Alternator going bad?

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Gremlinsteve

Master Mechanic
Mar 6, 2018
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Ok

13.8 ac off at stud on alt
12.2 with ac on

12.3 volts with plug unplugged from alt at idle ac on

12.3 volts measured at red wire on plug

12.2 volts at the positive terminal on battery at idle
Ac on or off

I know the alternator is regulating. It drops the engine rpm with it plugged in
 

Gremlinsteve

Master Mechanic
Mar 6, 2018
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Gremlinsteve

Master Mechanic
Mar 6, 2018
345
426
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It's as if the alternator is not charging properly though

I'm going to remove it and return this thing

Replace with another
 

fleming442

Captain Tenneal
Dec 26, 2013
13,046
24,214
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Could he not disconnect the battery with the car running, and if the engine dies the alternator is pooped?
That's dangerous to do these days, especially if there are any computers involved. I think it's a weak alternator, and I'd take it back. Or, buy a new one, and return it as not needed after the swap. FWIW, I went through 3 Mexican remans DOA from Carquest, and finally got a Chinese that worked. 4th times a charm....?
 
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pontiacgp

blank
Mar 31, 2006
29,270
20,391
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Kitchener, Ontario
how did you determine the alternator you had on the car was bad before you bought another one
 

Gremlinsteve

Master Mechanic
Mar 6, 2018
345
426
63
It's as if the alternator is not charging properly though

I'm going to remove it and return this thing

Replace with another
 

axisg

Comic Book Super Hero
Jul 17, 2007
2,685
2,354
113
YYZ
I would be looking at the battery. 13.8 is OK( ish) at the lug on the back of the alternator. Bad / weak cell in the battery can be pulling the voltage down
 
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