An automatic self-modulation capacity compressor for an HVAC&R system is disclosed. The system includes a housing, a compressor, a motor, and a pressure sensitive control valve. The HVAC&R system further comprises an expander and a condenser. In the open position, the control valve permits a portion of the pressurized gasses from the compressor to escape, creating a partial capacity compressor within the system. Once a predetermined set point pressure differential is met, the control valve moves to the closed position, where all of the pressurized gasses within the compressor are provided to the system, thereby creating a full capacity compressor. Once the compressor is operating in full capacity, the compressor remains in full capacity mode until the demands of the system are met and the compressor shuts down. Upon restart, the compressor operates in partial capacity until the predetermined set point pressure is met once again and the compressor begins operating in full capacity.