Excuse my stupidity...............thermistor=thermal REsistor, not transistor........I should learn when to shut up...........
and, to modify my past idiotic statement, I may NOT have seen the gauge drop after it went up then lost water. In short, I lied. Getting quite messed up in that hard drive of a brain after 45+ years. Was thinking it out, the sensor will not read air temp but will after water has steamed up passages. They WILL actually read air temp, but the response change is so slow that you may as well accept they don't. Fluid conducts heat to the sensor so fast the result is quick, but air heats up slowly unless the temp dragged up really quick by super hot steam around it. In that case the air would read on sensor too since it is very hot also.