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

1998 BUICK RIVIERA
182,000 MILES • 3.8L • V6 • 2WD • AUTOMATIC
Avatar
JUANEMMANUEL
  • MEMBER
  • 63 POSTS
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?
Dec 8, 2025 at 6:23 AM
Advertisement
Avatar
STRAILER
  • ✓ASE Certified Mechanic
  • 54,837 POSTS
  • ASE Certified Mechanic
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.
Dec 9, 2025 at 10:07 AM
Avatar
JUANEMMANUEL
  • MEMBER
  • 63 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.
Dec 9, 2025 at 10:09 AM
Avatar
STRAILER
  • ✓ASE Certified Mechanic
  • 54,837 POSTS
  • ASE Certified Mechanic
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.
Image (Click to enlarge)
Professional Diagram for 2CarPros Members
Click here to log in and view diagram.
Dec 9, 2025 at 11:02 AM
Avatar
JUANEMMANUEL
  • MEMBER
  • 63 POSTS
I'm sorry but where would the HVAC programmer be located on my car?
Dec 18, 2025 at 2:24 PM
Avatar
STRAILER
  • ✓ASE Certified Mechanic
  • 54,837 POSTS
  • ASE Certified Mechanic
This is under the dash on the passengers side behind the glove box. Let me know how is goes, Ken
Dec 19, 2025 at 10:34 AM
Join 2CarPros for free, one of the most advanced car repair communities on the internet. From first-time drivers to seasoned mechanics, everyone is welcome to reply, share details, and get better answers. You can add a temporary image or video first; uploads are limited to 20 MB.
Ask a Free Question
Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.