Unplug the fridge.
Remove the wire from the J9 terminal on the main board. Measure the resistance between this wire and the neutral (orange) wire on the J7 connector (pin 9).
It should be about 22 Ohms.
If the reading is right then replace the main control board and the freezer thermistors.
If the reading is wrong then check for continuity the defrost heater and the defrost thermostat. Replace the part with open circuit.
- The part number for the main control board is
AP3950129
- The part number for the freezer thermistor is
AP3185407
- The part number for the defrost heater is
AP3183868
- The part number for the defrost thermostat is
AP3884317
Gene.