If your car has AIRMATIC
Reported across every platform once past roughly 100,000–120,000 kmThe car sitting low on one corner or at one end overnight, a compressor running and running, or an AIRMATIC warning on the dash.
Almost every AIRMATIC fault traces to one of four things: a leaking air strut, a worn-out compressor, a stuck relay, or a failing ride-height sensor. They are not interchangeable diagnoses and they are not the same money. A relay is the cheapest thing on that list and is worth eliminating first — on the W211 it is the 40 amp K67 AIRMATIC relay at position F74 under the bonnet. A compressor that has been working against a leaking bag for months usually needs replacing alongside the bag, so a car with one corner down is often a two-part job, not one.
Parts this needs
Checked against fcpeuro.com

