I've had broken wires in two W124's, both Rt Front windows wouldn't lift.

I fixed my '87 300D by carefully cutting out the broken sections where insulation had crumbled and splicing new wires. This was a tedious job but using high quality US wire from the aerospace industry it has held up fine.
I just haven't the energy to tackle my '95 wagon yet.

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!