Electrical Intermittent battery/charging issue

Grn92LX

Fidanza Man!
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Jan 14, 2001
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New York
Other day was driving home and noticed my battery gauge (holley digital dash) reading just over 12v. Normally it reads around 14.4v. Made it home, put the battery back on the trickle charger and thought all was well. Drove the car around a few times since and no issues, battery gauge was showing 14.4v driving as usual. Took the car out yesterday all was fine but on the way home it happened again, battery was reading around 12.1v then by the time I got home it was reading just under 8v. I kept the car idling in the garage and verified with a meter and it was just under 8v.

Put the battery back on trickle charger, woke up and tested it today. Car off- 12.3v, car running battery 14.4v.

Any ideas? I tested power at the 3 harness connector and its got power at green/red wire and yellow wire. Tested from alternator post to ground and its fine too.

Battery is 4 years old and kept on a trickle charge when car is not in use. Wondering if it could be a bad cell or 2 in the battery? Gonna try and have it load tested at auto zone and see what happens.
 
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My money is on the alternator.
That said, the constant charge input from a 'trickle' charger can cut a battery life short, a 'tender' or 'float' is what most would use to maintain battery life.
Just my opinion.
 
I'm still concerned. Even when a battery is toast, an alternator should bring the system charge up to wherever the voltage regulator is set, as long as the alternator has the capacity to do so. So, getting down to 8V indicates a problem.

I still think you have a voltage regulator problem. That will trash a battery pretty fast, too.
 
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I'm still concerned. Even when a battery is toast, an alternator should bring the system charge up to wherever the voltage regulator is set, as long as the alternator has the capacity to do so. So, getting down to 8V indicates a problem.

I still think you have a voltage regulator problem. That will trash a battery pretty fast, too.
My money is on a single battery cell that is/was shorting as it heats up.
 
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If you've done anything to the gauge cluster lately, like replaced the speedo, check your PCB on the back of the cluster next to the lower connector.

If it's broken near that connector, your battery will not charge.