The 4 most common part(s) or condition(s) which cause the symptom Freezer not cooling are listed below starting with the most likely. Check or test each item and watch any available videos.
If the freezer does not get cold the condenser coils might be dirty. The condenser coils need cleaning about every six months to a year. If they get coated with dirt, dust and lint they will not be able to dissipate heat effectively which will affect the cooling. Some freezers have the condenser coils in the walls of the unit. These are not accessible and do not need to be cleaned.
RepairClinic Item # 1214920
If the freezer does not get cold the evaporator fan motor might have stopped working. On the back wall of the freezer, normally behind a panel which can be removed, there is a small fan. This fan draws air over the evaporator cooling coils and moves it around inside the freezer. If the freezer does not get cold, the evaporator fan motor should be checked. Often the fan motor will not run when the door is open, activate the door switch for the fan to work. If the evaporator fan motor doesn't run when the freezer is cooling and the door switch is activated, it should be replaced.
If the freezer evaporator coils ice over, the freezer does not get cold enough. Several times a day the defrost heater assembly turns on for a few minutes to melt away any frost or ice that may have accumulated on the freezer evaporator coils. If the defrost heater assembly has burned out, the frost will build up on the coils and eventually no air will be able to travel through the coils to provide cooling to the freezer. The most common cause for this condition is a problem with the defrost system.
RepairClinic Item # 1224638
If the freezer does not get cold the temperature control thermostat might be defective. The thermostat allows power to flow through to the compressor, evaporator fan and condenser fan. Try rotating the temperature control thermostat all the way from stop to stop and listen for a click. If there is a clicking sound the thermostat is probably good. If not, remove it and check it for continuity. It should have continuity when the freezer is calling for cooling.