Upon opening the car door, an incessant beeping ensues, persisting for about ten minutes in cycles of ten beeps, with a pause in between. Only upon ensuring closure of the door does the beeping finally cease. Despite thorough checks confirming the doors are securely shut and locked, interior and exterior lights remain off, and the floor parking brake disengaged, the persistent beeping persists as soon as I open the door. Speculations about a faulty chip in the key triggering the alarm have been disproven by testing both sets of keys to no avail. It's worth noting that the car's alarm system, defunct for years, has shown no signs of activity until now(?). Any insights or recommendations would be greatly appreciated.

Thanks!

 

When I took the car to the repairman, they discovered that the old alarm system (it was not working) was causing the problem. Once they remove it, the problem disappeared.