System Operation

Fig. 1 Air suspension system. 1984---87 Continental & Mark VII (1987 Thunderbird turbo coupe system is similiar):

System operation is maintained by the addition or removal of air to or from the air springs, resulting in a predetermined front and rear suspension height. This predetermined height is known as the vehicle trim height. The trim height is controlled by three height sensors, two of which are located at the front wheels and a third at the rear suspension, Fig. 1. The height sensors are attached to the body and suspension arms and will lengthen or shorten, depending on the amount of suspension travel. As weight is added to the vehicle, the body settles, shortening the height sensors. The height sensors signal the control module, which then activates the air compressor through a relay, and signals the air spring solenoids to open. As the body rises, the height sensors lengthen. When the predetermined trim height is reached, the air compressor and solenoid valves are de-activated by the control module. As weight is removed, the body rises, lengthening the height sensors, and the height sensors signal the control module. The control module then opens the air compressor vent solenoid and the air spring solenoid valves. As the body lowers, the height sensors shorten. When the predetermined trim height is reached, the air compressor vent valve and air spring solenoid valves are closed by the control module. The air required for leveling the vehicle is distributed from the air compressor to each spring by four nylon air lines which start at the dryer and end at the individual springs. Each air line is color coded to identify the spring to which they belong. The dryer is used to dry the air before it is delivered to each spring. The air required for compression and the vent air enter and exit through a common port on the compressor head. Vented air is controlled by a solenoid valve in the compressor head. Electrical power to operate the system is distributed by the main body harness. The control module controls the air compressor relay, vent solenoid and the four air spring solenoids to provide the air requirements of the springs. The module also provides the power and ground circuits to the height sensors, while monitoring the input from the sensors and the Ignition Run/Brake and On/Door Open circuits. These inputs are used by the module in determining vehicle leveling requirements, which are then carried out by the air system components controlled by the module. The control module also provides for system self diagnosis, a routine for filling the air springs and operation of the system warning lamp.