AUTOMATIC AIR SUSPENSION

GENERAL INFORMATION

This system provides automatic height control and low spring rates to improve suspension characteristics of the vehicle. And it will automatically level the front and rear of the vehicle. It will also maintain the optimum vehicle attitude from one passenger through full vehicle load.

The automatic air suspension system includes the following components:

²Compressor/air dryer assembly

²Compressor relay

²Front struts

²Rear springs

²Rear shocks

²Control module

²Air lines

²Compressor

²Rear height sensor

²Wiring harness assembly

²Compressor cover

Front springs (and height sensors) are integral with the shock absorber strut assemblies. While rear air springs replace conventional steel units. Rear height is controlled via a height sensor contained within the right rear shock absorber. Solenoids (integral with each air spring) control air volume/pressure requirements. Pressurized air is distributed from the air compressor/dryer assembly and routed to each air spring by four separate air lines. The air lines start at the dryer and terminate at the individual air springs. The system is monitored and controlled by the Air Suspension Control Module (ASCM) (Fig. 1).

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FRONT AND REAR AIR SPRINGS

The front and rear air springs are essentially pneumatic cylinders that replace the steel coil springs. The air filled springs allow the vehicle suspension height to be adjusted for all weight conditions.

The air springs allow for the reduction of spring rates to improve vehicle ride characteristics.

FRONT/REAR SPRING SOLENOIDS

The front and rear solenoids control air flow in and out of the front and rear springs. The Air Suspension Control Module (ASCM) opens the solenoids when the system requires air to be added to or exhausted from the air springs. The solenoids operate at a current draw range of 0.6 to 1.5 amps.

HEIGHT SENSOR

A magnetic switch type sensor. Located in the right rear shock absorber and left and right front struts, (Fig. 2) monitors vehicle height. The sensors transmit signals to the (ASCM) relating to vehicle height status (low, trim, medium, high).

CONTROL MODULE

The Air Suspension Control Module (ASCM). Is a device that controls the ground circuits for the Compressor Relay, Compressor Exhaust Solenoid Valve and Front and Rear Solenoid Valves. The (ASCM) limits the compressor pump operation time to 170 to

SUSPENSION/DRIVESHAFTS 2 - 75

190 seconds. This controlled operation time is to prevent damage to the compressor motor.

To prevent excessive cycling between the compressor and the exhaust solenoid circuits during normal ride conditions. A 14 to 16 second delay is incorporated in the microprocessor logic.

The system is non-operation when one of the following conditions exists. A door(s) is/are open, the trunk is open, the service brake is applied or the throttle position sensor is 65% to 100% open. System operation is inhibited during high speed cornering activities or if there is a charging system failure. The control module is on the CCD bus system.

COMPRESSOR ASSEMBLY

The compressor assembly is driven by an electric motor and supplies air pressure between 930 to 1241 kPa (135 to 180 psi) (Fig. 3). A solenoid operated exhaust valve. Located in the compressor head assembly, releases air when energized.

A heat actuated circuit breaker. Located inside the compressor motor housing. Is used to prevent damage to the compressor motor in case of control module failure.

COMPRESSOR AIR DRYER

The air dryer is attached to the compressor (Fig. 3). This component serves two purposes. It absorbs mois-