Refrigerators have separate systems responsible for different features. However, not all refrigerators have all systems. We will look at the most common features:

Automatic defrost
Cooling
Temperature control
Lighting
Icemaker
Ice and water dispenser
Door seals and hinges

Automatic defrost
Years ago, all refrigerators had to defrost manually. You'd turn the refrigerator off, open the door(s), and allow any frost build-up to melt. When the frost had completely melted away, you'd turn the refrigerator back on.

Today, most refrigerators are self-defrosting. Self-defrosting means what it implies--though frost continues to accumulate inside the refrigerator, it melts automatically. The self-defrosting system has three functional components:

Defrost timer
Defrost heater
Defrost thermostat

Defrost timer: 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.

Defrost heater: 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 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.

Defrost thermostat: The process ends after either a specified amount of time on the timer elapses or when the defrost thermostat near the cooling coils senses the heat near the coils has reached a specific temperature.

Cooling
It's easier to understand refrigerator cooling systems if you think of them as "removing heat from the air in the refrigerator" rather than "cooling the air in the refrigerator." All residential refrigerators work on the same principal for cooling. They all have the following components:

Compressor
Condenser
Metering Device (Capillary Tube)
Evaporator

Compressor: 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 from a low-pressure gaseous state to a high-pressure gas.

Condenser: The condenser is a series of tubes with fins attached to them, similar to a radiator. It's always somewhere on the outside of the refrigerator. It may be a large black grid mounted to the back of the refrigerator, folded up and placed under the refrigerator, coiled up and placed near the compressor or integrated in the liner of the refrigerator. If the condenser isn't a big grid on the back of the refrigerator, it will always have a cooling fan nearby to draw room air over the tubes and fins to dissipate heat from the tubes and fins. High-pressure refrigerant gas, coming from the compressor, flows through the condenser and becomes a liquid. As this occurs, the refrigerant gives off heat. The heat is conducted away from the tubes by the fins. It's important to keep the condenser clean. RepairClinic.com suggests using this handy condenser brush a couple of times a year--more often if you have pets. The condenser brush is on sale through July 18 so get yours now.

Metering Device (Capillary Tube): The metering device in most household refrigerators is a capillary tube, which is a tiny copper tube. The capillary tube is attached from the end of the condenser to the beginning of the evaporator. The capillary tube controls the pressure and flow of the refrigerant as it enters the evaporator. Once the liquid refrigerant has traveled the length of the condenser, it is forced through the capillary tube.

Evaporator: The evaporator is always located inside the refrigerator, usually inside the freezer compartment. It also resembles a radiator. When liquid refrigerant comes out of the small capillary tube, it's injected into larger tubes of the evaporator causing pressure to drop. This allows the refrigerant to expand back into a gaseous state, which absorbs heat. The gaseous refrigerant travels through the evaporator tubes, out of the refrigerator and down to the compressor to begin the circulation process again. Because the evaporator is absorbing heat, it is very cold to the touch. This coldness causes any humidity in the air to freeze on the evaporator as ice or frost. The fan inside the freezer compartment circulates the air of both the refrigerator and/or freezer to keep the temperature constant.

Temperature control
All refrigerators have a thermostat to maintain the proper temperature, and they are usually very simple devices. When the refrigerator reaches the set temperature, the thermostat interrupts the electricity flow to the compressor, which stops cooling.

Door seals and hinges
All refrigerator/freezer doors have a seal, which is a rubber-like gasket attached to the door. Usually white, almond, black, or brown, the seal's job is to keep cool air inside the refrigerator and room air out. A magnet runs through the seal to help to hold the door closed and create a tight seal. Screws hold the seal to the door to hold the door liner in and help "square" the door. Keep the door seal gasket clean to ensure it closes properly. A toothbrush and some soapy water are usually enough to tackle this job. If the gasket is brittle and cracked, you should replace it. Use our PartDetective to find the right gasket for your refrigerator.

Hinges allow the door to swing open, and some hinges also assist the door in closing. For the door to close properly, the hinges must be correctly adjusted.

For more information about refrigerators, including detailed appliance diagrams, troubleshooting information and recall information, check out RepairClinic.com's refrigerator help section.

For refrigerator accessories, including condenser brushes, light bulbs and deodorizers, check out our refrigerator accessories section.