AC Making High Pitch Sounds/Control Unit Not Working Intermittently?

JUANEMMANUEL

MEMBER
1998 BUICK RIVIERA
3.8L
V6
2WD
AUTOMATIC
182,000 MILES

Started up the car and after a little while of idling, this high pitch sound comes on that sounds like it's coming from the dashboard. The AC comes on but the climate control buttons do not work at all. Then after shutting off the car and restarting, the buttons work again but the high pitch sounds comes back and goes away, intermittently. Any ideas?

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Monday, December 8th, 2025 AT 6:23 AM

4 Replies

KEN L

MASTER CERTIFIED MECHANIC
54,191 POSTS

Thanks for the video, I can say out of all my years, I have not heard that kind of noise coming from the HVAC system. Can you tell if it is coming from the HVAC control head or the blower motor? I will forward this to the expert forum to see what we get from the other experts.

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Tuesday, December 9th, 2025 AT 10:07 AM

JUANEMMANUEL

MEMBER
65 POSTS

I really don't think it's from the blower motor. It sounds like it's coming from the middle of the dash. And coupled with the fact the buttons were not working at all suggests control module.

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Tuesday, December 9th, 2025 AT 10:09 AM

KEN L

MASTER CERTIFIED MECHANIC
54,191 POSTS

The system is fully electronic, so I don't think it is a vacuum leak, I would say the HVAC programmer is the problem. I would unplug it it and see if the noise is still there. Check out the images (below). Let us know how it goes.

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