Cruise Control: Description and 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.

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 (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.

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.

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.

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 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 transaxle, the Clutch Switch opens when the Clutch Switch opens when the clutch pedal is depressed and turns off the System.

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 car speed below 30 mph.