Xsara alarm malfunction

Hey, that sounds familiar. I had a similar issue with my old Opel Astra, though it wasn't exactly the same year. The problem was the alarm system was coded to activate optical locking, which is, the indicators light up upon locking. Have you checked if your indicators are working when you lock/unlock the car?

Thanks for the quick reply! By optical locking, do you mean the hazard lights flashing when locking? I'll double-check, but could that really disable the whole alarm system? And how did you fix it on your Astra?

Yes, hazard lights indicating the lock/unlock. On my Astra, the alarm system was completely dead because of that misconfiguration. You should probably check the car's computer. If you don't have the equipment for it, best to go to a workshop, they should be able to read and reset it.

I went to a mechanic, and it turned out the alarm system was indeed coded incorrectly regarding the optical locking. They recoded it, and everything is working fine now. Total cost was 45€. Thanks a lot for your help!