This is a convertible refrigerator or freezer and over the course of the last month has quit cooling properly in the refrigerator mode. I changed the slightly damaged door gasket and it does not help. The compressor runs as it should but only cools down to 55 degrees. There is no ice or frost on the evaporator. It stays at the same temperature (55*) in the freezer mode. Is it possible that the defrost is staying continually on even though the compressor is running on this type of unit, Or do you think its a problem with freon level.