System Operation

Vehicle's rear vertical height is measured by 2 position sensors. Position sensors convert rear height measurement to an analog voltage read by RSS control module. RSS control module determines if ELC system should exhaust or compress rear air adjustable shock absorbers, or if no action is required. To exhaust ELC system, RSS control module switches low-side of exhaust solenoid valve to ground. To compress ELC system, RSS control module switches low-side of compressor relay coil to ground. Air compressor is enabled only when ignition is on and is activated when a sufficient amount of weight is added to vehicle. Exhaust solenoid valve is enabled at all times and is activated when weight is removed from vehicle.

To ensure system is operating with at least minimum air pressure, an Air Replenishment Cycle (ARC) is commanded each time ignition is turned on. ARC involves the exhaust solenoid valve being energized 20 seconds after ignition is turned on, the air compressor activates 1.3 seconds after the exhaust solenoid valve is energized, the exhaust solenoid valve is de-energized .5 second after the air compressor is activated, and then the air compressor is deactivated 3.2 seconds after the exhaust solenoid valve is de-energized.

To reduce current draw during air compressor activation, RSS control module performs an air compressor head relief sequence before air compressor operation. Head relief sequence reduces air pressure in air compressor cylinder during start-up. Sequence involves the exhaust solenoid valve being energized, the air compressor activates 1.3 seconds after exhaust solenoid valve is energized, and then exhaust solenoid valve is de-energized .5 second after the air compressor is activated.