Check from the main board white 8 pin connector from pin2 black wire to pin3 brown wire to read the resistance of the evaporator inlet thermistor and compare to the temperature table in this article to determine if the thermistor is defective. 

You can also read directly at the thermistor harness connection as shown in the diagram.

If you read 5Vdc then the thermistor is open and needs to be replaced. If you read 0Vdc then the main board is defective and needs to be replaced.