Cruise Control: Description and Operation

The Integrated Vehicle Speed Control (IVSC) system for these models consists of operator controls, a servo (throttle actuator) assembly, a speed sensor (Models with non-electronic instrument cluster only), a clutch switch (Manual Trans.), stop lamp switch, vacuum dump valve, horn relay, two check valves, aspirator (except Cougar and Thunderbird), and necessary wires and vacuum hoses. On models with an electronic instrument cluster, the electronic speedometer assembly generates the speed signal and therefore does not require a speed sensor.

The speed control amplifier assembly function is integrated into the EEC-IV Electronic Control Assembly (ECA). The servo assembly is mounted in the engine compartment and is connected to the throttle linkage with an actuator cable. The servo is also connected to an aspirator and a manifold vacuum source through check valves. The speed control sensor is located on the transmission.
The aspirator is connected to the thermactor air pump and is used to improve speed control performance when engine load is high. The check valves switch the servo's vacuum source from the manifold to the air pump according to which has the strongest vacuum signal available. The check valves also keep vacuum from leaking back into the source not being used.
The vacuum dump valve provides an additional safety feature in the system. Normally, when the brake pedal is depressed, an electrical signal from the stop lamps to the ECA will turn off the system. In addition, the vacuum dump valve will mechanically release the vacuum in the servo when the brake pedal is depressed. This releases the throttle independently of the ECA control.

ACTIVATION

To operate the speed control system, vehicle speed must be no less then 26 mph for all models except Sable and Taurus with 4-153/2.5L engine, or 35 mph for Sable and Taurus models with 4-153/2.5L engine. Activate the system by pressing the ON switch on the steering wheel, then depress and release the SET ACCEL switch. This will result in the current speed being maintained until a new speed is set by the operator, the brake or clutch pedals are depressed, or the OFF switch is depressed.

DECREASING SET SPEED

The vehicle speed may be reduced by applying the brake or clutch pedal and then resetting the speed using the forgoing method or by depressing the COAST switch. When the vehicle has slowed to the desired speed, the COAST switch is released and the new speed is set automatically. If the vehicle speed is reduced below 30 or 25 mph (as stated previously), the operator must manually increase the speed and reset the system.

INCREASING SPEED

The vehicle set speed may be manually increased at any time by depressing the accelerator until the higher speed is reached and stabilized, then depressing and releasing the SET ACCEL button.
Speed may also be increased by depressing the SET ACCEL switch button at speeds over 30 or 25 mph (as stated previously) and holding it in that position. The vehicle will then automatically increase speed. When the desired rate of speed is attained and the button is released, that new set speed will be maintained.

RESUME

When the speed control system is deactivated by depressing the brake or clutch pedal, the set speed prior to deactivation may be re-established by holding the RESUME switch for two seconds. The RESUME switch is hinged on the side closest to the SET ACCEL switch. Therefore, it should be depressed on the side farthest from the SET ACCEL switch. The resume feature will not function if the system is deactivated with the OFF switch, if the vehicle speed has been reduced to below 30 or 25 mph (as stated previously), or if the ignition switch is turned off.