Hi, there are many possibilities for the alarm false alarming when locking the vehicle & to diagnose the fault the car will need to be checked on STAR diagnostic tool to see what fault codes are stored & to see what circuit has triggered the alarm.
The most common problem by far is with an internal fault in the alarm siren - this has its own battery backup circuit & is a common failure on these models
If faulty the siren will need to be replaced & then coded on STAR after installation
Best regards, Paul
I was after a fix for this problem, and not just to be referred to a Mercedes diagnostic test. I could have taken that route without spending £2.
What would be useful would be to advise if there is a way to turn off the alarm, as at the moment I have had to remove the fuse for the central locking system in order to stop the alarm sounding. I would prefer to have central locking working and disengage alarm, is that possible within the system, either with or without removing fuses.