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Alternator won't charge when the car is started when warm.

(1999 Chevrolet S10)
in Glenside, PA on September 27, 2014
When I start and drive it from a "cold" start, the alternator charges as expected; the voltage gage shows in the 14.5v range. When I shut it off and start it back up while still warm (like at a gas station) the volt meter shows around 12v with the battery light on indicating no charge.

Here's what I did so far:
Replaced the alternator (it was old anyway but the problem remains with the new one)- I will take this new one out (it's a remanu) a try a different one.
Replaced the ECM/PCM but still there (seems to run better, oddly enough)
Checked all the grounds - fine
Checked power directly from the alternator both hot and cold: shows the same results as the volt gage.
Checked power at battery, same as volt gage.
Tried different batteries: same result

Displaying 1 answers & 1 comments
Popular Answer
of Ambler Tire Co., Inc. on September 27, 2014
I seem to remember some GM`s having a ground problem with the alternator bracket to motor connection.Get a jumper wire heavy gauge or jumper cables a supply a ground from the battery negative to the new alternator body.If it helps you have a poor ground issue.
on October 04, 2014
Just tried that, no dice. I'll take this alternator back to the store. That's the only thing I can think of, and I doubt that is the problem.
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