What effect does the PAX OFF position have on the passenger hot/cold valves?

The PAX OFF position is designed to optimize cabin conditions when the aircraft is not in passenger use. When this position is selected, it effectively closes the passenger hot/cold valves. This action prevents airflow to the cabin, ensuring that the temperature and airflow can be better controlled or minimized when the aircraft is not occupied by passengers. By closing these valves, the system helps to conserve energy and maintain a more stable environment within the aircraft during these times.

The other options do not align with the function of the PAX OFF position. Opening all valves would contradict the purpose of shutting down the system when not in use. Operating the valves independently is not part of the PAX OFF function, as it focuses on sealing off passenger comfort controls. Finally, signaling the crew for action does not relate to the mechanical function of the hot/cold valves but might pertain to operational procedures outside the context of cabin temperature control.