A common problem we often see on Mercedes-Benz with airmatic air suspension is that the ride quality is very rough and stiff.
The most common problem that makes a Mercedes-Benz with AirMatic suspension ride very rough is due to faulty Adaptive Daming System solenoid, also known as ADS solenoid. There are four ADS valves, one connected to the side of each air suspension strut (shock absorber). In most cases, to fix the problem, the strut itself needs to be replaced because the ADS valves can not be removed.
When there is a suspension problem and the damper valves for ADS are no longer controlled, the suspension is switched to the "hard" damping level. A fault code is stored in the AIRmatic control unit that can help you determine what is wrong.
Common complaints that we hear from owners include:
- Suspension seems bouncy
- Ride quality is very rough
- The sport mode button stays ON
- Can not switch suspension to COMFORT
- Suspension is stiff
- Airmatic malfunction message
- Sometimes there may be no airmatic error message other than the Sport/Comfort button staying always on.
The most common problems that cause rough ride on a Mercedes-Benz with air suspension are:
Faulty ADS Level Control Valve
Each air strut (shock absorber) has one ADS level control valve connected to the side, also known as ADS solenoid. These are four ADS valves on a Mercedes-Benz with airmatic suspension.
- Y36/6y2 - Right front level control valve
- Y36/6y1 - Left front level control valve
- Y36/6y3 - Left rear level control valve
- Y36/6y4 - Right rear level control valve
The most common problem is that one of these ADS valves fails. To fix the problem, you will need to read the codes from the air suspension module. Once you know which code valve is faulty, you will need to replace that air strut. Unfortunately, the ADS valves can not be removed from the strut. The only repair you can possibly do if the wire is damaged. If the valve itself is faulty, you will have to replace the whole air (bag) strut.
Do not replace the air suspension strut without making sure it is faulty. Disconnect the connector for the air suspension strut and check the resistance between the pins. There are three pins in total. Resistance values should be either 11 ohms or 22 ohms.
The wires for each air suspension strut run from the Airmatic Module to the air strut. These wires can get corroded. Also, the connector where the ABS and air suspension wire connect can get loose or corroded. To access the connector, you will need to remove the wheel liner.
AirMATIC Suspension Control Module / N51
Lastly, in a few cases, we have vehicles where the problem was the airmatic module. In this case, the air suspension was stuck in SPORT mode. After reading the fault codes, we were getting an error code for a faulty left rear air suspension strut.
We checked the resistance for the strut, which was correct. We decided to replace the strut, but the fault code was still there. Next, we checked the connectivity of the wires from the rear air strut to the wires, and the wires were fine. The only possible failure, in this case, was a faulty air suspension control module, even though the code was pointing to the air strut.
Replacing the air suspension control module solved the problem. Airmatic control module location can vary between models. On a Mercedes-Benz S-Class W221, the N51 module is located at the front passenger footwell. On an E-Class W211, the airmatic module is located in the trunk under the spare tire.
Other possible problems that can cause a rough ride on a Mercedes-Benz include:
- Acceleration/Ride height sensors
- Faulty SAM Module
- Airmatic valve block
- Airmatic compressor
- The faulty compressor relief valve
- Battery voltage below 9 volts
- Overinflated low profile tires
If your Mercedes-Benz rides very rough, the suspension is stiff and stuck in SPORT mode; the most likely problem is a faulty ADS level control valve at one of the air struts. Other possible issues include damaged wires or a faulty N51 control module.
This problem can affect any Mercedes-Benz vehicle with air suspension (AirMatic), including E-Class, ML-Class, CLK-Class, GL-Class, or any other model.