Removed the freezer shelves and back panel, evaporator coils were frozen with ice. Defrosted coil and removed defrost heater connectors, measured no continuity in the heater and ordered a replacement. Also discovered the aluminum retention strap was broken and the heater had slipped down in it's position, ordered and replacement strap. Re-installed new heater and strap per the video instructions, repair complete. Most difficult steps were drilling out the drain pan rivet and re-threading the heater through the evaporator coils.