The sunshade/rollerblind has stopped working on my 300CE. It was operating quite slowly and had difficulty extending fully. I heard a loud crunching sound when it was being retracted and then it would no longer raise. I listened to see if I could hear it working while pressing the switch to raise it but I do not hear the motor working. How do I get access to the shade mechanism and how does the device operate?

__________________
1989 300CE

I don't have access to a 124 installation but with the 126 installation it requires that you remove the rear hat shelf to get to the nuts which secure the shade mechanism in place. Once you get the mechanism out you can get to the electric motor. Most likely the toothed plastic cable which is the lifting device has broken and needs replacement. The cable makes a 90 degree turn around the motor's drive gear and when it breaks it jams in the gear box that drives it, sort of seizing the motor with a piece of that plastic cable. Replacement cable is about $35-40!