Looking for some help here. Car is 1990 W126 300SE. The problem is the driver's door switch functions do not work with the door open - only with the key on, or with the passenger door open. In other words, when I open the driver's door I get no interior lights, seat adjustment switches do not operate, and worst of all, the buzzer indicating lights on or key in ignition also does not sound. I have replaced the door switch/button, with one known to be good. I suspect a relay, but don't know which direction to head next. Everything on passenger side door works fine, in fact all functions on drivers door with passenger door open.

I hope someone can help point me in the right direction.

Thanks, Jon

You should look for the buzzer relay at driver side under panel right next to cruise control box. replace it or you can repair the damaged circuit bord if it is not damaged so bad

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MB STARS Master Guild Technician,17 years MB tech
14 years independent shop owner