Almost sounds like a bad contact or loose wire deal here!The only thing you could do is try to trouble shoot the actual switch for continuity when its on and bang it around a little. Maybe trying something with an OHM meter and the switch connection. I'm not much of an electrical wizard but thats what I would try first. When people ask me if I know what a "Wheatstone bridge" is.....I always say its some bridge in NY! Sorry I could not be of more help!