I have a 1996 318IC it came with the original BMW alarm system all works ok except in case the alarm is activated there is no sound at all even when the alarm is activated you can turn on the car (When the roof is down). If you open the door while the alarm is activated it will turn on the signals light. I double checked i have the alarm "buzzer" installed in my car. Any help would be grateful.

the alarm module added by the dealer is behind the glovebox. Slide it out and remove the cover and check the settings of the DIP switches. There should be a lable in the case or the cover, it may have been turned off by a previous owner.