Idle Up Control Valve: Description and Operation

Fig. 20 Idle Control System Wiring And Vacuum Hose Diagram:

The A/C Idle Boost Solenoid Valve, mounted on the right side of the firewall, is used by the PGM-Carb unit to control idle speed. When the compressor is activated, the PGM-Carb unit sends current to the A/C Idle Boost Solenoid Valve. As the valve opens, manifold vacuum is passed through to the diaphragm chamber of the idle boost controller. The idle controllers diaphragm rod is retracted to open the throttle valve a certain amount.
The amount of this throttle valve opening is adjusted with the idle control screw on the idle controller to maintain the original idle speed. When the compressor is off, the A/C Idle Boost Solenoid Valve is deactivated to close the vacuum passage and the vacuum stored in the controller is released through the filter on the solenoid valve.