Alan911,

You need to get a wiring diagram for your model and start tracing wires with a voltmeter or. There are wiring diagrams in the MB manuals or maybe someone here may be able to send you a copy.

I suggest you color the wires on the wiring diagram as they are marked. It makes tracing much easier.

As far as the door open/closed problem, there is probably a loose connection or broken wire in the door or door post where wires go thru.

P E H