I'd try squirting a shot of WD-40 into the slot behind the offending knob...if you can get the liquid into the switch, it'll likely make the switch work for a while. I somehow got an extra year or so out of a seat switch that way.
"If everything seems under control, you're simply not going fast enough" --Mario Andretti
1995 E500 street car
1986 Porsche 944 Turbo S track car