Principles of Operation

WARNING: This page is about a different car, the 2003 Lincoln Town Car. However, it is still accessible from the selected car via links, so may be relevant.

The speed control system is designed to maintain vehicle speed above 48 km/h (30 mph). After the ON switch is depressed, depressing the SET/ACCEL switch will activate the speed control actuator. To increase a set speed, either depress and hold for continuous acceleration, or momentarily tap the SET/ACCEL switch for 1.6 km/h (1 mph) acceleration increments. To decrease a set speed, depress and hold the COAST switch until the target speed is reached, or momentarily tap the COAST switch for 1.6 km/h (1 mph) deceleration increments. When the speed control system has been disabled by tapping the brake pedal, the RESUME switch can be depressed and the vehicle will return to the original set speed if the vehicle is traveling over 48 km/h (30 mph) and the OFF switch has not been depressed.

NOTE: The deactivator switch is provided as an additional safety feature. Normally, when the brake pedal is depressed, an electrical signal from the brake lamp circuit to the speed control actuator will deactivate the system. Under increased brake pedal effort, the deactivator switch will open and remove power to the speed control actuator clutch, releasing the throttle independently of the speed control actuator logic circuit.

NOTE: The clockspring provides the electrical interface between the steering column wiring and the speed control actuator switches in the steering wheel.

The inputs to the speed control actuator are:

SCP link. The speed control actuator communicates with other control modules using SCP. The vehicle speed, brake pedal position, throttle position, RPM, and PRNDL status is retrieved by the speed control actuator from the SCP link.
speed control actuator switches
deactivator switch

The outputs of the speed control actuator are:

SCP link. The speed control actuator sends an output message through the SCP link to indicate whether the speed control system is ON, OFF, ENGAGED, or DISENGAGED.
speed control actuator cable controlling the throttle position