Removed back cover for evaporator coils. Using hot water and a turkey baster gradually melted ice in drain tube. This is a slow process and took several hours. Drilled out rivet and removed old evaporator heater plate. Installed new plate on evaporator coil. Insured proper position into drain opening. Riveted into place. Reinstalled cover for evaporator, checking proper connection of fan motor and defrost controls.