All refrigeration units, and most air conditioning systems, have the same components. Each piece must be maintained in order to keep the unit efficient.
The compressor is the most important part of the system, maintaining pressure throughout and pumping the warm refrigerant through the system to be cooled. The main cause of commercial refrigeration repair is a compressor overheating, typically due to lack of cleaning and maintenance.
The condenser cools down the refrigerant, returning it to a liquid to be pumped through the low-pressure area again to boil and collect warm air.
The evaporator keeps the refrigerator cool as the refrigerant removes the warm air through evaporation. The evaporator fan occasionally ices over, requiring servicing to keep the refrigerator or freezer at the right temperature.
The thermostat indicates to the compressor that more refrigerant needs to flow through the system to lower the temperature. If the thermostat stops functioning, your unit will also increase temperature quickly and need servicing.