Mercedes-Benz W212 air suspension: rear won't rise although the compressor runs
The W212 S212 rear won't rise although the compressor runs, what can cause it?
Air either cannot build pressure or cannot flow to the air springs. The cause can be a leaking or stuck valve block, a faulty level valve, the compressor's internal valve or an unfinished height calibration. It is worth replacing the compressor filter and hose at the same time.
Why won't the rear rise in freezing weather and a Malfunction message appears?
Moisture that has entered the system can freeze in the dryer or the drain valve, so the pressure cannot get through. In a warm space the ice melts and the rear rises. If there is water in the system, replacing the air filter alone is not enough; the dryer granules must be replaced.
What should be checked on the electrical side when the S212 rear won't rise?
Check the compressor and level control fuses and the compressor relay on the left side of the luggage compartment. A common fault is a broken wire where the wiring bundle bends inside the underbody plastics, or a chafed wire of the pressure relief valve.
Does a fault code reset alone remove the fault?
Not always. An unfinished height calibration shows up as a fault, and a reset does not remove it. The system does not raise the rear until the calibration has been completed with a diagnostic tool, so let a workshop do it.