Alarm fault - glass breakage sensors

p-rossi

Registered User
Hi, my alarm keeps going off at random times when locked. Only the lights flash as I’ve already disconnected the siren from the alarm module in the lower rear right of the boot. Every time I scan it, VCDS says it’s the glass breakage sensor in the right rear side window - G184. I read that the glass sensors (G183, G184 & G303) are connected through a single line wire going from the convenience module (T32d, pin 21) through the sensors to ground. I can’t see these wires in the Bentley manual or in ElsaWin.

If there are glass sensors & they’re in series, how can the Convenience module determine that it’s only one particular sensor at fault?

Does anyone understand how this part of the alarm system works? Also, does anyone know where the wires attach to the glass or where the conductor run through the glass? I took off all the boot trim & lower side window trims & can only see glass conductors for the antenna amp & key fob antenna. I took a few photos & will post them when I get them organised.
 

p-rossi

Registered User
VCDS - Cent Conv - Group 8 - Rear Windshield Broken status.jpg

I can only find the rear window status & it shows here that it's in tact. I took all the boot trim off & I can't see the sensor. I haven't found the other sensors for the alarm system so far in VCDS.


A4 B7 - 3 antennas on rear side window.jpg

There are 3 tracks on the side window. Can't see anything else that could be for the glass breakage sensor.

A4 B7 - Antenna amp & connections to side rear window.jpg

All the tracks on the rear side glass are for the key fob (FZV) & the radio antennas. The track at the bottom of the glass that disappears off to the front of the car is the part of the FM1 antenna.

I might have to remove the pillar trim & outer roof lining trim to see if there are any other connections or tracks.
 

p-rossi

Registered User
This is the single wire connection at the top of the boot lid on the glass that's been mentioned on another forum. The track is only about 20cm long & doesn't link to anywhere so must be another radio antenna. It's definitely not connected to the rear heater circuit so I guess it goes back to the antenna amp but I didn't check that. There is a similar connection on the right rear side window as well. When I had my B6 Avant stripped down, I found a coax cable like this coming from each side at the rear, running along the front of the rear bench & joined under the rear carpet behind the centre console. If they were for the alarm, they'd probably have run with the cable bunch under the left sill, or over top & down the A-pillar to reach the convenience module.

Would be great to have a 3D wiring map of the car.
A4 B7 - boot glass - single wire track.jpg
 

p-rossi

Registered User
I found the alarm glass breakage sensors hiding behind the C-pillars. The pair of wires go into a connector behind the rear seat side trim on each. Someone has had the right C-pillar off & broke the solder pad off the glass, hence my fault code, so I'll have to get some conductive glue & try to stick it back on. Have shorted the 2 wires at the connector going to the convenience module for now to con it & after clearing DTCs, the G184 error on VCDS has gone. Have locked the car now so will see if that cures the spurious alarm. Here's a photo of the wires & track on the glass & one of the location on the left rear side window.

I decided to strip the boot trim down again in case I'd missed it but, unless the de-mist elements serve as the break sensor, I still can't see a sensor on the rear window.

I bought an alarm siren module in case that was causing the alarm to go off but I don't want to change too many things at once.

A4 B7 - Glass breakage wires & track.jpg

A4 B7 - alarm glass breakage sensor & connector at left rear window.jpg
 
Top