The defrost thermostat is useful in a refrigerator because it regulates the freezer's temperature rise during the defrost cycle. A malfunctioning defrost thermostat creates temperature imbalance in the freezer which may hinder the normal operation of a refrigerator.
When the temperature in the freezer compartment reaches a preset level during the defrost cycle, the defrost thermostat automatically opens to disconnect the electric power supply to the defroster. A faulty defrost thermostat can either hinder the turning on of the defroster heating elements or keep the elements on for excessively long. This can result in food spoilage or even a fire.