4165. When charging refrigerant into the system as a vapor with the compressor running using the service gauge manifold set illustrated in figure «C» of the illustration, what is the correct position of each of the hand valves

During vapor charging with the compressor running, valve 18 (low-side) must be open, valve 21 (high-side) closed, valve 22 (REF) open, and valve 27 (unused port) closed to ensure refrigerant flows only into the low-pressure suction line.