Evaporator could icing up. Replaced the one larger circuit board with relays but it will still not go into defrost. Have tried to advance defrost also on dispenser area keypad and no go. Did not replace smaller circuit board that looks like power center. Thermostat on evaporator was closed at low temperature. Could it be thermistor or am I missing something Else? Is there a defrost board I am not seeing? Tested heating element at the actual element and not at the board and it read OK. Any help would be appreciated. Can’t find much on this model. Thanks