I have read the threads and have discovered there is a box under the passenger side floor mats that can be disconnected, but someone also said that there is a fuse holder next to the main fuse panel under the hood that has two 16A fuses in it that can also be removed to disable it more easily. This may be on the 1st generation W126, but not sure. I say that because when I raise the hood, I see a red wire from fuse box with a fuse holder, but it only has one fuse in it. Ours is a 1988 model. It did this about 4 years ago when it was my car (alarming when door was opened after being locked), then it stopped for about 3 years. Unfortunately, it recently started doing it again (the car is now my mothers) and this time the door was not even locked and had not been locked. My dad opened the BACK door to put in a child car seat and the alarm started blaring. It finally stopped then the other day I went to check it out, opened the door and it started blaring again... horns, lights, etc. Horn finally stopped, but the lights kept on, I had to finally disconnect the battery and that is how it is still setting.

Can anyone provide any additional information about the way to disable it from under the hood and any pics of what needs to be disconnected appreciated. Also, if I just go the route of disconnecting the box under the passenger floor mat, do I just leave the wire loose in there? I am not sure how the connector looks, but didnt know if disconnecting it left exposed live wires under there or not.

Thanks again!