Hi,

I had the same problem with the front passenger window on my 126. The clicking I heard came from the door, so I removed the trim, uncrewed the motor housing from the regulator (two star bit screws) and tried the switch. The motor was kicking round beautifully. I then unbolted the reglator frame from the iside of the door and this is the messy bit. I used about half a can of wd40 on the regulator jaws, and up inside the regulator and worked it back and for a good few times until the movement of the window against the mechanism was smooth. Upon reassembly the window now works fine.

If your window hasn't been used very often, chances are that it has just siezed up at the regulator.

Try this before spending $$$$$$$, if your motor/regualtor assembly is all one piece, and they cannot be separated then this may be difficult, but either way you may want to remove them and check.