When I connect the upper passenger door switch the wiring sparks and starts to melt, I also have no dome light with the doors open (light works when switched on), or headlight buzzer. The sealtbelt buzzer and light work, I tried replacing the seatbelt relay under the dash but it didnt fix anything. Any ideas?

You'll probably find a bare wire inside that accordion boot which houses the wires going from the body to the door. That is the most vulnerable place in the door wiring route.

Replacing that boot is satisfying until you realize the right side is just waiting for your attention.

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84 300SD
85 380SE
83 528e
95 318ic