Removed rear freezer panel- 6 Phillips head screws, remove shelf brackets- and found 2 problems. The evaporator coil was touching the panel with tell tale rubbing mark on the back side, and fan bearing was worn out. Side to side movement of motor shaft showed this. Carefully bent evaporator line away from panel, replaced fan motor and blade. Old blade appeared to be out of balance which probably caused the bearing to fail in the first place.