Avanti brand, shp1700 won't cool. Fridge compartment only, no freezer. Back is completely enclosed w/o easy access. After exposing back with great effort, I see a control board, large span of black coils, but can't find a compressor, even though the label specifies 20 ounces of r134a. If this is a non compressor unit, why is refrigerant listed? Avanti cs completely clueless, except it is out of warranty. Any advise as to what I have here before I toss it as a lost cause?