System Operation

Fig. 7 Height sensor operational test:

RAISING THE VEHICLE
When weight is added to the rear of the vehicle, the body is forced downward which has the effect of rotating the height sensor actuating arm upward, Fig. 7. This causes the height sensor to electrically start the internal time delay circuit. When the time delay has occurred, the sensor completes the compressor relay circuit to ground. With the relay energized, the 12 volt circuit to the compressor is completed and the compressor runs, causing the shock absorbers to inflate. As the air shocks inflate, the body moves upward and starts rotating the height sensor actuating arm back toward the position the arm had prior to the weight addition. When the body reaches the original trim height within ±3/4 inch on 1982---85 models, or 1 inch on 1986---87 models, the sensor opens the compressor relay circuit shutting off the compressor.
LOWERING THE VEHICLE
When the weight on the rear of the vehicle is removed, the body immediately moves higher. This high condition has the effect of rotating the height sensor actuating arm downward, Fig. 7. The height sensor then senses the high condition and starts the time delay circuit. When the time delay has elapsed, the sensor then completes the exhaust solenoid circuit to ground. With the exhaust solenoid energized, air starts exhausting out of the shocks back through the air dryer and exhaust solenoid to atmosphere. As the body moves downward, the height sensor actuating arm is rotated toward its original position (position before weight was removed). When the vehicle reaches its original height within ±3/4 inch on 1982---85 models, or 1 inch on 1986---87 models, the sensor opens the exhaust valve solenoid circuit, preventing the air from further escaping. A minimum air pressure of 14---20 psi on 1982---85 Eldorado, Toronado, 1982---86 Riviera, 1982---85 Seville and 1985 DeVille and Fleetwood, 7---14 psi on 1985---87 Electra, Park Avenue, 98, 1986---87 Toronado, Brougham, Eldorado, Seville and 88 and 1987 Bonneville, 15---22 psi on 1986---87 DeVille and Fleetwood or 8---15 psi on all other models is maintained in the shocks by the air dryer retention valve. The minimum pressure provides improved ride characteristics when the vehicle is at minimum loading.



AIR REPLENISHMENT CYCLE
The air replenishment cycle occurs only on some 1985---87 models. When the ignition is turned on, height sensor position is checked. If position of the sensor indicates that it is not necessary to raise or lower the vehicle, an internal timer circuit is activated. After 40 seconds, the ``Car Is Leveling'' light is illuminated and compressor is activated for 4 seconds to supply struts with sufficient residual pressure. If, during the 40 second delay, weight is added to or removed from the vehicle, the air replenishment cycle is overridden and the system will raise or lower the car after the normal height sensor time delay.