Automatic Level Control System Operation w/o Road Sensing Suspension

When a load is added to the vehicle, the vehicle body moves down causing the sensor actuating arm to rotate upward. The upward arm movement activates an internal timing circuit and, after an initial fixed delay of 17 to 27 seconds, the sensor provides a ground to complete the compressor relay circuit. The 12V (+) circuit to the compressor is then complete and the compressor runs, sending pressurized air to the shock absorbers through the air tubes.

As the shock absorbers inflate, the vehicle body moves upward rotating the actuating arm towards its original position. Once the body reaches its original height, +/- 25 mm (+/- 1 in), the sensor opens the compressor relay circuit, and the compressor is turned off.

In order to reduce current draw during air compressor starting, the height sensor performs an air compressor head relief sequence before air compressor operation. This sequence reduces the air pressure in the air compressor cylinder during start-up. The air compressor head relief sequence occurs as follows:

When a load is removed from the rear of the vehicle, the body rises, causing the sensor actuating arm to rotate downward. This again activates the internal timing circuit. After the initial fixed delay, the sensor provides a ground to complete the exhaust solenoid circuit, energizing the solenoid. Now, air starts exhausting out of the shock absorbers, back through the air dryer and exhaust solenoid valve, and into the atmosphere.

As the vehicle body lowers, the actuating arm rotates to its original position. When the vehicle body reaches its original height, +/- 25 mm (+/- 1 in), the sensor opens the exhaust solenoid circuit, which closes the exhaust solenoid and prevents air from escaping.

The sensor actuating arm position is checked when the ignition is turned on. If the sensor indicates that no height adjustment is needed, an internal timer circuit is activated. After about 35 to 55 seconds, the compressor is turned on for 3 to 5 seconds. This ensures that the shock absorbers are filled with the proper residual pressure. If weight is added to or removed from the vehicle during the time delay, the air replenishment cycle is overridden, and the vehicle rises or lowers after the normal delay.

Automatic Level Control System Operation with Road Sensing Suspension

When a load is added to the vehicle, the vehicle body moves down causing the sensor actuating arm to rotate upward. The upward arm movement activates an internal timing circuit and, after an initial fixed delay, the CVRSS control module provides a ground to complete the compressor relay circuit. The 12V (+) circuit to the compressor is then complete and the compressor runs, sending pressurized air to the shock absorbers through the air tubes.

As the shock absorbers inflate, the vehicle body moves upward rotating the actuating arm towards its original position. Once the body reaches its original height, +/- 25 mm (+/- 1 in), the compressor relay circuit is opened and the compressor is turned off.

In order to reduce current draw during air compressor starting, the CVRSS control module performs an air compressor head relief sequence before air compressor operation. This sequence reduces the air pressure in the air compressor cylinder during start-up. The air compressor head relief sequence occurs as follows:

When a load is removed from the rear of the vehicle, the body rises, causing the sensor actuating arm to rotate downward. This again activates the internal timing circuit. After the initial fixed delay, the CVRSS control module provides a ground to complete the exhaust solenoid circuit, energizing the solenoid. Now, air starts exhausting out of the shock absorbers, back through the air dryer and exhaust solenoid valve, and into the atmosphere.

As the vehicle body lowers, the actuating arm rotates to its original position. When the vehicle body reaches its original height, +/- 25 mm (+/- 1 in), the exhaust solenoid circuit is opened, which closes the exhaust solenoid and prevents air from escaping.

An air replenishment cycle (ARC) is commanded after each ignition-ON cycle. The purpose of the ARC is to ensure that the ALC system is operating at or above minimum air pressure (residual air pressure). The ARC occurs as follows: