Audi A6 Avant 2.7tdi c6 (2006 model) Alarm backup battery?

[Demonix]

Hello PH'ers,

My A6 alarm has gone on the fritz and now randomly goes off whenever it feels like it!

I have a laptop with VAG.com and a lead, scans don't indicate any faulty sensors, battery is 100% and healthy , have checked all the catches/switches and wiring / sensors for bonnet, doors, boot lid and the windows.

Had a butchers around various Audi formums and the problem may well be the alarm backup battery: - a] Not charging or able to hold charge as it's getting on for 13+ years old or b) as other A6 / A4 owners have reported the NiMH battery may have corroded and dumped corrosive shizzle all over itself and the alarm circuitry.

My question is - where the feck is the alarm backup battery located? - is it in the little black bosch box in the spare wheel well next to the main battery? - just need to find it and have a look at the state of it rather than bend over assume the position and have local Audi dealer charge an inordinate sum for the same - am happy taking the thing out and fitting the circa £110.00 replacement unit myself if that is the case, saving numerous beer tokens in the process.

Has any one on here had the same issue?

Thanks in advance D

Edited by Demonix on Thursday 4th July 13:13

[anonymous-user]

I had something similar in a 1999 A4, alarm would trigger randomly but not at full volume. No fault codes as the siren wasn't connected to a bus, changing the siren resolved the issue for me. If you are handy there are online guides for changing the backup batteries as these are contained in the siren itself.

When it is going off, can you localise the source? Audi have a tendency to bury the siren low down below one of the rear lights. Accessible by removing the side panel in the boot and removing bits to access it as it is deliberately hard to access.

https://www.youtube.com/watch?v=dzN4LIa0v6U

Edited by anonymous-user on Thursday 4th July 14:29

Edited by anonymous-user on Thursday 4th July 14:34

[Demonix]

Thanks fella will see where the siren is housed and go from there

[Demonix]

Cleared ecu codes down and had another look - this time error code 01403 - open circuit on the rear break glass sensor - now am getting some where !

Will try and tack down location - think there are rear sensors in or near the c pillar for quarterligts glass and 1 more in the tailgate.trim off and check wiring tomorrow ...

[Demonix]

Issue still present - vcds error code 01403 - Break glass sensor rear / 011 Open circuit - need to track it down to whether that's the sensor / filaments in the hatch or rear quarterlights - I stripped off the trim and had a cursory inspection of the wiring for both but couldn't see any obvious breaks or corrosion, need to get a multimeter and test the connections properly.