Neither the council nor any of its members shall dictate the appointment of any person to office or employment by the manager, or in any manner interfere with the manager or prevent the manager from exercising judgment in the appointment of officers and employees in the administrative service; but this shall not be construed to prohibit the council from passing ordinances for establishing a merit system governing city employment. Except for the purpose of inquiry, the council and its members shall deal with and control the administrative service solely through the manager, and neither the council nor any of its members shall give orders to any subordinate of the manager, either publicly or privately.