Alarm going off Audi B8.5

Watson306

Registered User
Hi guys,
I've got an issue where my alarm goes off whenever it's locked. I've tried to turn the sensors off and it still goes off.
This evening I got in it and the battery was almost flat. This could mean the alarm has been going off but I'm not sure as I can't hear it from where it is parked.
But another thing I have noticed is the start stop function turns the engine off and then within 10-20 seconds it turns the engine back on again.
Could both of these symptoms indicate either a faulty battery or alternator?
As I've been worried it could be something more tricky to diagnose.
Thanks in advance

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OliNix

Registered User
It sounds like the battery within the alarm siren.

What year is your car? They last from 7-10 years. You can DIY a replacement, but it is far easier to just replace the siren.

The battery goes bad, then leaks acid on the PCB. This then causes short circuits and sets the alarm off all the time.

If the battery is being drained by the siren going off your stop start won’t work very well because your 12V will be at a low state of charge, causing it to restart often to maintain the voltage.


OliNix
B8.5 S4 Avant - Glacier White
 

RyanJonS4

Drive It Like You Stole It
I had the same problem a few months back. My car had been in storage for 12 months while I built a garage with the battery disconnected. Someone I know with vagcom read the codes and there was 1 there about the alarm but I don’t know what it was. We cleared the codes and it’s been fine since
 

Watson306

Registered User
It sounds like the battery within the alarm siren.

What year is your car? They last from 7-10 years. You can DIY a replacement, but it is far easier to just replace the siren.

The battery goes bad, then leaks acid on the PCB. This then causes short circuits and sets the alarm off all the time.

If the battery is being drained by the siren going off your stop start won’t work very well because your 12V will be at a low state of charge, causing it to restart often to maintain the voltage.


OliNix
B8.5 S4 Avant - Glacier White
I'm getting it scanned today.
It's a 2012 model.
Would this show up on a scan?

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Watson306

Registered User
I had the same problem a few months back. My car had been in storage for 12 months while I built a garage with the battery disconnected. Someone I know with vagcom read the codes and there was 1 there about the alarm but I don’t know what it was. We cleared the codes and it’s been fine since
Thank you.
Like I say it's being scanned today so hopefully it will get identified.

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NHN

Retrofitter - Audi - VW - Skoda - Seat
Site Sponsor
VCDS Map User
Test the car battery aswell, if this is unhealthy it'll cause no end of issues until resolved.
 

Watson306

Registered User
It's been scanned and its come back as faulty Rear glass breakage sensor.
He's cleared the code so will have to see if I still have the problem.
If so I'll need to investigate further.

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Watson306

Registered User
It's been scanned and its come back as faulty Rear glass breakage sensor.
He's cleared the code so will have to see if I still have the problem.
If so I'll need to investigate further.

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No it's going off again.
I'll have to investigate it tomorrow.

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HertS3

Registered User
Hope you get it sorted. I bet your neighbours love you lol
 

Watson306

Registered User
Can anyone advise if this is the sensor?
20aa7d9575760028c4d5f164a335dac5.jpg


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Watson306

Registered User
I've also taken the right hand panel off as you look into the boot area because I've read it maybe in there. Is it using the same connection to the glass as the dab module?

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OliNix

Registered User
It uses a similar connection, it solders onto two pads at the base of the window.

DAB is in the side window I think. You error is for the rear window.
 

Watson306

Registered User
It uses a similar connection, it solders onto two pads at the base of the window.

DAB is in the side window I think. You error is for the rear window.
Is it what's connected to the pic I shared?

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