How does a dryer thermistor work?

 

A dryer thermistor is a temperature sensitive resister. It’s resistance changes as its temperature changes. The electronic control board sends out a very small electrical current to the thermistor. As the temperature increases in the dryer air flow, the resistance of the thermistor increases. The electronic control board of the dryer senses the difference between the amount of current that it sent out and compares that to the amount of current that comes back. The electronic control then uses that measurement to cycle the dryer heater relay on and off to regulate heat in the dryer drum.