Glossary “vacuum control valve” Definition:
A ported vacuum switch. Controls vacuum to other emission devices during engine warm-up. The 2-port types simply open when engine coolant reaches their pre-determined calibration temperatures. The 4-port types open likewise, since they are nothing more than two, 2-port types in one housing. The 3-port types switch the vacuum source to the center port from the top or the bottom ports. Most VCV’s respond to a sensing bulb immersed in engine coolant by utilizing a wax pellet principle.