True refrigerator help?

I have a model GDM-26. It's was blowing really cold, 30 degrees, then warm, 50 degrees, alternating between the two. Now it's not blowing cold at all and the coils on top do not get cool/cold. Both upper and lower fans are working, the compressor is running smooth no clicking on or off and the condenser on the bottom is totally clean, also the thermostat seems to work, it turns the compressor off when you switch it to zero. It was manufactured in 1999. Any help would be appreciated,