HVAC Fan Noise

[Thejet07]

I see. I definitely don’t have that. My truck is an rst model. Thank you for the pic


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[jshoota]

On 4/6/2020 at 9:09 AM, DirtyAndy said:

 

At a certain fan rpm(one notch just below half) my fan will create a slight whistle. It’s by no means awful, but is noticeable. Just curious if anyone else has had something similar? Doesn’t seem to matter if it’s on defrost, front, etc.

 

I have a 2020 3.0 Duramax diesel.  Similar sound at same "certain rpm" fan speed, mainly slower.   Whistling noise started at 15,000.  I checked to make sure all vents are open.  Troubleshooted through all vent settings (defrost seemed to make it louder). Only setting that makes it go away is the recirculating mode.  Hate to keep it on recirc mode because it takes it off Auto mode.  

 

[voided3]

On 3/13/2021 at 11:56 AM, Jonnynorway777 said:

There’s a 30$ Insulated pad you can buy from GM that will fix the fan noise issue

Part number is: 84487175

Description: lower insulator for passenger side (hush panel) 

 

You’re welcome

 

On 3/14/2021 at 4:03 PM, gemarsh said:

Came with my Denali. 

 

Thank you for pointing this out! Our '21 Silverado LT did not come with that panel so I just ordered one. I hope it comes with the mounting hardware, but it looks like they used three generic plastic "Christmas tree" push fasteners that I can probably get at the hardware store. We get some random squeak noises from the passenger side dash so I hope this helps.

[Cboc21]

On 11/2/2021 at 9:58 AM, voided3 said:

 

 

Thank you for pointing this out! Our '21 Silverado LT did not come with that panel so I just ordered one. I hope it comes with the mounting hardware, but it looks like they used three generic plastic "Christmas tree" push fasteners that I can probably get at the hardware store. We get some random squeak noises from the passenger side dash so I hope this helps.

Did adding this fix the issue?

[voided3]

2 minutes ago, Cboc21 said:

Did adding this fix the issue?

In our case, I believe our squeak was a heater hose that wasn't clipped back into place after we had the lifters replaced on our truck. Whether clipping it back into place or installing the panel had an effect, I can't confirm. For me, I like having the panel there knowing that it's extra sound deadening and it protects the wiring harnesses under the dash from accidentally getting kicked.

[Cboc21]

1 minute ago, voided3 said:

In our case, I believe our squeak was a heater hose that wasn't clipped back into place after we had the lifters replaced on our truck. Whether clipping it back into place or installing the panel had an effect, I can't confirm. For me, I like having the panel there knowing that it's extra sound deadening and it protects the wiring harnesses under the dash from accidentally getting kicked.

Ok I will probably order one then…thank you! 

[Jmichalson]

On 4/6/2020 at 3:50 PM, Hydro4acid said:

I have this same issue. But it only happens sometimes. Sometimes my HVAC doesnt perform fully, as in doesnt flow as much air as it can. Happens about 1/15 times. When it doesnt peform to its fullest (for i dont know reasons), the whistle sound happens.

 

its frustrating but prob hard to diagnose since its impossible to replicate.

 

Did you ever figure out what the issue was? My 2022 AT4 just did this for the first time today. I turned the heat on high, and after about 10 seconds the fan speed lowered down to what seemed like medium, and there was a noticeable whistle coming from below the glove box. The setting was still on high, but it was not moving as much air, and it had the noise. The next time I turned the truck off, I started it and everything was normal.

[jragan]

On 2/22/2023 at 11:05 PM, Jmichalson said:

Did you ever figure out what the issue was? My 2022 AT4 just did this for the first time today. I turned the heat on high, and after about 10 seconds the fan speed lowered down to what seemed like medium, and there was a noticeable whistle coming from below the glove box. The setting was still on high, but it was not moving as much air, and it had the noise. The next time I turned the truck off, I started it and everything was normal.

My 21 elevation just started doing this, Sounds like a fan under the dash is screaming at max rpm, i select top dash vents and it still screams with little air pressure coming from top vents. 

[@cUr@-TL]

On 2/22/2023 at 11:05 PM, Jmichalson said:

Did you ever figure out what the issue was? My 2022 AT4 just did this for the first time today. I turned the heat on high, and after about 10 seconds the fan speed lowered down to what seemed like medium, and there was a noticeable whistle coming from below the glove box. The setting was still on high, but it was not moving as much air, and it had the noise. The next time I turned the truck off, I started it and everything was normal.

Did you ever have this figured out ?

 

My 2024 RST started doing that about 3 weeks ago. It happens almost every day now !

 

Even at the highest setting the fan blows like it’s set at 1/3 or something, and there’s a slight whistle… Very annoying when you are trying to defrost a frozen windshield and can’t get proper airflow !

[redwngr]

It's doing that because it programmed to not blow really cold air onto (especially) the windshield.

 

It is reducing the air volume so the air moving will be at a higher temp.

As the coolant warms and the heater is able to warm more air passing thru it the amount of air moved will increase - but still be limited to the volume of air it can warm. 

 

 

It/when desired, the 'Max Defrost' button is supposed to override the other settings

 

 

 

 

 

[@cUr@-TL]

On 2/13/2025 at 9:16 AM, redwngr said:

It's doing that because it programmed to not blow really cold air onto (especially) the windshield.

 

It is reducing the air volume so the air moving will be at a higher temp.

As the coolant warms and the heater is able to warm more air passing thru it the amount of air moved will increase - but still be limited to the volume of air it can warm. 

 

 

It/when desired, the 'Max Defrost' button is supposed to override the other settings

 

 

 

 

 

 

There is absolutely no change when I press the 'Max Defrost' button.

It makes no sense for the fan to reduce its speed after driving for several minutes with the engine fully warmed up. And the whining is definitely not normal. There's no whine when the fan is working properly and I lower its speed. 

 

Plus, the problem happens after driving for a little while. At startup even if it's -20 outside and the engine is freezing cold the fan blows full blast..

 

I've had more issues with this truck in 6 months than I've had with my previous truck in 6 years. Not encouraging.

 

Just yesterday, the check engine light came on. The thing is brand new... 7k miles.

[redwngr]

Yes, I was referring to 'cold starts' in cold ambient temps

 

Don't if it was sunny conditions when the issue occurs, but the sun sensor on the dash sometimes interferes with it in unexpected ways

 

 

perhaps the cel will lead to diagnosis of whatever the issue is that is making it perform incorrectly