Here's what the gas valve looks like. It has an off/pilot/on position, and the white dial is the temperature selector. The Sensing bulb is supposed to act as an analog thermostat, telling the heater to turn the flame on or off.
No ball valve on this one, although that might be an idea, rather than having full size flame, one could dial it down on the gas output side to reduce flame size, and thus, heat. If I don't get t he sensing bulb sorted out I might do that.
You can see to the left of the temperature dial, the copper wire leading to the sensing bulb. I'd be curious to see what it looks like inside the gas valve, maybe it's loose inside and not giving a proper signal to the valve.
