I had a Golf MkIV and had both front windows fail at different times. In each case the winding gear fell apart and had to be replaced.
I used a mobile car lock specialist to do the work - parts about £50 labour the same.
The winding gear sits on a metal panel behind the interior door trim (three screws on bottom and Grab-handle off to remove it). The winding motor comes off and I later had to drill out the speaker's pop-rivets.
Two rubber bungs allow access to the brackets that clamp the glass which then needs to be fully raised by hand and taped up - then the winding gear panel can be removed (5 or 6 screws). Quite simple but a bit fiddly if not used to it. Swap speaker to new panel and fit new winding gear, motor and trim panel.
Peccavi, July 2009
