If your Kenmore upright freezer is running but not freezing, even after you've checked and defrosted the coils and fan, there could be a few other potential reasons for this issue:
Compressor Issues: The compressor is the main component responsible for cooling the freezer. If it's not working properly, the freezer won't be able to reach and maintain the desired temperature. A faulty compressor may need to be repaired or replaced by a professional technician.
Refrigerant Leak: If there's a refrigerant leak, the freezer won't be able to cool effectively. A refrigerant leak requires professional repair, as it involves handling refrigerant, which should only be done by certified technicians.
Thermostat Problems: The thermostat regulates the temperature inside the freezer. If it's not functioning correctly, it may not signal the compressor to turn on or off at the right times. As a result, the freezer may not maintain the proper temperature for freezing.
Damaged Door Seal: A damaged or worn-out door seal can allow warm air from outside to enter the freezer, causing it to lose its cooling efficiency. Check the door gasket for any visible damage or gaps and replace it if necessary.
Overloading the Freezer: If the freezer is overloaded with food, it can impede proper air circulation, leading to inadequate cooling.
Condenser Coils Dirty: If the condenser coils (usually located at the back or bottom of the freezer) are covered in dust and dirt, they can't release heat effectively, which can lead to cooling issues.
Since you mentioned that the freezer was left open overnight, it's possible that it has experienced excessive stress on its cooling system, and it may take some time for it to cool properly again. However, if the issue persists after ensuring the door is properly closed and all components are functioning, it's best to contact a qualified appliance repair technician to diagnose and fix the specific problem. Attempting complex repairs without proper knowledge and experience could cause further damage to the freezer.