The temp selector switch on dryer has no effect?

My Kitchenaid elect. dryer, model YKEYE777BWI, dries at the hottest setting all the time. The switch has 4 positions, but regardless of how it is set, it stays on hot. There is a thermostat, called an internal bias thermostat mounted on the blower housing. This seems like the culprit, but I'm guessing, because I don't know EXACTLY how this portion of the circuit works. Any help is appreciated.