2001 Audi Allroad Quattro Active Suspension Air Spring Control Solenoid Replacement Cost

Vehicles with air ride suspension use air bags, or air springs, instead of metal coil springs. These allow for variable ride height, automatic leveling, and a very comfortable ride. The drawback is that there must be a system to maintain the amount of air going in and out of the system, and the controller for this system is the air spring control solenoid.

There are two different types of air spring control solenoids. The unit may have solenoids for each airbag installed in one location, or the control solenoids may be located at each wheel. Though these components are located in different positions, they still operate the same way. Either the air bag control solenoids respond to input from the ride height sensors or air pressure sensors by opening valves to let air pressure into the air bag, or relieve pressure from the air bag. This will change the ride height, level the vehicle automatically, make the suspension more or less firm, and stabilize the vehicle.

When the airbag control solenoid fails, the vehicle may not level properly, the vehicle may ride too high or too low, the ride may become unstable, and the driver will be prompted for service by a warning light specific to the manufacturer of the vehicle. Also, vehicles with driver adjustable active suspension systems will notice they are unable to adjust the suspension, or adjusting the suspension does not result in the desired end state.

This issue should be repaired immediately, even in cases where the vehicle simply fails to adjust. Driving with a faulty air bag control solenoid can cause severe instability, quick and unexpected changes to the vehicle's ride height at any wheel, and damage to one or more of the air springs.

Air spring control solenoids mostly fail on older vehicles, however, if the air compressor fails, debris in the system may cause early failure. In general, solenoids are reliable components, and tend to last for many years.

When the air suspension is having an issue, the seasoned technician will have a good idea of the issue before inspecting the active suspension system. When noting that the suspension will not raise or lower at one or more wheels, the technician will likely test the height or pressure sensors with a diagnostic scan tool, followed by the air bag control solenoids. If the solenoids do not actuate on command, the solenoid circuit will be tested for proper operation before replacing the airbag control solenoid.

Replacing an air bag control solenoid may require replacing them all as a whole, or replacing only the defective solenoid. In nearly all cases, the solenoid and valve are the same component. First, the active suspension system is deactivated, and air bags are deflated. Then, the solenoid or solenoids needing replacement are disconnected electrically and pneumatically. The pneumatic line ends are cleaned, and, if needed, a sealant is applied before securing the new solenoid. Once installed, the solenoid will be tested once again for function when commanded by a diagnostic scanner.

Any time the air suspension system is opened, it should be purged of air before reclosing the system. This will help rid the system of moisture caused by humidity and condensation. Also, this will allow the technician to monitor for debris, and take action if needed.

When diagnosing any active suspension system, the suspension must be deactivated before raising the vehicle with a jack. When the vehicle is lifted, the active suspension will attempt to level itself if left on, and this may result in damage to the active suspension system, or unstable lifting with the jack. If deactivating the system is not possible, disable the compressor.

Nearly anyone could diagnose and repair a failed active suspension air bag control solenoid, but the proper tooling will drive many from attempting the repair. Since fast detection of faulty components requires the use of a diagnostic scan tool, most owners will take the vehicle to a professional rather than purchase expensive software and connectors. If the problem is known, the average DIYer can easily replace the solenoid with only the assistance of the vehicle specific service manual.