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Installed wrong battery reversed posts. Won’t start

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Old Feb 25, 2018 | 05:58 PM
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Installed wrong battery reversed posts. Won’t start

08’ g35 sedan

Hey all, first off I feel like an idiot, purchased battery from autozone and the guy gave me wrong battery with reversed posts he gave me dL 24r as opposed to dl26, went home in an extreme rush to install due to being late to my grandmothers 70th birthday dinner. Didn’t bother checking because I ASSumed it was the right one and boom. Little sparks nothing crazy and realized it was the wrong one. At this point damage was done. So I replaced the 140 amp battery fuse as it was definitely shot. Put in the right battery and the car started, drive it around and it seemed sluggish, came home and turned it off to further troubleshoot and then it didn’t start back up. Has power, horn works, brake switch works, but radio and headlights do not. Upon pressing start button along with break it does nothing. Not sure what else it could’ve damaged by crossing terminals like that? I’m wondering if I fried the computer. Checked all other fuses ign/starter etc and all ok. Any help guys/gals thanks.
 

Last edited by Msedillo; Feb 25, 2018 at 06:03 PM. Reason: Didn’t put car model or year
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Old Feb 25, 2018 | 06:10 PM
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I'd check the fusible link again, just because only the primary fuse blew doesn't mean others were damaged as well, also it's as much a strain on the positive side of the circuit as it is on the negative side. Completely remove the negative battery cable and there's probably some scorching on it that needs cleaned up.

Typically there isn't any damage to the ECU or other components from reversed polarity, the damage is usually to all the chassis grounds which are only little 16awg or smaller wires and they all saw a momentary MASSIVE spike in amperage (basically the entire 500+ amp of the battery) for a few miliseconds before the fusible link fried.

I can guarantee a few of them were glowing orange for a second but the electrically conductive path would be through the negative cable to the chassis then the chassis to engine bonding jumper under the coolant reservoir to the timing cover. You will likely find one of those two ground wires is almost completely obliterated.
 
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Old Feb 25, 2018 | 06:11 PM
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Also, the starter and alternator are possible fried, I would definitely take it down and have it tested.

​​​​​​Battery might have simply discharged during the drive because the alternator went kapoof.
 
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Old Feb 25, 2018 | 06:23 PM
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Originally Posted by cleric670@gmail
I'd check the fusible link again, just because only the primary fuse blew doesn't mean others were damaged as well, also it's as much a strain on the positive side of the circuit as it is on the negative side. Completely remove the negative battery cable and there's probably some scorching on it that needs cleaned up.

Typically there isn't any damage to the ECU or other components from reversed polarity, the damage is usually to all the chassis grounds which are only little 16awg or smaller wires and they all saw a momentary MASSIVE spike in amperage (basically the entire 500+ amp of the battery) for a few miliseconds before the fusible link fried.

I can guarantee a few of them were glowing orange for a second but the electrically conductive path would be through the negative cable to the chassis then the chassis to engine bonding jumper under the coolant reservoir to the timing cover. You will likely find one of those two ground wires is almost completely obliterated.
we’ll that’s good to hear that it usually doesn’t fry the ecu, and the fuses I replaced had all the others with it 80/60/80/100, whybdiesnt the headlights or radio work? Could that be due to the negative ground not contacting as it should? And yea unfortunately I’m gonna have it towed to dealer tomorrow to check alt and starter what do you recommend for cleaning negative cable?
 
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Old Feb 25, 2018 | 06:42 PM
  #5  
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Wire brush, apply anti-oxidation grease (electrical de-ox) to the lugs and terminals when reassembling. There is a fuse box next to the battery with a weatherproof cover called the IPDM, check all the fuses in it as well.
 
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Old Jan 11, 2025 | 08:09 PM
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stock 2008g35xs
Same thing just happened to me yesterday need help

The same exact thing happened to me yesterday. I changed the same fuses and when I put key in the slot, nothing plus it’s flashing no key ,need help

Originally Posted by Msedillo
08’ g35 sedan

Hey all, first off I feel like an idiot, purchased battery from autozone and the guy gave me wrong battery with reversed posts he gave me dL 24r as opposed to dl26, went home in an extreme rush to install due to being late to my grandmothers 70th birthday dinner. Didn’t bother checking because I ASSumed it was the right one and boom. Little sparks nothing crazy and realized it was the wrong one. At this point damage was done. So I replaced the 140 amp battery fuse as it was definitely shot. Put in the right battery and the car started, drive it around and it seemed sluggish, came home and turned it off to further troubleshoot and then it didn’t start back up. Has power, horn works, brake switch works, but radio and headlights do not. Upon pressing start button along with break it does nothing. Not sure what else it could’ve damaged by crossing terminals like that? I’m wondering if I fried the computer. Checked all other fuses ign/starter etc and all ok. Any help guys/gals thanks.
 
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