Ram air suspension operation
The Ram air suspension system replaces the traditional mechanical/pneumatic shock/strut and coil spring system. The Ram air suspension system automatically lowers and lifts the vehicle using an air spring (air-bag) and air shock assemblies. The system automatically adjusts vehicle height based on driving conditions and driver input. The air suspension system works in conjunction with the vehicle’s stability and traction control systems to provide an optimal and safe ride. The air spring and shock assembly are controlled using air pressure and that air pressure is controlled by the air suspension control module (ASCM). The ASCM receives ride height data from the ride height sensors and works with data from the ECM to learn current driving conditions. All communication between the ASCM and ECM are over multiple controller area networks (CANbus). All diagnostics must be performed using a scan tool. The Ram air suspension system uses the following components, sensors and control units:
Ram Air Spring And Shock Assembly
The air suspension spring is an air-bag that performs the job of a convention coil-over spring while also providing the means to adjust vehicle height, depending on driving conditions and driver input.
An air line connects the air spring and shock to the compressor/reservoir/valve block assembly.
Ram air suspension compressor
The compressor assembly is bolted to the vehicle frame on the right side of the vehicle. The air-lines and air suspension hose assembly along with multiple electrical connectors are attached to the compressor assembly.
The compressor itself is suspended from mounting bracket by three spring-loaded studs to reduce vibration and noise. The valve block is bolted to a mounting bracket. The air suspension compressor and the valve block can be serviced separately.
The compressor can’t 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.
Ram Air Suspension Reservoir
Because the air suspension system is a closed system an air suspension reservoir is required to store a specified volume of pressurized air for use when the system needs to raise or lower the vehicle height. If any component of the air suspension system is damaged and air pressure is lost, the reservoir will hold any pressure left in the component.
The air suspension reservoir assembly is mounted under the pickup box assembly. The reservoir contains a fill port and an air-line which is part of the rear air line assembly. The compressor cannot refill the reservoir if all pressure is exhausted as in a compressor assembly or valve block replacement. The system will need to be filled at the reservoir using nitrogen.
Ram Switch Bank — Level control solenoid valve
The level control solenoid valve is mounted on the compressor bracket forward of the rear bumper on the right side and is bolted to the frame. The valve block mechanically controls the flow of air in the system and maintains the pressure in the reservoir, and in each air spring individually. Valves and solenoids in the valve body open and close to increase or reduce pressure to air lines that connect to each pressurized component allowing the system to move each corner of the vehicle up or down as necessary. All wiring connected to the valve block is directly from the Air Suspension Control Module (ASCM) which fully controls the valve body. The ASCM determines pressure from an internal pressure sensor in the valve body.
Air temperature sensor
The air temperature sensor tells the ASCM the ambient temperature in the area of the air compressor for protection against overheating.
RAM Air Suspension Control Module (ASCM)
Controls the operation of the compressor and solenoid valve assembly
Pressurized air is transferred through to the air spring and shock through air-lines that run between the air suspension compressor assembly, air suspension reservoir, compressor assembly valve block, front air suspension spring and shock assemblies, and the rear air springs.
The air-lines are made of nylon and are a one-piece assembly that’s attached to the vehicle frame with a dedicated harness clipped to or run along the vehicle frame.
The air-lines can be repaired for holes or punctures, up to a maximum of two repairs in the entire system.
Ram Ride Height Sensors
The front height sensors are located in the front wheel well areas. The sensors are attached to the frame, and a rod from the sensor is connected to the upper control arm. The ride height sensors are wired directly to the Air Suspension Control Module (ASCM) where the information is used to determine and control vehicle height. The ASCM then transmits the information on the CAN bus. The sensors have three wired circuits for height sensor power, signal and return.
Disable before hoisting or performing service
Always disable the system before hoisting to prevent the Ram air suspension from attempting to adjust ride height as you lift the vehicle. Disable the Ram air suspension by pressing the “Up” and “Down” switches simultaneously for more than 5 seconds. The air suspension system will return to normal operation when the vehicle speed reaches 25 kph (15 mph).
The system also has an auto-disable in the event you forget to manually disable but you should not depend on that system. Working on the vehicle with the system operational can cause possible serious injury or death.
Ram air suspension auto disable
When operating properly, the air suspension system auto-disables when it detects vehicle lift on a frame hoist, or when jacking one corner of the vehicle. During the lift, the system will attempt to change height slightly before realizing you’re lifting the vehicle. It will then switch to auto-disable.
©, 2020 Rick Muscoplat
Posted on by Rick Muscoplat
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