Mine has been doing this, I thought that I was going to need a new sounder or battery in the sounder, but my altenator has just packed up so it may be that the battery was running low, which can cause the alarm to go off. I have got round it for the time being by unlocking the car and then open the rear passenger door, reach round and push the button down on the drivers door and then shutting the rear door. The alarm is not set but the car is locked. Check your car battery power first before buying a new sounder.
Angie
April 2009