Many service technicians believe frost on a suction line or the compressor’s head itself indicates there is liquid refrigerant coming back to the compressor. This simply is not true.
All frost means is the suction line or compressor is below freezing, and the moisture in the air has reached its dew point temperature and condensed. This condensed moisture has then frozen to ice because of the temperature being below 32°F. Figure 1 shows frost coming back to an air-cooled compressor. In this photo, the evaporators had over 9° of superheat and the compressor has over 25° of total superheat. The amperage draw is also normal when compared to nameplate amperage.