Introduction：Defrosting Thermostat Fuse ST-3

A defrost thermostat is the temperature-controlling device within the automatic defrost system of a refrigerator.  There are three components to the defrost system: a timer, a thermostat, and a heater.  When the coils within a refrigerator become too cold, the defrost timer cues the heater to click on and work to melt any excess ice buildup.  The function of the thermostat is to prompt the heater to turn off when the coils return to the correct temperature.