Originally Posted by S124300

I don't know anything about 190 windows, however I have stripped and regreased the W124 window motors before and they worked afterwards. Lol.
If it helps, the W124 motors have a metal casing that contains the nylon gearhead bolted on the end. The motor shaft itself has a small bearing in the end of the motor housing, but the gearhead is pretty much where everything is.
The gearwheel can't actually be removed, but by separating the gearhead and motor casings you can see inside the gearhead: Ours were full of dried, waxy, grease and that was, naturally, making everything stiff. Most of it scraped out, but I washed it through with white spirit, washing up liquid and rinsed it in clean water. After drying, the nylon gearwheel and motor shaft were repacked with molly grease and were working smoothly when it moved on several years later.