Mercedes-Benz W220 ignition key won't turn or starter only clicks
W220 key won't turn in the ignition and there is no power, what is wrong?
The cause can be a blown fuse: the ignition switch and the central locking share a fuse, which can blow, for example, from a short circuit in the alarm siren. The fault can also be in the key, where the coil inside has come loose from its solder joint. Check the key before replacing the lock.
W220 starter only clicks or the instrument cluster is dark, what should be checked?
First check the battery and the ground connection between the engine and the body, for example by testing with a jumper cable. If the starter relay clicks, measure the control wire all the way to the starter. A loose connection in the fuse and relay box in the engine bay can also cause the symptom.
The battery is flat and the starter only clicks, how do I proceed?
Charge the old battery or replace it with a fully charged one. Charge the battery with the terminals disconnected so the car does not draw current during charging. Use a charging cable that is thick enough, because a thin cable heats up and is not sufficient.