Open the freezer door and feel for air blowing out of the top vent area. No air, evaporator fan motor. If there is air ,close the door. Feel in the refrigerator area vent on the back wall. If no air, while feeling for air at top of the refrigerator,open the freezer door. If it flows through when the freezer door is open, your return air channel is blocked. Remove the back panel in the freezer and defrost the side channels and that should do it.