Refrigerator not cooling, freezer thawing but cold.

I removed the back lower panel within the freezer compartment. The cooling fan which draws cold air from the evaporator unit was functioning fine. I then unplugged the unit.
The evaporator unit was frozen in a block of ice. I removed all food contents from both the freezer and the refrigerator, moving them to a back-up refrigerator. I then allowed the radiator to thaw completely overnight. Upon restarting the unit it became cold within an hour thus I new the compressor was fine. I surmised it must be a defrost issue. I then unconnected the defrost heater and thermostat assembly. The device was easy to remove. I then routed the wire of the new assembly on the side of the evaporator unit and clipped the thermostat back onto the cooper feed, plugged the unit into the connection. Next I turned my attention to replacing the adaptive defrost timer. In the top of the refrigerator compartment, I removed the plastic shroud, by sliding back and pushing the plastic clips in. I took out 4 screws holding the unit to the ceiling of the refrigerator. Slowly lowering this, I could see the adaptive defrost timer in the right rear corner. I simply unplugged the unit and replaced with a new unit. I replaced both items although I am unsure which was not working. Refrigerator is working fine now.