Cruise Control: Description and Operation

OPERATION
The Speed Control Amplifier controls vacuum to the Speed Control Servo Motor through the Modulating Valve. The Servo Motor moves the throttle through the Actuator cable.

To operate the Speed Control System, the engine must be running and vehicle speed must be greater than 30 mph. The System is turned on by pressing the Speed Control Switch "ON".

Set
Pressing and releasing "SET/ACCEL" or "COAST" sends a command to the speed control amplifier. This command makes the vehicle's current speed the set speed. The Programmable Speedometer/Odometer Module (PSOM), (located in the Instrument Cluster) sends a speed signal to the input of the speed control amplifier through the 679 (GY/BK) wire. This signal tells the amplifier to increase or decrease the vacuum at the servo motor to keep the vehicle at the set speed.

Acceleration
Pressing and holding "SET/ACCEL" increases the vehicle's speed as long as "SET/ACCEL" is depressed. Releasing "SET/ACCEL" gives the system a new set speed to maintain. Vehicle speed may also be increased by depressing the accelerator until the higher speed is reached, then depressing and releasing "SET/ACCEL".

Coast
Press and holding "COAST" decreases the vehicle's speed as long as "COAST" is depressed. Releasing "COAST" gives the system a new set speed to maintain.

Off
Pressing "OFF" turns off the system (grounds LB/BK wire). The system is also turned off when the brake pedal is depressed or the ignition switch is turned to "OFF". The vacuum dump valve also operates when the brake pedal is depressed. This is a backup device that releases the servo. In vehicles with manual transmission, the clutch switch opens when the clutch switch opens when the clutch pedal is depressed and turns off the system.

Resume
When the system has been deactivated by depressing the brake or clutch pedal, the last set speed may be resumed by pressing "RESUME". This feature will not work if "OFF" has been depressed or with vehicle speed below 30 mph.