The evaporator area and air return channels freeze up with ice - and the refrigerator gets warm. I will replace the defrost thermostat and defrost heater, but I cannot find any reference in the parts list for a control unit, or control processor. I have spoken with Customer Support at Amana, and several authorized parts dealers and no one can tell me anything about how the defrost system is controlled or what part to order. Can any one tell me what type of defrost control system the Amana has - timer? processor board?, and where is it located in the unit? Thanks for any info you can provide. Ed

Thank you Simon - with your help I now see where the control board is listed in the parts list. Thanks for the complete answer and recommendations on the testing process - most appreciated! Ed