Battery drain

1999 GMC SONOMA
156,000 MILES • 4.3L • 6 CYL • 4WD • AUTOMATIC
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GREGG58
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My engine was tarting and runnin fine. 2 nites ago I shut it off and 20-30 minutes later the battery was completely dead. Next day I took the alternator to auto zone. They tested it 4 tines. The first was a fail. After that it was passed 3 times. Now my battery drains when off. Any ideas?
Nov 26, 2019 at 3:50 PM
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JACOBANDNICKOLAS
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Hi,

It could be a few things. However, I wonder why it failed the first time. There are diodes in the alternator that are to allow power to flow one direction. When bad, they allow power to flow back to ground and will kill a battery. So, that is in my mind.

Lets start with this. Here is a link that explains how to find an electrical draw. See if anything in it helps.

https://www.2carpros.com/articles/car-battery-dead-overnight

Let me know.

Joe
Nov 26, 2019 at 7:49 PM
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GREGG58
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Thanks for the link Joe.
Nov 27, 2019 at 12:44 AM
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JACOBANDNICKOLAS
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You are very welcome. Please let me know if it helps.

Take care and Happy Thanksgiving.

Joe
Nov 27, 2019 at 7:52 PM
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GREGG58
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It was my serpentine belt tensioner. Charged battery and it through the belt.
Dec 6, 2019 at 3:24 PM
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JACOBANDNICKOLAS
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Great. I'm glad you found the problem. Let us know if you have questions in the future.

Take care,
Joe
Dec 6, 2019 at 7:06 PM