Speed Control System
When the speed control actuator switch is ON, see Figure , voltage is applied to the ON indicator LED and the speed control (ASCD hold) relay via the RLY COIL fuse. See Figure . The ASCD hold relay energizes and applies voltage to the inhibit relay circuit EJ25 (Green/White) wire and No. pin 15 circuit EJ14 (Green/White) wire of the speed control module. See WIRING DIAGRAMS . The inhibit relay applies voltage to circuit EJ22 (Blue/White) wire to the speed control disengage switch. The speed control disengage switch then applies voltage circuit EJ13 (Yellow) wire to pin No. 16 of the speed control module. With voltage applied to pins No. 15 and No. 16 of speed control module, the system engages and the speed control indicator illuminates. See Fig 1 . When the inhibit relay is energized by the Transmission Range (TR) switch circuit ST03 (Light Green/Black) wire or the speed control disengage switch circuit EJ13 (Yellow) wire is opened, or the brake pedal circuit EJ09 (Green/Black) wire is depressed, voltage is applied to pin No. 20 and voltage is removed from pin No. 16 of the speed control module. This disengages the speed control system.
The speed control module uses the input from the Vehicle Speed Sensor (VSS) circuit EJ10 (Green/Yellow) wire and the speed control switch assembly circuits EJ01 (White/Blue) wire and EJ02 (Blue/Red) wire to decide if the vehicle needs more or less throttle. See WIRING DIAGRAMS . This is accomplished by the speed control module actuating the speed control actuator's vent circuit EJ06 (Orange) wire VAC circuit EJ16 (Brown/Yellow) wire and speed control actuator motor circuit EJ04 (Light Blue) wire. The speed control actuator motor creates a vacuum and the vent lets the air in, which in turn retracts or extends the speed control actuator (cable), thus controlling throttle position and engine speed. The Brake On/Off (BOO) switch signals the speed control module to shut off the speed control but keep speed memory for the resume function.
When the speed control actuator switch is in the OFF position, the ASCD hold relay is not actuated. This prevents voltage from being applied circuit EJ25 (Green/White) wire to the inhibit relay, the speed control disengage switch circuit EJ22 (Blue/White) wire and pins No. 15 and No. 16 of the speed control module circuit EJ13 (Yellow) wire and EJ14 (Green/White) wire. See WIRING DIAGRAMS . This disengages the speed control system.