[leftybass209]

I think you pretty much narrowed it down. If the only variable to the equation is heat, then the switch could be the case. how does your wiring look, and does it feel brittle? Are there any splices or jumpers along the wiring? You can first check the switch by cleaning the contacts with a brass wire brush if they are visibly corroded. That's not to say something isn't wrong inside of it though.