1990 BMW 735 door sensor issue

Are the inside lights on as well? If so then the door switch is probably bad. If not then it could be a module telling lies.

Yes the lights stay on in side I have to manually switch them off or the battery will die. If it is the door switch what's the best way to find out which one an how hard is it to replace?

Ok heres the tricky part. I have a 1991 535 that did the same thing. I took out the inside light module, located in the passenger kick panel to make mine stay off. Everything still works so im not even sure what the function of the module is. But mine didn't, or doesn't, say ive got a door open. These old german cars can be a challenge. I love mine all the same. As for the door switch, ive never taken one out of that model before but the flat rate manual only pays one hour to replace the door latch so it cant be too hard. Id check the wires that bend in the drivers door hinge first if there are any. They may have broken or shorted after thousands of openings and closings