Cruise Control: Description and Operation

DESCRIPTION
The Speed Control System consists of a Servo Assembly, Actuator Cable, Horn Relay, Steering Wheel Switches, Brake On/Off Switch, and Deactivator Switch.

The Servo Assembly is made up of a Stepper Motor with integrated electronics, eliminating the need for any electronic modules in the vehicle. The system operates independent of engine vacuum, therefore no vacuum lines are required.

The servo is mounted in the engine compartment near the Brake Booster, and is connected to the throttle linkage with an Actuator Cable.

OPERATION
When activated, the Speed Control System maintains a driver selected vehicle road speed. Using input information from the Vehicle Speed Sensor (VSS), servo motor position is varied, which in turn, moves the engine throttle linkage to speed up or slow down the vehicle.

Deactivator and Brake On/Off Switches
The Deactivator Switch is a normally closed switch and replaces the Vacuum Dump Valve as a redundant safety feature in the system. Normally when the brake pedal is depressed, voltage is applied to the Servo Amplifier from the Stop Lamps through circuit 511, which disengages the system. Under increased brake pedal efforts (5-10 lbs, engine running), the Deactivator Switch will open and remove power from the Servo Clutch (circuit 636), releasing the throttle independent of amplifier control. The Deactivator Switch is mounted to the underside of the Master Cylinder.

Vehicle Speed Sensor VSS)
The Vehicle Speed Sensor is a permanent magnet generator mounted to the transmission. Sensor output is proportional to vehicle road speed. With sensor output indicating that vehicle road speed is above 30 mph, the Speed Control System can be engaged. The speed sensor signal is then used to maintain speed while the system is operating.

Speed Control Switch Assembly
Voltage is present at the Speed Control Switch Assembly ON contact at all times through Fuse L, the Horn Relay Coil, and the Clockspring Assembly. The Switch Assembly signals the Speed Control Amplifier to turn the system on or off, to set and hold vehicle speed, and to accelerate or coast. When the ON switch is pressed, voltage is applied to the amplifier through circuit 151 (LB/BK). In "OFF" circuit 151 is grounded. With the switch held in SET/ACCEL, a 680 Ohm resistor is placed in the ground circuit. In RESUME, a 2200 Ohm resistor is placed in the circuit. In COAST a 120 Ohm resistor is used.