Mine runs very intermittently. I've got my 501 is a very well ventilated area, so I suspet that mine doesn't get hot enough to run the fan very often. If you've got yours in a well ventilated area and the room that it's in doesn't get very warm, then I would suspect that your fan wouldn't run very often. Of course, the other possibility is that you've got a fan that is doa. If the top of your 501 gets hot, I'd call dish.