jdhiller

The right rear window is in free fall, when I run the switch I can here the motor run and it sounds like the cable is being moved but the window only moves a small amount it can be pushed down or lifted up freely. I would appreciate it if some of you that are experts (have experienced this on your car) could advise as to cause and what part to purchase before I disassemble the back seat.

Rudeney

It might just be that the plastic clip at the bottom of the glass has broken and you may be able to fashion a repair. But it could also be a bad regulator. I'd remove the side panel and investigate:

http://benzbits.com/w209/RemoveSidePanelling.pdf
http://benzbits.com/w209/RemoveSideWindowRegulator.pdf
http://benzbits.com/w209/RemoveSideWindowGlass.pdf

jdhiller

I suspect/hope that you are correct I here the cable and motor run the window just doesn't move.
I need a free day and a 8 hour window of no rain to disassemble the back seat and look at it. Is this clip which attaches the actuator and cable to the window something I can purchase at my friendly dealer or is it something I would have better luck with on eBay.
I have just had a lot of work on the roof system and it is possible that this part was not complete correctly reinstalled and worked loos over the last few weeks.

Rudeney

My advice is to remove the side panel and see what's moving and what isn't. I suspect it may be a bad regulator, but there are also a few plastic parts that can fail where the glass bolts to the regulator.