Freezer stays at 15° when set to 0°

Brand:whirlpool
**Model Number:**WRS973CIDM00
Main Symptom:freezer temperature
What happens & when:stays at 15° when set at 0°

Error Code (if any):
Parts or tests already tried: freezer thermistor
Photos / video link:

Since the thermistor has been replaced, check to make sure that the evaporator fan motor is working. If the fan is running then you will then need to check and make sure that the evaporator is evenly frosted. If there is not a full even frost pattern then this would likely be a sealed system issue which would need to have a service for.

I have not yet checked for the frost level.

This was a sudden change and has stayed consistent for the past several weeks. I would think a leak would continue to degrade. Fridge always OK freezer always around 13°.

Is there a thermistor on the freezer coils as it is on the refrigerator coils?

There is a defrost bi metal on the evaporator coils but checking the frost pattern is the first step. If the unit does not have an even frost pattern the refrigerator side will stay cold as long as the evaporator is getting cold enough.

Does this look more like a defrost issue?

This does not look like a defrost issue, it would be a sealed system issue. The fact that the coils are only frosted at the bottom but nothing higher than 2 lines up would indicate this.

While checking for a possible obstructions. I noticed the compressor is marked for 240 V. This is a 120 V fridge. Could this have been a mismatch?

This unit has an inverter board from what I can see in that picture which this compressor would be correct for this model.