Up on arrival found system was flat on charge. Found King and king valve was not open all the way . Opened valves all the way , charged system with nitrogen at 400psi, hold it for 45 minutes all pressures stayed still. Released nitrogen, pulled vacuum on system. Changed system with R410A , ran out our refrigerant, got as close as I can get to preferred pressures, took delta T is 26, need return visit sometime in couple weeks to check up on the system. Unit working at this time.