my son has an '84 190e with a sunroof problem. i'm not too shy about tearing things apart so i went inot the trucnk and had a look see about the problem. if you pushed it back and pulled it forward ithe would work with the motor sometimes. the crank in the trunk didn't do much either.
i pulled the motor off of the cable and out of the truck. there is a very large metal gear in the center of the motor that engages the cable which goes to the sunroof. our gear was worn so badly, there was a grove worn right around the center, that there was no way it would work even with help.
anyway to the dealer i go and try to order a gear. no way jose. no gears available. you have to buy the entire motor to fix the problem. not cheap; used 135 and new 275. i htink yo could probably have a new gear made at a machine shop for less. but anyway we will get the new motor and install it. that should fix the problem. \\i will check to make sure the gold clip is attached properly to the sunroof itself.
i have talked to the dealer and they say that the key here is to keep the roof glides lubricated and the cable greased. this should minimize the weat on the gears.