There could be several reasons why a freezer is not cold, so a homeowner should troubleshoot to determine the cause. Some easy things to check include ensuring the temperature dial did not get moved and that the door is sealing properly.
If the temperature is correct and the door is sealing firmly, the condenser coils could be dirty. The coils are normally located on the bottom or rear of the unit. If they are dirty, they do not expel heat properly, and this can affect the ability of the freezer to cool. To clean the coils, the unit should be unplugged and a coil cleaning brush must be used to dislodge any dirt, dust or pet hair. A vacuum can then be used to clean up any remaining debris.
Another thing to check is the evaporator fan motor. The evaporator fan moves air over the evaporator coils and circulates it in the freezer. The fan is located in the freezer behind the back wall. If it is not working, it needs to be replaced.
If the evaporator coils are full of frost, air is not able to circulate and provide cooling even with a working fan. Frosted coils could be a result of a faulty defrost system. Other things to check include the temperature thermostat, the control board and the compressor.