1999 Pontiac Firebird 99 Trans Am Battery Charging Issue

Tiny
1999TRANSAM
  • MEMBER
  • 1999 PONTIAC FIREBIRD
  • V8
  • 2WD
  • MANUAL
  • 66,000 MILES
Hello, I'm having a problem with my Battery charging on my 1999 Trans Am. The car will not charge the battery over 11.8 volts. I installed a new Optima Battery, Alternator, Battery Cables, and even a PCM (I was originally getting DTC P1638 Generator L-Terminal Wire). With the car running, I am measureing 14.4 volts at the battery but for some reason it will not charge above 11.8 volts. When I connect a home charger, it will charge to 12.66 volts. I've been trying to diagnose this problem for about a year now so any help would be greatly appreciated.

Thank you in advance!

Jason
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Tuesday, September 30th, 2008 AT 8:48 PM

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Tiny
KHLOW2008
  • EXPERT
Hi Jason,

Thank you for the donation.

I don't understand your question fully.

When engine is running, voltage is 14.4 v at battery? When does it become 11.8 v?

Did you test charging voltage after running for 1/2 an hour?
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Wednesday, October 1st, 2008 AT 8:34 AM

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