A fridge compressor works by raising the pressure of the refrigerant by constricting the vapor, then pushing it through coils on the outside of the unit. The compressor is one of five basic parts to a refrigerator. The other four are the refrigerant fluid, condenser and evaporator coils and the expansion device.
If a person notices that his or her refrigerator is not cooling as it should, the problem may lie with the compressor on the unit. If the compressor is not working, the refrigerant will not be compressed to a high enough temperature to cool the refrigerator. The fridge's compressor is an integral part of how efficiently a refrigerator works.
As the compressor constricts the refrigerant vapor, the temperature of the vapor rises. When this heated vapor gets pushed through the coils on the outside of the fridge, called the condenser coils, the vapor condenses into a liquid as the coils remove the heat from the vapor. This liquid is then pushed through the expansion device, which lowers the pressure. It then goes through more coils on the inside of the fridge. These are known as the evaporator coils. As the liquid moves through the evaporator coils, it absorbs the heat inside the refrigerator which, in turn, cools the air inside the fridge. As it goes through the evaporator coils, the liquid once again turns into a gas and eventually makes its way back to the compressor.