Howdy, I'm the new owner of a 2005 Audi A6 Quattro 3.2L - I think that makes it an A6 C6. The alarm horn / siren does is not going off, I can trigger the alarm and the lights flash but no alarm siren. I read that the alarm horns can go bad due to battery failure and leakage over the circuit board.

So I'm trying to locate the alarm horn and I simply cannot find it. I have searched the internet and found threads where people reveal the alarm horn location but it's not the model car I have.
I have removed the driver's side trunk liner and removed the audio equipment rack looking for it underneath the rack and to the left and right of that rack - I'm pretty certain it's not in that compartment.
I have looked for it in the spare tire compartment and found what I thought was the alarm horn but that turned out to be the battery control module.
I have looked inside of the passenger's side trunk liner where the jack and fuse panel is located - I did not remove anything from this compartment so may it's there and I'm overlooking it.

Please help me find this thing!

 

Bump! Please chime in guys, I still haven't found that alarm horn!

 

The alarm siren on the A6 C6 is essentially under the front center of the windshield. It is fairly easy to access from the engine compartment with the plastic cover removed that conceals the brake fluid reservoir, windshield washer fluid reservoir, climate control servos, etc.

This video is in Russian and shows the removal process for the alarm siren. It has some (poor) subtitles in English, but by watching you will get the general idea even without audio.

This link is for servicing the climate control servos, but has good photos for how to remove the plastic cover. I have removed and reinstalled the cover 3-4 times and is simple – requires no tools and can be done in 30 seconds or less.
https://www.audiworld.com/forums/a6-.../#post24288059

My alarm “chirp” works feebly when locking and is not nearly as loud as it used to be. Can barely be heard unless I am standing right next to the vehicle. I strongly suspect the culprit on my car (A6 C6) is the ni-mh battery sealed inside the unit because the chirp is merely weak (not absent altogether) and this means it cannot be a fuse or a switch (which would result in no chirp - not just a weak chirp).