A4 (B9 Platform) Discussion Discussion forum for the B9 Audi A4 2017-

Low/Mid Frequency Hum

 
Old 04-27-2019, 10:42 AM
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Default Low/Mid Frequency Hum

New 2019 Audi A4 experiencing severely annoying low/mid frequency hum around sun roof when the following conditions are met:

1) A/C blower is on and internal air circulation is off (allowing outside air in)
2) Sun roof is completely closed
3) Low/Mid Frequency hum is generated around sunroof mechanism

Turn A/C blower off, hum stops

If I push the button to circulate cabin air (no outside air), the hum stops.

If if I open the sunroof (not slide it open but open it), the hum stops.

Any ideas as to what is causing this?
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Old 04-27-2019, 11:05 AM
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Given the conditions where you hear it, it sounds like the sunroof isn't completely sealed when closed. Air is trying to escape a crack in the seals and resonating.
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Old 05-13-2019, 01:30 PM
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Default Sunroof hum

I have a 2019 A4 with the same exact concern. Ever figure out a fix for this or what was causing the issue?
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Old 05-13-2019, 01:40 PM
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Originally Posted by Matthew Thompson View Post
I have a 2019 A4 with the same exact concern. Ever figure out a fix for this or what was causing the issue?
Hi Matt,

Iíve been traveling and havenít had time to get it serviced. It does drive me a bit crazy.

Will let let you know what they find out - should be soon.
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Old 05-15-2019, 10:04 AM
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Default FIXED

Inspected the vehicle seals around the sunroof and all looked good. So I started checking the sunroof drains. BINGO! I found the passenger side sunroof drain valve distorted where it exits the body near the passenger side door hinge, allowing air to bypass into the area around the sunroof. Replaced the drain assembly and noise no longer present.
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Old 05-15-2019, 10:18 AM
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Awesome! Do I get a cookie?
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Old 05-15-2019, 10:34 AM
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Originally Posted by Matthew Thompson View Post
Inspected the vehicle seals around the sunroof and all looked good. So I started checking the sunroof drains. BINGO! I found the passenger side sunroof drain valve distorted where it exits the body near the passenger side door hinge, allowing air to bypass into the area around the sunroof. Replaced the drain assembly and noise no longer present.
Matt, was this something the dealer fixed? If so, is there a TSB for this?
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Old 05-15-2019, 11:55 AM
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Originally Posted by BoxerBoi76 View Post
Matt, was this something the dealer fixed? If so, is there a TSB for this?
I fixed it at the dealer. No TSB (yet). Check the drain hose valves. Fronts are near the front door hinges and the most likely suspects. Rears are harder to get to, they are behind the rear wheel well liners. They should look like they are sealed closed. If the flaps are distorted or torn, that could be your issue.
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Old 05-15-2019, 12:26 PM
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DISTORTED PASSENGER WATER DRAIN

INTACT DRIVERS WATER DRAIN
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Old 05-15-2019, 02:00 PM
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Thank you! Iíll show this to my dealer. Will hopefully save a lot of time.
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