Ahmed,
Newly done this week was an overhaul of the door checkers and they now work a treat! better than a quick fix with grease.
Remove the door cards then the speakers, tap out the pin holding the strap to the inner wing and unscrew the two nuts holding the unit to the door then remove it through the speaker aperature. With the unit held in a vise, prise back the four tabs and remove the back plate to reveal two heavy springs, ease them out with a screw driver. On the end of the spring is a white nylon guide and within the guide is a small metal roller just over 6mm dia, which pinches the strap, if like mine they have flats on them this is what causes the rough action and noise. I replaced them with cutting them from a chrome vanadium screw driver (the shaft) which was the same dia.
Once degreased, cleaned and reassembled, I soaked the whole unit with Teflon grease, a can of Castrol Motor bike chain wax is ideal, my doors now have a quality sound...smooth and quiet.
John
