If it rolls one way but not the other, that's going to be the switch. Try taking off the door panel and putting 12v into motor. It doesn't matter how you put it in there, as one way will be up and reversed will be down.
ZOMBIE THREAD! Did you have any luck fixing this? Mine might be needing replacement soon as well it wouldnt go up this morning i tried a few times and then it work but the first few times it didnt, but thankfully it went up, i didnt want to leave my window down at my office with my hunting gear in the truck