I'm always open to thoughts on the topic. However, I'm quite certain it has a mercury filled capillary and NOT an electronic thermocouple. I don't believe one can purchase the capillary separate from the safety valve, and as long as the capillary line has not been damaged, I see no way for the mercury to leak out. Its the same principle as a mercury thermometer ... there's no thermoelectric effect taking place, it is purely mechanical. In order to possibly rule out the heater safety valve, I held a flame under the capillary bulb to mimic the heater pilot. It did not result in gas being expelled to the burner, which leads me more so in the direction of the thermostat.
