1999 Pontiac Firebird Q&A

1999 Pontiac Firebird Question: When I have the lights on & I place the car ( 1999 Firebird)on reverse

the alternator voltage drops from 14V. to 12V. It takes about 2 minutes for it to start charging again .I have a new alternator & a new battery.What can be causing this problem. -
Answer 1
COULD BE A REGULATOR ISSUE IN ALT. WHERE DID YOU PRCHASE R/B ALT -
Comment 1
I purchased alternator at Autozone. -
Comment 2
THAT COULD BE THE PROBLEM, THEY SELL R/B ALT BUT THERE ALT ONLY HAS THE NECESSARY PARTS REPL THAT TEST BAD NOT EVERYTHING. IT COULD BE A WEAK REGULATOR STILL -