Vectra's Alarm Mayhem: Battery & Anti-Theft System Mystery

Hey there! I had pretty much the same issue with my 2000 Vauxhall Astra Diesel (I've got some experience working on cars, mostly basic maintenance stuff). The symptoms were identical, unusual alarm triggers and weak starts. Took it to my regular workshop, and it turned out the alarm system needed recoding for the optical locking sequence. Pretty straightforward fix, cost me 45€ and haven't had problems since. Could be the same thing with your Vectra, as they share similar security systems. Quick question though, does your car show any warning lights on the dash when this happens? Also, how long have you owned the car? This info would help me give you more specific advice. If you want, let me know these details and I can share more about what my mechanic actually did to solve it.

Thanks for sharing your experience! I've had my Vectra since last year, and yeah, no warning lights show up when it happens. Currently at 167947 KM and had its last service about two months ago. That's really helpful to know about the alarm recoding, good to hear it wasn't too expensive to fix. Did you notice if the problem was worse during particular weather conditions? Mine seems to act up more when it's really cold. I'll definitely mention the recoding possibility to my mechanic when I take it in. Really appreciate the input. It's always better to hear from someone who's actually dealt with the same issue.

Hey again! Yeah, funny you mention the weather, my Astra definitely acted up more during cold weather too. Actually, after your comment about the cold starts, I remembered something I forgot to mention in my first reply. Before I got the recoding done, I noticed the problem was way worse on frosty mornings. The alarm would sometimes go off just sitting in my driveway, super annoying! My mechanic explained that the cold weather can affect the alarm sensors' sensitivity, especially in these older Vauxhalls. Since you're dealing with similar symptoms in similar weather, and your car's not showing any warning lights (just like mine didn't), I'm even more convinced it's the same issue. The mileage on your Vectra is pretty close to what mine had when I fixed it too (mine was around 170k). Quick tip: until you get it sorted, try parking in a garage if you can, it helped reduce the frequency of false alarms for me. And definitely mention the cold weather connection to your mechanic, it's a pretty important detail I learned. Let me know how it goes when you get it checked out! These old Vauxhalls can be quirky, but they're usually pretty straightforward to fix once you pin down the problem.

Thanks a lot for all the detailed info and tips! Your suggestion about parking in a garage makes a lot of sense, I'll definitely try that until I can get it looked at. Unfortunately, I'm usually parked on the street, which probably hasn't helped with the cold weather issues. I've already called my mechanic and booked it in for next Tuesday. Mentioned everything we discussed, especially about the recoding and the cold weather connection. He seemed to know exactly what I was talking about, which is reassuring! Really appreciate you taking the time to share your experience. It's been super helpful knowing I'm not the only one who's dealt with this. I'll update this thread once it's fixed in case anyone else runs into the same problem with their Vectra. Thanks again!