Rear passenger window doesn't work
 

We have a 96 GT convertible. The rear passenger window doesn't work - it's stuck in the down position, but all the others work fine.

I've seen that many have "fixed" their window motors by banging on the door panel by the speaker, or by slamming the door really hard, but that's for the door windows, not the rear side windows.

So far I've taken the small access panel off, unplugged the window motor and cleaned the contacts with alcohol and a toothbrush. I wasn't sure how to get the larger panels off to get better access to try the https://mustangboards.com/images/smilies/nunu.gif method.

I would appreciate suggestions - with pictures if possible - as to how to diagnose and fix this.

Thanks in advance for your help!