A quick fix is to just disconnect the horn, which is located in the boot on the left hand side, behind the pannel. It sounds like the switch in the door lock has broken. Inside the lock is two switches, one for turning the key clockwise and one for counter-clockwise (double locking and arming, and the other disarming). These can easily be replaced. You can do a test on the alarm system by opening the bonnet, with all doors closed, and press the plunger switch 8 times. The horn will sound, and the car will go into test mode. Then, open each door in turn. one horn blast indicates it's working, silence indicates a fault. Test the locks by locking and unlocking the car, and listening for the horn.
Hope this helps
Rob
Rob, August 2006
