Well here is another problem on my 1990 300SL.
The LED lights (Arm RED and Dis-Arm GREEN) in my door handles and trunk no longer function. The Alarm will not work as it did before. I have changed the batteries on both of my hand factory keyless units. I tried to re program the keys (when batteries go bad) This has happened over this past winter, it all worked flawlessly before. I looked for blown fuses, none that I could find. I know there is some sort of controls under the passenger side floor mat. If I leave all doors unlocked, I can drive the car. If I should lock the car, upon reentry and start the car, If I move the car a few feet the lights and horn flash, the engine still runs. The only way to stop the alarm is to take the key out of the ignition and put in drivers door (Outside) and turn key clockwise to stop it. Does anyone know what this problem is? Module etc.? Can I just unplug this from the under the passengers floor mat.? then what? I would like this to work as before as a fully restored alarm / warning system.

Thanks Guys AGAIN!!