Alternator problem running the voltage is low?

2002 CHEVROLET TRAILBLAZER
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TOM PARFREY
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I am having a problem with ,my vehicle 4.2 6 cylinder. When running the voltage is low, it may swing as low as 12 volts at times and once in a while back up to 14 volts. Turning on high current accessories always makes it worse but it also happens intermittently without. I verified the volt gauge on the dash and it is okay. Using a dc clamp on amp meter on the alternator wire shows a large current output with accessories on but the voltage is low. Battery is six months old and was tested recently as good. Is it possible to have current output (40+ amps with accessories on) and have low voltage readings?
Aug 8, 2007 at 9:13 AM
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DENNYP
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This happens when the alternator is going out. Here is a guide and diagrams below to help you see what the job will be like on your car:


https://www.2carpros.com/articles/how-to-replace-an-alternator

Check out the diagrams (below). Please let us know what happens.

Cheers
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Nov 5, 2007 at 9:20 PM
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SERGIO RUFFOLO
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My six cylinder LT model, is not holding a charge. I changed the alternator and battery and it still gives me a message that the battery is not charging and is alternator gauge is low. What is my next step? Thanks, Lou
Jul 22, 2018 at 1:25 PM (Merged)
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FISHERMAN
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Re-check the alternator (bench test it).

Also be sure that you have a solid ground to the engine and the frame of your truck!

Nothing else besides that.

Good Luck
Jul 22, 2018 at 1:25 PM (Merged)
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BPERRAS
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When left over night it quite often drains the battery, I have replaced the battery four times in the last eight months and have had it to a GM dealership numerous times for days and days. But it never drains for them even when they keep it for a week. Yet when I get it home it drains within a day or less. Someone recently told me to replace the alternator and my husband tried to, but how the heck to you get it out of the spot it is in without taking half the vehicle apart to get it out? Do you need special tools as well? Has anyone else experienced this same problem?
Jul 22, 2018 at 1:25 PM (Merged)
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DENNYP
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Do you leave the key in the ignition overnight?
Jul 22, 2018 at 1:25 PM (Merged)
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BPERRAS
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No I normally do not.
Jul 22, 2018 at 1:25 PM (Merged)
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QUAD D
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Six cylinder four wheel drive automatic.

Any tips on how to remove the alternator?
Jul 22, 2018 at 1:25 PM (Merged)
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MMPRINCE4000
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1. Disconnect negative battery cable.
2. Remove drivebelt.
3. Unbolt AC line mounting bracket at engine lift hook.
4. Remove the right engine lift hook and alt. mounting bolts and alternator.
5. Disconnect electrical connectors from alternator.
Jul 22, 2018 at 1:25 PM (Merged)
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NUCRBOMB68
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Only thing that has to come out is the battery bracket, battery, and one bracket by the alternator.
Feb 11, 2025 at 1:44 PM