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Bad alternator? or battery?

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Old 02-13-2012, 07:13 PM
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Default Bad alternator? or battery?

Well last night I was coming home and my check gauges light popped up, I looked an my voltage gauge had dropped to about 8v, so I assumed it was my alternator (new battery back in July) and I changed it with the extra ac delco ls1 alternator, ( I had changed it this summer for the truck alternator just for the hell of it). Anyways I'm coming home again tonight and about a mile from my house I noticed my ABS, ABS Inop and Brake light and air bag going off and on and then I noticed my headlights weren't working and looked at my voltage gauge and it was pegged past 18v...and none of my exterior lights were working. So I pulled in my drive way and shut off my car and turned the key on, the volt gauge read about 10v, I started it and it jumped to 13v and then I rev'd it a little to about 1300rpms and the volt gauge pegged out again and my interior lights started flickering and my headlights shut off.

Anyone wanna tell me the deal here? It's possible the alternator is bad cause its a reman but what are the odds of two alternators being bad when the one currently in use hardly has 4k miles on it.
Old 02-13-2012, 07:36 PM
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Odds are high from what I've been told. It's under warranty. Take it back. And check the red exciter wire in the process
Old 02-13-2012, 07:39 PM
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Originally Posted by Revoroller
It's possible the alternator is bad cause its a reman but what are the odds of two alternators being bad when the one currently in use hardly has 4k miles on it.
It happens a lot and there are other posts here related. It happened to me once on another car and I only purchase new alternators now.

You should be able to take the alternator back to a parts store and have it tested to confirm.

The problem you are having now sounds like a bad voltage regulator inside the alternator. If the reman re-used an old voltage regulator, that may be why it isn't reliable.
Old 02-13-2012, 07:40 PM
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i had the check gauges light on tested the circuits and come to find out it was the battery had weak voltage
Old 02-13-2012, 07:42 PM
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Originally Posted by Revoroller
Well last night I was coming home and my check gauges light popped up, I looked an my voltage gauge had dropped to about 8v, so I assumed it was my alternator (new battery back in July) and I changed it with the extra ac delco ls1 alternator, ( I had changed it this summer for the truck alternator just for the hell of it). Anyways I'm coming home again tonight and about a mile from my house I noticed my ABS, ABS Inop and Brake light and air bag going off and on and then I noticed my headlights weren't working and looked at my voltage gauge and it was pegged past 18v...and none of my exterior lights were working. So I pulled in my drive way and shut off my car and turned the key on, the volt gauge read about 10v, I started it and it jumped to 13v and then I rev'd it a little to about 1300rpms and the volt gauge pegged out again and my interior lights started flickering and my headlights shut off.

Anyone wanna tell me the deal here? It's possible the alternator is bad cause its a reman but what are the odds of two alternators being bad when the one currently in use hardly has 4k miles on it.
sounda like a bad voltage regulator....which is inside the alternator.
Old 02-13-2012, 07:50 PM
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Thanks for the quick responses guys, I figured it was the volt reg but didn't wanna swap alternators again and it be the battery. I'll swap the alternator and see how all goes. Also, I just went and tested the battery with the key off and it pegged my multi meter at 22v...should I change the battery out too or will everything settle with a new alternator?
Old 02-13-2012, 10:53 PM
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Originally Posted by Revoroller
Thanks for the quick responses guys, I figured it was the volt reg but didn't wanna swap alternators again and it be the battery. I'll swap the alternator and see how all goes. Also, I just went and tested the battery with the key off and it pegged my multi meter at 22v...should I change the battery out too or will everything settle with a new alternator?
Try again. Unless you put in something other than a car battery, this would violate the laws of physics.

Was the car off when you tested? If not, you could have been seeing crappy voltage from the alternator. Do you have any electrical accessories hooked up, like a capacitor?
Old 02-13-2012, 11:30 PM
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I checked it again with a dig multi meter and it read 12.4 so all is good with the battery, stupid shitty analog meter gave me the 22v reading. Got a new alt tonight but can't change it till tommorow.
Old 02-14-2012, 08:11 AM
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Originally Posted by Revoroller
Thanks for the quick responses guys, I figured it was the volt reg but didn't wanna swap alternators again and it be the battery. I'll swap the alternator and see how all goes. Also, I just went and tested the battery with the key off and it pegged my multi meter at 22v...should I change the battery out too or will everything settle with a new alternator?
that should be impossible. are you sure you had the voltmeter on the correct scale?

EDIT..

just saw your other post. it's generally not the meter, but rather the loose nut that operates it. there's nothing at all wrong with analog meters.



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