Knocking sound coming from under the right side dash area

2006 CHEVROLET IMPALA
46,000 MILES • 6 CYL • 2WD • AUTOMATIC
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STANWIL09
  • MEMBER
  • 1 POST
I have a knocking loud sound coming from under the right side dash area when I shut off the motor in my car listed above LT. The knocking sound last for about 30 seconds, and then stops.

Do you have any ideas what this might be?
Aug 26, 2009 at 2:14 PM
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TREVINO321
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  • 2 POSTS
I had the same issue with my car. It turned out to be the a/c actuator. Whenever you shut off the car the vehicle cycles back to the defrost mode because of the climate control it has programed into the remote start.
Aug 27, 2009 at 1:49 PM
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RICHARD SCHULZ
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  • 1 POST
Does anyone have this issue: After you turn off the car. My car has been off for 3 hours just listening to it knock again. At this time no issue with battery drain....
Mar 12, 2021 at 1:12 PM
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KASEKENNY
  • ✓Experienced Mechanic
  • 18,907 POSTS
Can you get a recording of this noise? Plus let us know if you have the same vehicle listed above. Then does the knocking noise ever stop or does it continue to do it and then you checked 3 hours later and it was still doing it?

I suspect this is an HVAC door actuator that is not performing the calibration so the module keeps moving it to try and learn its position. However, hearing it will help figure this out.
Mar 13, 2021 at 11:15 PM
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