[cessnadriver]

Hello all. My '65 C337 pilot's side heater vent is not working properly. When I turn the heater knob to the 12 o'clock position the knob turns, all by itself, to FULL (While in the air). I temporarily fix it by grinding the knob around the circumference and added a screw. I've looked at the parts manual and checked my "parts bird" but can't see how the cable and valve assembly works? I'm thinking that the return spring, mounted around the shaft of the valve, is broken? I haven't removed the battery and the box to get a real good look at the valve. Just looked up through the left side cowl flap. Any body got a clue??
Thanks, BILLS
PS: With the battery on that side I do see a lot of battery acid corrosion in and around the heater valve!!