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Thread: What would happen if you crossed the battery cables while installing battery?

  1. #1

    Default What would happen if you crossed the battery cables while installing battery?

    Hypothetically, what would happen if one were to cross the battery cables when installing a new battery on their jeep (install the postive on the negative and vice versa)? If they saw one or two sparks at the posts when attaching it, and then tried to crank the engine and nothing happened - and then they realized what they did, after the fact.

    Ok, I confess, I did this to my motorcycle today, not my Jeep, but since this could happen to a fellow jeeper and since this board has offered up such a wealth of knowledge in helping me fix and diagnose my jeep, maybe yall could help a man out with this general electrical question.

    The battery was tested after, full charge still. The bike - DEAD - no lights or anything. The master 30A fuse was still fine, which is strange.

    Sorry if this is OT, but it could happen to a jeeper too so maybe it will serve as a lesson to those who stupidly decide to engage in conversations while installing a battery with paying too much attention...

  2. #2
    ***** ******
    Join Date
    Dec 1969
    West Palm Beach, San Diego, Hawaii


    I'd probably start by checking the rest of the fuses (begining with the ignition circuit).

  3. #3


    yeah, they're all good...thanks though.

    maybe the polarity in the battery reversed, so although it is holding a 12V charge it is all messed up now?

  4. #4
    I love Jeeps vtx531's Avatar
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    Mar 2003
    Kalamazoo & New Hudson, MICHIGAN


    I accidentally hooked up my winch cables backwards and it started smoking from the solenoid box. Still works good though.
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  5. #5
    Join Date
    Mar 2002
    Greenwood Lake, NY


    Ouch that sucks. See if there is a fusible link in there somewhere.
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  6. #6
    Registered Knuckelhead's Avatar
    Join Date
    Nov 2005


    Quote Originally Posted by snosurfa7
    maybe the polarity in the battery reversed
    Only if you happened to fully discharge it and then recharge it reversed. IMO
    "Here's my strategy on the Cold War:
    We win, they lose."
    - Ronald Reagan-

  7. #7
    Join Date
    Nov 2000
    Boston, MA


    This did happen to my Jeep.. sort of. While attempting to jumpstart my jeep the cables were put on backwards. Fuse #17, the ignition off draw circuit that includes the interior courtesy lights, parts of the instrument panel, radio presets/clock, and the OBD port. Fuse 17 burnt out. Also there is a 100 amp fusible link in a heavy gauge wire ~6 gauge wire that goes from the underhood fuse box to the alternator. That fusible link burnt out as well. Luckily the key to the dead jeep was out so nobody turned the key to the on position to potentially fry all the circuits. The only circuit that was closed/connected at the time was the fuse 17 circuit. I replaced the 100 amp fused wire and fuse 17 but now there's a slow drain on the battery. After a few days of sitting the battery doens't have enough juice to start the jeep. I had a post about this around a week ago. I did get a lot of suggestions but none of them really worked. SO that's what happens if you reverse the polarity on your jeep, with the key in the OFF position. I'd hate to see what would happen if you tried to start the jeep. Best of luck.

  8. #8
    Join Date
    Sep 2000
    who cares, I'm west of Central.


    there's a good chance you shorted out the battery and it's junk now. you would need a mid-tronics tester to check for sure
    I figured it was time to change this.

  9. #9


    I had a friend do this once when attempting to jump start a vehicle. It fried his alternator. Check your electrical components and all fuses and relays. Basically, the current will travel through the circuit until it finds a weak link at which point it will escape.

    Good luck, it's reasons just like these that I hate electrical, plus, it hurts when you lick it.
    '92 YJ with stuff

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