Cruise Control: Description and Operation

CIRCUIT OPERATION

The Cruise Control System operates a mechanical linkage to the throttle by means of Vacuum Motor. The motor is a diaphragm. The diaphragm moves when vacuum is applied to only one of its surfaces. A solenoid operated valve connects the Vacuum Motor to a Vacuum Tank. Another solenoid valve vents the vacuum to reduce the suction. The Cruise Control Module controls the Vacuum Motor and the throttle by pulsing these solenoid valves on and off.

One input to the Module is the vehicle speed. This input comes from the Vehicle Speed Sensor. If the actual speed signal is different from the speed that was set into and remembered by the Module, the Module generates pulses to change the vacuum and return the vehicle to the set speed. The Vehicle Speed Sensor is mounted on the transmission. Other inputs to the Module come from the Cruise Switch and the Set Switch. A disengage input to the Module comes from a switch above the brake pedal (and a switch above the clutch pedal with manual transmission). An independent vacuum shut-down of the Cruise Control comes from the Cruise Control Vacuum Release Valve above the brake pedal.

The two inputs of the Cruise Control Module operate the coils of the Vacuum Valve and the Vent Valve. Both valves are located in the Cruise Control Servo. These valves move the throttle by means of the Vacuum Motor. The Servo Position Sensor coil senses the position and motion of the Vacuum Motor. It feeds this information back to the Module to provide smooth acceleration while the vehicle is in Cruise Control.