The dimming light sign has been the following for me: YMMV. The Bosch window motors are pretty stout fellows, but they sit vertically in the 126 door and if a little "weather" gets in there, the bottom shaft bushing gets downright balky. I've seen this on cars that sat a lot outside without regular use, but could be other reasons (broken regulator jaw, regulator bent). I remove the whole window regulator and clean and lube all of it, then remove the armature from the motor and put a little 3 in 1 into the bushing "pocket". If I remember correctly, there may be a small hole on the exterior of the lower bushing pocket (a dime sized bulge on the very bottom of the motor housing) that you could sneak a little lube into without disassembling the whole thing. Then, while the inner door panel is off, "help" the window up and down a few times, while operating the switch, after lubing. A little silicone spray on the window channels and you're working (Hopefully). This has worked for me several times in the past (OK, maybe 3 times).

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)