Cruise Control: Description and Operation

The Cruise Control System operates a mechanical linkage to the throttle by means of a Vacuum Motor (Cruise Servo). This is a diaphragm moved by a vacuum applied to one side. 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 Buffer. If the actual speed signal is different from 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. Other inputs to the module are from the Cruise Switch and the Set Switch. A disconnect input to the module comes from a switch on the brake pedal. A separate vacuum shutdown of the Cruise Control comes from the Brake Cruise Release Valve on the brake pedal.

The two outputs 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.