Bypassing that proportional switch must be what my dad did to get our Model 80 to run after it malfunctioned. (I recall it was broken down several times; I don't know if it was expensive to fix, or if Dad just got tired of messing with it). I say this because, as I recall, it ran whenever the door was closed, without pushing any switches. In fact, I don't any of the switches worked any more except for the light switch.