Same problem here. When we picked up the coach it worked, a few days later it quit. I couldn't get the screen off to manually turn the blades, so it's on my list of things to ask the dealer to fix. New 2014 Greyhawk 31FS. We had one of these in our old Minnie Winnie. The big knob is only to open or close the vent if the a motor quits, it has nothing to do with the fan itself.