    Graceville, Florida
    It is a good thing that the fuse blew and 24V did got get inside as a lot of items would have been smoked. The po probably had 2 6V batteries wired in series, this would have explained the hook up wiring.
     

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