On my way back home one day, got in the car, started it and while I was backing out of the parking space, the alarm suddenly went off. And being an old S-Class Mercedes, this isn't the cute, not-to-be-rude type alarms you get on modern cars. This alarm blared with the fury of a Mongolian warlord.
Even with all that sound deadening material, and you know the type, the S-Class sound deadening, designed to mask the sound of small civil wars going on outside, from the military leaders being chauffeured - my ears were ringing in seconds.
It was cold, raining, had no tools (left the tools in what has become the most trouble-free car I own, my XJ12) and I was with friends, so all I could think of was perhaps take some fuses out. Yanked out everything that looked even remotely related, but nothing helped. With no other choice, jumped on the highway and zipped home like lightning with the alarm blaring.
After some searching on benzworld I found the location of the alarm control module and disconnected it. Apparently, it isn't the module that is causing the problem, but some sort of mico-switch in the door that is not deactivating the alarm. In any case, I couldn't be bothered with replacing micro-switches in the doors, so I just removed the alarm module altogether.
Oh and I seem to have found some sort of clamp lying loose under the carpet. No idea what its for.