Window regulator or motor not working?
 

Car is 92 300E.

Driver's side window will always go down but lately it does not want to go back up. Had this problem for a year or so but it's getting worse. Tested switch and it's fine.

Since the window will go down reliably but not up reliably does that mean the problem is with the regulator and not the motor?

Can the regulator be reconditioned to function normally or will I have to replace it?

Never hear any machine gun noise like something slipping on gears.

either way, chances are excellent you'll need to remove the door panel to fix it. If you do, check the regulator for binding. I had this problem recently on my SD. I took the regulator and motor out together. Regulator looked fine. I then removed and disassembled the motor (it only took about 3 minutes). The lower bushing was rusty and nasty. I brushed it out, lubed it with lightweight oil and reassembled. Now, it works better now than it did 9 years ago. :)

That may be my problem. I had the interior panel off a couple of months ago to install a new door check strap but the window was working pretty regularly then. I though about taking the motor and regulator out then but it looked like there was a lot going on in there and I did not want to deal with it. Looks like now I'll have to.

It is the regulator. An easy way to make sure is to turn the engine off key on with the interior lights on. Hit the window switch, if the lights dim than it is not the motor. The lights dim because the motor is trying to work but the window won't move because the regulator is jammed