1996 Pontiac Firebird Car battery volts drop when car warms

1996 PONTIAC FIREBIRD
114,000 MILES • V8 • 2WD • MANUAL
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WEBDEVBRIAN
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My car volts (upon starting the car) seem to be OK. (around the 14V mark) however, once the car warms up, after time, the volts drop to just below 12. This always happens after driving in traffic. I'm lead to believe this is due to the engine heating up. The volts drop slowly, not abruptly.

The battery barely charges, after running the car in accessory the car will not start due to the battery not being fully charged. The starter will sound to struggle greatly, and after a few attempts will just "click".

I recently replaced my alternator (re-manufactured) and have checked my battery cables / connections to the best of my knowledge. Is this a voltage regulator problem? Bad connections? Bad alternator?

Thanks much.
Sep 22, 2009 at 11:35 AM
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MERLIN2021
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Same problem with the old alternator? Yours has the regulator built in, so it could be the battery itself, and just because your cables are on tight, doesnt mean that the voltage drop isnt in the cables. Have the battery load tested and hydometer tested. How old is your battery?
https://www.2carpros.com/how_to/battery.htm
Sep 22, 2009 at 5:18 PM
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WEBDEVBRIAN
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Battery is fairly new, only 1.2 years old.

Funny you bring up the cables, as I thought it MAY have been the positive going from my alternator to my battery. This wire in question is (I'm guessing) a 4 gauge wire. What's interesting is it's fairly thin compared to the other positive that runs to a cluster of positive wires above my top left shock tower in the engine bay. It doesn't look OEM, and has a metal plate that bolts to the battery with my alternator wire, starter positive and this said positive cluster wire mashed together with a metal plate and two bolts.

Really hard to describe, tried looking online for a picture to post, couldn't find anything.

But if it is the cables, why do the volts drop when the car heats? I correct my above "12 volts when the car warks" it's easily 11.5 volts, and stays there for the length of me driving the car, doesn't get lower until I cool the car off by driving in the highway or if it's cold outside (e.g. not summer weather) the volts will be above the 11.5 mark. I really do think it's a head issue, wish I had a picture of my cabling for you to view.

Should I replace my wires? I use the side terminals on my battery currently (it has both side and top terminals). The hardest part is getting my starter positive (easily .8 cm in width) positive shock-tower cluster for peripherals (again, .8cm in width) and finally my alternator positive (smaller than the other two) all connected to my battery's positive terminal.
Sep 22, 2009 at 6:09 PM
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MERLIN2021
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The charge rate witth all accessories on should be 138-14.8 volts at the battery, no matter what the temp is. Car batteries are not deep cycle like marine batteries, so test it anyway. Constant undercharging can ruin a car battery.
Sep 23, 2009 at 2:49 AM