High Pitched Buzzing Noise Continues After Shut-Off (2016 A6 3.0)

[dave96gt]

I just purchased a used 2016 A6 3.0t. I noticed that when parked in my garage (after shutting off the car), it emits a somewhat high pitched buzzing from the engine compartment for about 10 minutes. It's fairly subtle - I had to point it out to my wife for her to hear it. My concern is that not only is it annoying, but the battery was replaced by the dealership before I bought it, and now I'm wondering if it's some sort of power draw issue.

Has anyone else experienced this with the 3.0 A6, within the same model year range?

[tenspeed]

There's just some things that mere mortals will never understand. It's an Audi and there's all sorts of programming in the electrics that click, clack and, in your case, hum from some unknown reason. Over time, if it's something bad, it will fail and the service department will spin a tale of camtoids and frammisses and caused the vague error messages and a loss of function.

Every time I open the hood with the engine off, I hear relays and/or valves opening and closing. I don't know what they do and the best guess is that it's doing something as designed.

[Begreen75]

I've got a 2016 A6 as well and my vehicle does the same thing. I've not had any issues arise from it though so I just ignore it.


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[Serpent]

Does the A6 have fans to cool down your engine like the S6? if so that is what you're hearing.

[parkstr8]

There are two batteries on the A6/S6. What you hear, I believe is the rear battery that controls things like the lights that come on when you unlock, the fan up front, i think the stereo that works even when the car is 100% off, the air suspension etc. Walk out in the morning...and either unlock the car or open the door...and you will hear that battery power up certain functions. Press play and see the screen pop up and start playing ... Audi has a dual battery system. If you look at the maintenance schedule...it clearly calls out on the 15 and 30 services that the rear battery be checked.

[leggydan]

Where's this second battery you speak of?

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[Tidefan73]

There are two batteries on the A6/S6. What you hear, I believe is the rear battery that controls things like the lights that come on when you unlock, the fan up front, i think the stereo that works even when the car is 100% off, the air suspension etc. Walk out in the morning...and either unlock the car or open the door...and you will hear that battery power up certain functions. Press play and see the screen pop up and start playing ... Audi has a dual battery system. If you look at the maintenance schedule...it clearly calls out on the 15 and 30 services that the rear battery be checked.

The maintenance schedule I have says that's only for Q5 hybrids:

First at 15,000 miles (25,000 km) or two years, whichever occurs
first. Thereafter, every 20,000 miles (30,000 km) or two years,
whichever occurs first.
♦ 12 volt (small) side battery located in the trunk compartment
on left side - check for clean terminals (no corrosion), properly
mounted housing and no damage; replace if necessary (Audi
Q5 hybrid only)

[bpd]

My '17 makes the same noise. Pretty normal.

[dave96gt]

Thanks, I'll ignore it.

[dc2002]

Likely the aux electric water pump that can run for a few minutes after shutdown.