Cruise Control: Description and Operation

CIRCUIT OPERATION

The Cruise Control system maintains a set vehicle speed when engaged. The system cannot be engaged below 25 mph. Power to the system is provided through the IGN/GAUGES Fuse and the PNK/BLK (139) wire with the Ignition Switch in RUN or START.

The Cruise Control Module receives inputs from the Cruise Control Switch, the Digital Ratio Adapter Controller (DRAC), the Brake Switch (also the Clutch Switch with manual transmission), and the Servo Position Sensor in the Cruise Control Servo.

The Module opens and closes the Servo Vacuum Valve and Servo Vent Valve to maintain the set speed. If the vehicle speed drops, the Vacuum Valve is energized allowing vacuum from the Vacuum Reservoir to be applied to the Servo Diaphragm. This pulls the Diaphragm in, which pulls the throttle open. If the vehicle speed increases, the Vent Valve is energized to vent vacuum. This releases the Diaphragm, which closes the throttle. The Cruise Control Module constantly cycles these valves open and closed to maintain vehicle speed to within mph of set speed.

The Cruise Control Module monitors the vehicle speed input from the DRAC and the input from the Servo Position Sensor to determine the cycling of the Vacuum and Vent Valves.

The Cruise Control Switch (part of the Multi-Function Switch) turns the system ON and OFF. The speed is set by momentarily pressing the SET switch in the end of the Multi-Function Switch. Once the speed has been set, the vehicle can be slowed by pressing and holding the SET switch. This disengages the system allowing the vehicle to slow down. When the desired speed is reached, releasing the SET switch engages the system and the new speed is maintained.

Vehicle speed can be increased the same way by pushing and holding the RESUME/ACCEL Switch. Depressing the Brake Pedal or the Clutch Pedal (manual transmission) opens the Stoplamp or Clutch Switch stopping the signal to the Cruise Control Module. This disengages the system. A Brake Vacuum Release Valve is also mounted on the brake pedal arm. When the brake pedal is depressed, the vacuum in the Cruise Control Servo is vented through this valve.

After disengaging the system through the Brake or Clutch Switch, the system can be re-engaged at the previously set speed by momentarily pressing the RESUME/ACCEL Switch. This opens the throttle until the set speed is reached.