anti theft alarm problem with 1987 300SDL
 

I have a weired anti theft probelm.
The alarm goes on from time to time. It is unpredictable an dI don't know the reason why. It occurs more and more. I found out that I can cancel the alarm by locking and unlocking the trunk but other than that it is a mystery to me.
Does anyone know how the anti theft works and what might be wrong.
Any idea how to solve the issue? Thanks
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Each door has a trigger as does the hood and trunk lid. See if any of the pin switches is/looks loose or misaligned. Some cars have a motion/anti-tow sensor in the trunk.

The common thing to do when the alarm gets flaky is to disconnect either of the connectors at the controller. The controller is behind the firewall panel in the passenger footwell.

Sixto

anti theft
 

Thanks
Where exactly is the controller in the passenger footwell?
And what is it doing?
I also don't understand how the systems really works. I guess it is armed by the key and the alarm goes on if someone tries to open the doors without disarming with the key.
So what happens is: I can arm the system with the key but by turning the key when I open the door the alarm is not set off, and when I move the door the alarm goes on?
The arlarm system thinks that someone is breaking in?
This would mean that the triggers at doors and trunk work well?

Remove the front passenger carpet, remove the one or two nuts that take a 10mm socket holding the forward plastic panel to the firewall, locate the long box with Becker markings.

The door and trunk key lock mechanisms have a switch set that arms and disarms the alarm. Sometimes the switches wear to the point that they'll arm but not disarm or vice versa. Check the wire diagram for central locking or anti-theft at mb.braingears.com for help with diagnosis.

Sixto

When unlocking make sure you turn the key all the way to stop.