Hi all, been looking through some of the posts regarding the alarm systems on the Class 1 W126 (specifically, 1985 CA edition diesel). Mine will randomly go off when the car is locked. I can't seem to find a timing and/or trigger. I've had it go off in the middle of the night and I've had it go off about 15 minutes after locking it.



To the best of my knowledge, the only thing to be modified is my disconnecting the ground connection when I installed my Blaupunkt radio. I tucked the alarm ground/trigger wire up and away so as to not find any ground points.



Where should I start looking for issues? I've read a few threads about micro switches in the door locks, is that a common start point? Thanks.

In the drivers side door, check the connector. On the inside of the door, in the middle is a round rubber plug, remove it and you will find a connector with several wires. The connector might be brittle or kaput and shortening out the wires.

This was the case with my 1990 300SE, not sure if the gen 1 has the same set up. I had the problem after heavy rain for several days.

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1979 Black on Black, 300CD (sold), 1990 Black 300SE, Silver 1989 Volvo 780, 1988 300CE (vanished by the hands of a girlfriend), 1992 300CE (Rescue).

Here is a picture of the location of the plug.

Attached Thumbnails

 

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1979 Black on Black, 300CD (sold), 1990 Black 300SE, Silver 1989 Volvo 780, 1988 300CE (vanished by the hands of a girlfriend), 1992 300CE (Rescue).

I'll give that a look.

Interesting you mention rain because I believe the alarm is more likely to go off after a car wash (it's doesn't rain much in San Diego).