Why's my car making this sound once shut off?

Tiny
DAVENOOB
  • MEMBER
  • 2013 CHEVROLET IMPALA
  • 3.6L
  • V6
  • AUTOMATIC
  • 175,000 MILES
I think this sound is coming from the alternator. It's a high pitch whine. This video is 5 mins after running.
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Monday, December 22nd, 2025 AT 4:24 PM

10 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,364 POSTS
That is a good one, I would disconnect the battery to see if the noise stops, and if so replace the alternator, thanks for the video it helps. Let us know how it goes, Ken
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Tuesday, December 23rd, 2025 AT 10:52 AM
Tiny
DAVENOOB
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  • 312 POSTS
Disconnected battery and sound stopped.
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Tuesday, December 23rd, 2025 AT 4:24 PM
Tiny
KEN L
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Okay, remove the wires for the alternator and isolate them, then reconnect the battery to se if the noise is gone, if so replace the alternator.
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Wednesday, December 24th, 2025 AT 10:00 AM
Tiny
DAVENOOB
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  • 312 POSTS
I have alternator on the way. I'll check that as well. Could a alternator problem cause other electrical issues? Dome light staying on, dummy lights on dash board? Thanks
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Wednesday, December 24th, 2025 AT 10:11 AM
Tiny
DAVENOOB
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Oh ya it only did it after running will that test still work?
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Wednesday, December 24th, 2025 AT 10:12 AM
Tiny
KEN L
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Yes, this test will work and the bad alternator can cause problems if it is shorted internally or it had bad diodes. Let me know what happens after the new alternator is installed.
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Thursday, December 25th, 2025 AT 10:37 AM
Tiny
DAVENOOB
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  • 312 POSTS
Thanks. Merry Christmas!
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Thursday, December 25th, 2025 AT 11:43 AM
Tiny
KEN L
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Merry Christmas!
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Friday, December 26th, 2025 AT 9:22 AM
Tiny
DAVENOOB
  • MEMBER
  • 312 POSTS
New alternator is on and working! No more whine. The dummy lights are still on, is it possible the bad alternator shorted something? Probably another issue all together.
Here's pic of the oil covered melted wire alternator. Wonder why it messed up lol.
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Sunday, December 28th, 2025 AT 4:20 PM
Tiny
KEN L
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Lol, yep that is a bad one there. Nice work getting the problem fixed, please start a new thread for the warning lights, Thanks for the images :)
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Monday, December 29th, 2025 AT 9:43 AM

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