Your problem was in the switch. I've cleaned all switches, and
switched switches, to check that they all work. I've taken apart the
female connectors as well, and even tried changing pin connections
temporarily, since the colors on the wires don't exactly match the
factory repair CD info. But I'm back to this one window and the
instrument lights short. I think you're right--someone has fiddled
with the radio or A/C and crossed a wire somewhere.
No, my mechanic didn't do this. He is amazing. German-trained master
mechanic and master electrician. He learned about brakes in the brake
factory, engines in the engine factory, etc. But I use him only for
the basics. This is the kind of fiddling problem that takes hours to
track down, and it's not a great inconvenience to me that the left
rear window won't open.
I bought this car a couple of months ago from a very nice lady who
looked after it extremely well, but had some Bercedes-Mends mechanic
repair it. You can tell when you see little things broken (like the
tabs on the plastic frames around the rear window switches) from not
knowing how they come out. I can just picture him saying, after prying
something out with a screwdriver, "Ah so that's how they did it!"