To troubleshoot a refrigerator that isn't cooling, check the thermostat to ensure it is on the proper setting, test the power supply, and examine the vents inside the freezer and refrigerator. Move any items blocking the vents. Clean the coils and evaporator fan, and check the operation of the compressor, condenser fan and evaporator fan. Replace the evaporator fan if the compressor isn't running. Replace the condenser fan if it doesn't turn on or if the compressor is hot.
If the compressor is running, unplug the refrigerator, and remove the interior cover on the back of the refrigerator. Frozen coils often indicate a problem with a defrost component. Allow the refrigerator to remain unplugged for 24 to 48 hours, and test the refrigerator.
If the refrigerator works after thawing it, replace the defrost timer, defrost thermostat or defrost heater. Noisy operation indicates the need to replace either the evaporator or condenser fan. Often, dirt and debris cause the fan to operate poorly. Clean the fan if it appears dirty, and test the refrigerator again before replacing the fan.
Low coolant levels are indicated when the refrigerator is operating properly but slowly becomes warmer over a period of time. Have a professional check the Freon levels in the refrigerator, and recharge the refrigerator to resolve the issue.