Cruise Control: Locations

This electro-mechanical device contains three solenoid valves that control
vacuum in the diaphragm chamber, pulling the cable and thereby the throttle.

The individual solenoid functions are:

Vacuum valve: When energized the valve allows vacuum into the diaphragm chamber. When not energized, the valve is spring-loaded to prevent vacuum from entering the diaphragm chamber.

Vent valve: When energized, this valve prevents vacuum from bleeding off; thereby allowing speed control function. When not energized, the valve i spring-loaded open to bleed off vacuum.

Safety valve: This valve functions like the vent valve, but its vacuum bleed is larger.

Power for all the solenoids is supplied through the ON/OFF and brake switch
with one wire. Both the vacuum and vent solenoids are grounded by the engine
controller to operate speed control. The Safety valve is always grounded.