Genuine Fujitsu 9810366009 Outdoor Compressor is the sealed rotary compressor in the outdoor unit, the part that pumps refrigerant around the system and makes heating and cooling happen at all. When it stops or struggles nothing else can make up for it, and the unit reports compressor faults instead of delivering warm or cool air. The genuine compressor is the two-cylinder rotary unit with the 6-pole brushless DC motor that this outdoor inverter drives.