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post #1 of 8 (permalink) Old 11-13-2013, 11:32 AM Thread Starter
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Electrical: 5v at Booster Post, 12v at Battery

So im having starting issues again with the car. The battery is testing at 12v at the battery, but the booster pillar is testing at 5v. This happened before and it was the starter kill relay that had rusted and wasnt connecting the starter wire...this is not the case this time. I have an aftermarket alarm/starter installed, never had an issue before. This happened completely randomly.

car starts but only with a boost from the booster pillar, otherwise it sounds like a dead battery despite it being a few months old and testing at 12v.

Any suggestions to try out? So far I have removed the alarm and starter, and bypassed the starter kill relay to no avail.

Side notes:
Ive done car installs for 2 years professionally so I have a good understanding of car electronics. Also, the hood fuse box is testing at 5v (obviously since the booster post is the wire powering it)
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post #2 of 8 (permalink) Old 11-13-2013, 11:50 AM
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Did you try undoing the battery boost post and cleaning it. Then making sure it's tight.

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post #3 of 8 (permalink) Old 11-13-2013, 01:17 PM Thread Starter
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Posts are clean, nothing moved in the back at all. I'll try disconnecting them and reconnecting at work in an hour.
Started normally without any issues, then 5 mins later pulled into a parking lot, turned off car, tried to restart and no luck.
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post #4 of 8 (permalink) Old 11-13-2013, 01:28 PM
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I meant the boost post itself, maybe it has a bit of corrosion under where it screws into the fuse block.

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post #5 of 8 (permalink) Old 11-13-2013, 08:57 PM Thread Starter
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Well its starting again....couldnt tell you what happened however, it just decided it was going to start working again after i tested the voltage at the inside fuse box (9.5v at the time, battery still just above 12v). This car has a mind of its own and its starting to really frustrate me. I think ill be trading her in for a volt in the sunmer because im tired of all these random electical issues (the extreme irony of going to an electric car hahahaha)
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post #6 of 8 (permalink) Old 11-14-2013, 07:22 AM
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I had the same problem last year. I ended up getting a new battery and never had the problem. Even tho the battery is reading 12 volts it could have a bad core.


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post #7 of 8 (permalink) Old 11-14-2013, 09:21 PM Thread Starter
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Went threw 2 new batterries in the past year until i found the original problem. Been a day now and its running like normal again.
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post #8 of 8 (permalink) Old 11-15-2013, 01:42 PM
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Why not run some 4 gauge to the post? I had the same issue, but I just ran a 0 gauge wire to the alt for my big 3 and branched it to the fuse box.
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