My drivers side rear window stopped working the other day. It used to stop working and I'd just give the inside of the door panel a whack, and it'd start working again. Now, I whack it and no luck. I've pulled the door panel to look at the mechanism amd nothing obvious like a loose connection or anything. Any way to check if it's the motor only... or something in the gears?

Seems like it would be easier to replace only the motor (no rivets to remove) but obviously I don't want to do that, if that's not the problem.

Any help?