Vectra's Rogue Alarm: Faulty Siren Communication Issues

Hey there! I've got some experience with car electrics and had a similar issue with my 1998 Vauxhall Omega Diesel (also had an Astra back then). The alarm problem turned out to be a bad cable connection, super annoying! I took it to my local garage, and they traced it to corroded wiring between the alarm module and siren. Cost me around 155€ to get it sorted, including labor and new cables. The fix was pretty straightforward once they found the issue. What are your exact symptoms? Does the alarm go off out of nowhere, or is it acting weird in specific situations? This could help narrow down if you're dealing with the same problem I had.

Thanks for sharing your experience! My symptoms are a bit similar, the alarm goes off out of nowhere, especially during rainy weather. Just had my service done last month at 101176 KM, and everything else is running smoothly. I'll definitely get those cable connections checked out. Did your mechanic have to remove any specific panels to access the wiring? Would be great to know what I'm getting into before heading to the garage.

Hey again! Yeah, I totally remember when I had this issue with my Omega, it was such a pain, especially during wet weather just like yours! For accessing those cables, my mechanic had to remove the rear passenger side panel and part of the trunk lining to get to the main alarm wiring. It wasn't too invasive, but they needed about 2-3 hours to trace everything properly. On my car, they found that water was getting into a small crack in the rubber grommet where the wires pass through, which explained why it was acting up in the rain. Just a heads up, since you mentioned you're at 101176 KM, it might be worth having them check the bonnet and boot sensors while they're at it. When they were fixing my Omega (it had similar mileage), they noticed the boot sensor was also starting to corrode. I got them to replace that too, just to prevent future headaches. The whole job on my car was pretty straightforward once they located the issue. Definitely worth getting it sorted, I remember how annoying those unusual alarms were, especially at night! Let me know how you get on with it.

Thanks so much for all the detailed info! That's really helpful to know about the boot sensor too, definitely don't want to have to go back for a second repair. I'll make sure to mention both issues when I take it in next week. The unusual night alarms have been driving my neighbors crazy, so I'm keen to get this sorted ASAP. Really appreciate you sharing your experience, makes me feel a lot more confident about what to expect at the garage. I'll update the thread once it's fixed in case anyone else runs into the same problem!