D 100 Pickup V8-318 5.2L (1985)
Air Injection Control Valve: Description and Operation
Fig. 6 Coolant vacuum switch cold open (CVSCO)
The CVSCO,Fig. 6, provides manifold vacuum to the system after a cold start until engine coolant temperature reaches a predetermined level. After
the coolant temperature reaches this level, the switch closes and vacuum is cut-off from the air switching system. The CVSCO is mounted in the
thermostat housing.