Wonder How It Works ?

The timer is like a clock. It continually advances, 24 hours a day. Every 6 to 8 hours, the timer turns off the cooling system of the refrigerator and turns on the defrost heater.The process ends after either the amount of time specified on the timer or when the defrost thermostat near the cooling coils senses that the heat near the coils has reached a specific temperature.

The compressor is the motor (or engine) of the cooling system. In built-in refrigerators the compressor is located on top of the refrigerator behind a grill or grate. In all other units it's normally at the bottom of the refrigerator in the back. It's almost always black and about the size of a football. If the refrigerator is self-defrosting, the compressor may be behind a thin panel. The compressor runs whenever the refrigerator thermostat calls for cooling (and the defrost timer is not in a defrost cycle, for self-defrosting units). It is normally very quiet. When running, it is compressing a refrigerant that is in a low-pressure gaseous state to a high-pressure gas.

The defrost heater is similar to the burners on an electric stove. It's located just beneath the cooling coils, which are concealed behind a panel in the freezer compartment. The heater gets hot. And, because it's close to the cooling coils, any ice or frost build-up melts.

As the frost and ice melt, the resulting water drips into a trough. The trough is connected to a tube that drains the water into a shallow pan at the bottom of the refrigerator. The water is then evaporated by a fan that blows warm air from the compressor motor over the pan and out the front of the refrigerator.