I have 1989 Merc W124 Coupe. Have just renewed the passenger door window motor thinking it would fix the 'stuck in fully up position' problem. Mechanism still does not drive. What now? Perhaps the relay? Two of the other windows are working, fourth is not.
I have discovered that the two windows that were not working are on the same fuse, which was blown! I renewed the fuse, tried the windows again, no joy, checked the fuse which had blown again. This time when I attempted to put in another new fuse it blew as I tried to put it in (burnt my thumb!).