AQUA QRTZ DIGI RETRO FIT WALL PLT CHRME ANOR R.F.V 1/4in 65C 3.0m CAP 1407201 The thermistor works by decreasing current resistance in a manner that is inversely proportional to the temperature of the thermistor. The printed circuit board sends a current to the thermistor and can tell whether more or less heat is needed by the relative resistance in the thermistor.