When the ignition is switched on, or when the vehicle’s door is opened before ignition, the control system is activated. The height sensor uses the induction principle to constantly monitor the distance between the vehicle’s axle and its chassis.
When the vehicle is being loaded, unloaded, or lowered due to driver command or vehicle speed, the electronic readings from the height sensor monitor the change. This is picked up by the electronic control unit and compared to the stored reference values.
The ECU either activates the electric motor of the compressor, or the exhaust solenoid valve. This also requires the solenoid valve block to be actuated, in order to maintain the required level. The corner solenoid valves are subject to stringent leakage requirements to maintain the vehicle’s height even without system operation.
When the vehicle is being loaded, the compressor delivers air into the four air suspension bellows, until the normal level has once again been reached. For additional air delivery or rapid response, the reservoir solenoid valve is opened and air flows directly from the reservoir.
When the vehicle is being unloaded, the solenoid valve block is activated. This results in airflow from the air suspension bellows being removed via the air dryer solenoid valve in the compressor, then via the relay valve. The air is then exhausted into the atmosphere.
Any dynamic air spring movement while the vehicle is in motion is ignored and does not cause the control system to respond.