74 duster brake light switch

its not the parking brake lever switch that was my first thought it has no effect when unplugged the switch on the proportion valve is the culprit, I really don't see the master being at fault either as the brakes work just fine, my thought is that the contaminated brake fluid has jammed the switch, I was wondering if it was like a reverse lamp switch that has a dent ball on it that may be jammed?, I will try to remove it later and see if it can be cleaned