Window question

Greetings all !

I have a 1980 MB 300D that has a problem and thought I could take advantage of your collective wisdom. The problem is that the front passenger window rolls down nicely but only goes up 3/4 of the way without "help" . How can I tell if this is a window motor problem? or a window regulator problem?
Thank you for any/all suggestions !

[mike690003]

It seems to me that you might have a sticking window regulator. Take the door panel off and grease or WD-40 the regulator. That should do the trick. Those window motors never die,the regulators tend to stick quite often,especially in older MB's.