Cruise Control: Description and Operation

Fig. 1 Electronic cruise control components:

The Electronic Cruise Command control system regulates cruising speed by the use of a servo unit which uses engine intake manifold vacuum to regulate throttle position. The servo unit is controlled by an electronic regulator which receives input voltage from a speed sensor. The Electronic Cruise Command control system consists of the following components.

CONTROL SWITCH
The control switch is an integral part of the turn signal lever and activates the system.

REGULATOR
The regulator is an electronic device that senses speed through an electrical signal from the speedometer cable speed sensor. The regulator has a built in circuit to prevent operation below 30 mph.

Fig. 2 Servo Assembly:

RELEASE SYSTEM
This system de-energizes the cruise command control system in two ways, electrically and mechanically. Both release systems are activated by depressing the brake pedal. The mechanical vacuum dump valve admits atmospheric pressure into the servo. The electronic regulator deactivates the servo by closing the vacuum charge valve and opening the servo vent valve. This release action is caused by current flow through the brake lamps to the regulator assembly which signals the solenoid controlled valves in the servo.

SERVO
Controlled by the electronic regulator, the servo uses manifold vacuum for diaphragm motion. On all models except 1982 - 86 6 cylinder engines, a bead link chain connects the servo cable to throttle linkage. On 1982 - 86 6 cylinder engines, a cable with an integral "lost motion link" at the throttle end of the cable connects the servo to the throttle linkage.

Fig. 1 Electronic cruise control components:

SPEED SENSOR
The speed sensor is a tach-generator unit that is mounted between the upper and lower speedometer cables. This sensor converts speedometer cable revolutions into input voltage for the regulator.