My 83 300SD beeps when the door is open AT ALL TIMES, whether the headlights are on OR OFF..... Normally it just goes on when the lights are on (like my 2 other 300SD's and my 300TD), but the beeping always being on makes it hard to know whether I've left my headlights on during the day (since I can't really tell).

I've tried looking around, googling, looking the service manual and I can't seem to figure out where to even look, since I don't know how to phrase this with the appropriate jargon. When I press the push-button thingy that's on the door frame (as if the door were shutting), then the beeping shuts off, whether the headlights are on or not. What is that push-button thingy called? What is the feature called when the car beeps with the lights on?

The push-button thingy only has two connectors, so I'm guessing it just closes/opens the circuit, so whatever is going wrong is elsewhere.

Also, I have TWO push-button thingies, and the 2nd one seems to not have any effect. What's that for anyway?