To be honest not sure how it works. Have taken off door trim, and the painted trim piece held on with 3 self tapping screws that holds the rubber seal at the top of the door in place. with the window in the down position I can look down the gap at the top of door into the door itself. There is a cable that comes up up from the electric motor ( i think ) in a black sleeve and goes over a white plastic pulley and down the back of the window guide. At the point where the black outer sleeve meets the pulley is a bit of white plastic that could be an adjuster approx 2/3cm long. This is broken in 2. I cannot work out what it does, but as it is broken it touches the glass and hence the scraping noise. Ther seems too much tension on the cable to move or dislocate the plastic away from the window. Does that make sense?