If your freezer is not blowing cold air despite checking the seals, cleaning the coils, and replacing the evaporator thermostat, there could be a few other potential reasons for this issue. Here are some possibilities to consider:
Faulty Condenser Fan: The condenser fan is responsible for dissipating heat from the condenser coils. If the fan is not functioning properly, it can lead to poor cooling in the freezer. Check if the condenser fan is spinning freely and replace it if necessary.
Defective Evaporator Fan: The evaporator fan circulates cold air from the evaporator coils throughout the freezer compartment. If this fan is not working, the freezer won't cool properly. Inspect the evaporator fan for any obstructions or damage and replace it if needed.
Compressor Issues: The compressor is the heart of the refrigeration system, and if it is malfunctioning or not working at all, the freezer won't cool. Listen for any unusual noises coming from the compressor or feel for vibrations to determine if it's running. If the compressor is faulty, you may need to call a professional technician to diagnose and fix the problem.
Low Refrigerant Level: If there's a refrigerant leak in the system, it can result in low refrigerant levels, which can lead to inadequate cooling. Recharging the refrigerant and fixing the leak would be necessary to resolve this issue. Handling refrigerant requires expertise, so it's best to leave this task to a qualified technician.
Thermostat Calibration: Even if you've replaced the evaporator thermostat, there's a chance it may not be calibrated correctly or is incompatible with your freezer model. Double-check the thermostat's settings and ensure it's functioning properly.
Control Board Problems: Many modern freezers have electronic control boards that regulate various functions. A malfunctioning control board can cause cooling problems. If you suspect an issue with the control board, it's best to have it inspected and replaced by a professional.
Since you have already performed some troubleshooting steps and replaced the evaporator thermostat, and the issue persists, it might be time to contact a qualified appliance repair technician. They have the expertise and tools to diagnose complex issues and perform repairs on your freezer.