As to the window switches, you can probably plug the connector for one of the other windows into the switch in question. Mine were intermittent on the driver's side window in my 1977 300D, and I was able to remove the switch and disassemble it, clean its internal parts, and reassemble it. Just watch out that you don't lose any of the little springs and little parts.

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Robert W. Roe
1984 300SD 167K mi