My rear window is to the point where it will barely raise itself at all. When I press the switch, the interior lights dim while the window is trying to move. Whether the engine is running or not seems to make little difference, and I have two batteries (in parallel) both in good shape. The starter cranks like crazy, so I don't think I'm hurting for battery power. Any suggestions where to start looking first? I could swear I replaced the little motor only like 5 years ago or so.