Vacuum Control Switches
WARNING: This page is about a different car, the 1995 Ford Ranger. However, it is still accessible from the selected car via links, so may be relevant.
Temperature-operated vacuum switches have 2 or more ports. They utilize wax pellet or bimetallic material to either open or close the vacuum ports in conjunction with engine temperature.
Switches are normally mounted in some part of cooling system so the base is immersed in coolant. Switches may be normally open or normally closed. One version includes an electrical vacuum switch.