See Figures 1, 2, 3 and 4
The cruise (speed) control system is electrically actuated and vacuum operated. The multi-function switch on the steering column incorporates a slide-switch which has three positions: ON , OFF , and RESUME . The SET button is located at the end of the three position slide switch. This system is designed to operate at speeds above approximately 35 mph (58 km/h). To operate the speed control system, consult your owner's manual.
The speed control system includes the multi-function switch on the steering column, the servo and solenoids, the speed control cable, and a vacuum reservoir. When the speed control servo receives a SET input from the switch, the vent solenoid is actuated while the vacuum solenoid is "duty-cycled". This action cause the diaphragm inside the servo to move, pulling on the speed control cable and opening the throttle. When the vehicle reaches its target speed, the vacuum solenoid is deactivated so that the diaphragm holds, and the cable is held. When the vehicle is above target speed, the vent solenoid is duty-cycled, while the vacuum solenoid is still deactivated to maintain the target speed.