CONCERN: Customer reports Refrigerator is not cooling properly. DIAGNOSTIC AND CAUSE: Found large amount of ice build-up on back wall of freezer. Tested for voltage from adaptive defrost control board to defrost heater. No voltage. Bypassed control board and tested heater circuit. Heater came on. Cause of failure found ADC main control board shorted at the output line voltage to the defrost heater. CORRECTION: Replaced ADC main control board, defrosted ice build-up around evaporator, and tested. Operation now normal.