I found this on "Cummins Forum". Really helped me better understand our air systems. I was told I had nitrogen, but now I wonder. I own a semi that doesnt have a closed system. If my rams air system has an air dryer, then I have an open system.
Sep 12, 2015 Heavysledz
I found this over on TDR:
From Chrysler Tech Authority:
"The air suspension system is an open system. The air suspension reservoir stores a specified volume of pressurized air for use when the system need to raise or lower the vehicle height. If an individual pressurized component of the air suspension system is damaged and air pressure is lost, the reservoir will hold any pressure left in the component. A scan tool is used to evacuate the component. After repair or replacement of the component, a scan tool can be used to refill the component from the reservoir.
The compressor cannot refill the reservoir and complete system if all pressure is exhausted, as in a compressor assembly or valve block replacement. The system will need to be filled at the reservoir with nitrogen. For complete filling of the air suspension system after a repair (Refer to 17 - Rear Suspension/Standard Procedure) ."
"The rear height sensors are wired directly to the Air Suspension Control Module (ASCM). The rear vehicle ride height information is used to determine and adjust the rear vehicle ride height. The ASCM then transmits the information on the CAN bus to the Air Suspension Unit (ASU). The rear height sensors have three wired circuits: height sensor power, signal and return."
"The Air Suspension Unit (ASU) is made up of two primary components, the compressor and the valve block. There is a single pressurized air line between the compressor and the valve block to maintain system pressure. Control of the air compressor and valve block is from the Air Suspension Control Module (ASCM). Diagnose the air suspension system using a scan tool.
Air Compressor The compressor runs to maintain air pressure any time the vehicle height is being changed or in the event of a small reduction in over all system pressure. Integrated reversing valves in the air compressor allow pressurized air to be moved in two directions, making this a closed system. There is a desiccant located inside the compressor for moisture protection, and an air suspension hose assembly attached to the air compressor (including a filter) which are not pressurized, and can be replaced as an assembly. If water is visible in the filter, the air suspension hose assembly and the valve block must be replaced. An air suspension temperature sensor is attached to the air compressor bracket to monitor ambient air temperature for protection of the compressor.
Positive voltage is from a 40-amp fuse located in the PDC, and a normally open compressor relay (ASCM controlled) located in engine compartment area, and ground for the relay and compressor are through a bolted on eyelet connection.
Valve Block The valve block controls the flow of air in the system and to maintain the pressure in the in each air spring which allows the system to move each corner of the vehicle up or down as necessary. Valves and solenoids in the valve body increase or release pressure to air lines that connect to each pressurized component. The ASCM determines pressure from an internal pressure sensor in the valve body. The air lines connected to the valve block are labeled for individual replacement"
