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  1. #1
    Ed
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    Default What happens if you cross cables while jumpstarting a car?

    I should know the answer to this one but I don't! My gf left her lights on on her 93 Civic Coupe and it had to get jump started. The guy who jump started her car crossed the cables, and she said there were all these sparks but it did start and she successfully drove home.

    Next morning, the car is dead as a doornail. She bought a new battery, but it's still dead as a doornail. Jumping the battery doesn't do anything - the car's completely dead.

    Any ideas on what happened? Why did the car run for awhile but is now totally a goner? What could get damaged by crossing the cables?

    Any help's appreciated; the car's parked on the side of the street that gets sweeped by the city tomorrow and if we can't move it, a $30 parking ticket's on its way.....

  2. #2
    Senior TEAM Member Rally Man's Avatar
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    Default Re: What happens if you cross cables while jumpstarting a car?

    From what I’ve been told, by mechanics and my old mechanics teacher, it fry’s the cars computer. As to why it ran, and now doesn't.....

  3. #3
    [FJ] Specialist icemanZX3's Avatar
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    Default Re: What happens if you cross cables while jumpstarting a car?

    total protonic reversal... imagine every molecule in your body exploding at the speed of light..

    that would be bad

  4. #4
    Devil's Advocate. Just to cheese you off. ax0n's Avatar
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    Default Re: What happens if you cross cables while jumpstarting a car?

    I should know the answer to this one but I don't! My gf left her lights on on her 93 Civic Coupe and it had to get jump started. The guy who jump started her car crossed the cables, and she said there were all these sparks but it did start and she successfully drove home.

    Next morning, the car is dead as a doornail. She bought a new battery, but it's still dead as a doornail. Jumping the battery doesn't do anything - the car's completely dead.

    Any ideas on what happened? Why did the car run for awhile but is now totally a goner? What could get damaged by crossing the cables?

    Any help's appreciated; the car's parked on the side of the street that gets sweeped by the city tomorrow and if we can't move it, a $30 parking ticket's on its way.....
    The battery might be completely fried, and maybe the alternator, too. If both are fried you'll have a hard time starting it. Does it even crank over when you have jumpers hooked up?

  5. #5
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    Default Re: What happens if you cross cables while jumpstarting a car?

    I have heard, very recently as a matter of fact, on another car forum I go to that this happened to one of the poster's GF's and she needed a new ECU and main wiring harness. It fried the whole deal.

    If that winds up being the case here, you shouldn't feel too bad. In some cases the battery explodes and seriously [censored] up anyone within blast range. Acid everywhere etc...

  6. #6
    Illage Vidiot Mr. Zetec's Avatar
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    Default Re: What happens if you cross cables while jumpstarting a car?

    I actually witnessed this on a POS trans am and an other pos tuarus, only thing that happened is the jumper cables welded themselves to the batter on the trans am the one we reversed, they both started right up, well after a few cranks, both cars where 90 and 91 i think

  7. #7
    [FJ] Specialist
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    Default Re: What happens if you cross cables while jumpstarting a car?

    battery alternator and ECU.

    btw, sometimes the dumbest people in the world are hte ones in AP classes.

  8. #8
    Ed
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    Default Re: What happens if you cross cables while jumpstarting a car?

    The battery might be completely fried, and maybe the alternator, too. If both are fried you'll have a hard time starting it. Does it even crank over when you have jumpers hooked up?
    Nope, it won't even crank over. Not even the clicking of the starter solenoid - and this is a brand new battery that she put in after it wouldn't start yesterday morning. Totally dead.

    What's puzzling though is that it ran fine after the cross jump - she drove it home without incident. It was the next morning when she was leaving for work that she found it totally dead. Could the computer have fried itself after the fact? I don't see how it could....

  9. #9
    Don't Call Me Gaga!
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    Default Re: What happens if you cross cables while jumpstarting a car?

    The link from the battery may be toast, but the alternator connection may be fine.

    A car will run on the alternator alone just fine, which is why it probably drove home afterward... once the alternator stops spinning though, you're back on the battery connection... which apparently has been damaged.

    Somebody is going to have to get serious with a multimeter to track this one down.

  10. #10
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    Default Re: What happens if you cross cables while jumpstarting a car?

    if you get no sound...you probably killed the wiring...

    This happened to me in my neon a while back when the other guy put black to positive and I had to pull the cables off with a shirt it was so hot. It fried my wiring harness and I found it all after about 4 hours of tracing wires with a multimeter. I'd feel wiring bunches and see if there's any places that bend more easily...if you can, cut them open and take a look at them

  11. #11
    Not Special Enough TXFO's Avatar
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    Default Re: What happens if you cross cables while jumpstarting a car?

    I did that in my old truck. it blew out the radio antenna adapter and made some smoke but it was fine. (87 Nissan)

    when she turns the key, what does the gauge cluster/odometer do?

  12. #12
    Ed
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    Default Re: What happens if you cross cables while jumpstarting a car?

    I did that in my old truck. it blew out the radio antenna adapter and made some smoke but it was fine. (87 Nissan)

    when she turns the key, what does the gauge cluster/odometer do?
    Absolutely nothing - and keep in mind too that she put in a brand new battery after this whole thing happened since we assumed it needed a new one.

  13. #13
    Not Special Enough TXFO's Avatar
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    Default Re: What happens if you cross cables while jumpstarting a car?

    yeah but what does the odometer readout say when you turn to start? do the gauge lights come on? do the needles sweep? is everything dark and inactive?

  14. #14
    Not Special Enough TXFO's Avatar
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    Default Re: What happens if you cross cables while jumpstarting a car?

    you might try getting a multimeter and measureing from batt- to the chasis. if its wide open than she blew the ground wires out. measure the resistance from batt- to the starter housing also.

  15. #15
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    Default Re: What happens if you cross cables while jumpstarting a car?

    i'm gonna have to say the battery cables are fried. since the car was running fine on the way home i highly doubt the computer is dead.


 
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