Vacuum Advance Control Solenoid: Description and Operation

Fig 50 Vacuum Solenoid Valve:

This electrically-operated solenoid valve, Fig. 50, used on models with automatic transmission and air conditioning. The solenoid is energized when the A/C compressor clutch engages and switches the vacuum signal to the advance unit from manifold vacuum to carburetor ported vacuum.
- Ports 1 and 2 of the valve are connected when the solenoid is energized.
- Ports 3 and 4 of the valve are connected when the solenoid is deenergized and switches from carburetor ported vacuum to manifold vacuum.