When we recently bought this 1993 B190, the door courtesy lights would not go out. Today I finally got around to de-bugging the problem. I started at the back door switch, and it was okay. Next I removed the side door switch, and noticed it did not protrude as far as the rear door switch, which was basically identical. The switch housing had slid into the nut shaft almost 1/2". Sorry, should have taken a picture. Anyway a few light taps on a deep socket placed on the nut face and the housing was back in correct position. I used some green loctite, which seeps in and hopefully locks the two pieces together. Reinstalled the side door switch and now the courtesy lights go off. I had removed the bulbs from both door courtesy lights to prevent running the battery down.
Now, our 1991 B190 did not have the door lights, just the overhead lights. So, at night, all you had to do was rotate the headlight switch to activate the overhead lights to read in the swivel passenger seat. Now, the door courtesy lights are also on. Bummer. May remove those two bulbs anyway, or add a house light above swivel seat. Anyone else run into this situation and come up with a solution?