Mercedes-Benz W212 won't start although the key turns
The W212 won't start although the key turns and power works, what is the cause?
Often the fault is a small relay in the fuse box. The relay can close late or stay stuck, so the starter does not work or starting is delayed. Replacing the relay has fixed the fault, and Mercedes has issued a bulletin on replacing two micro relays in the front fuse box. Check the fuses as well.
Fuse 7 (20 A) has blown, what does it mean?
Fuse 7 protects the starter control circuit. When it has blown, the key turns but nothing happens. Replacing the fuse fixes the situation, but if it blows repeatedly, the fault is probably in the starter and the starter must be replaced.
The starter cannot crank and the instrument cluster lights dim, what causes this?
There is a voltage drop between the battery and the starter. The cause can be a poor cable or connection, a short to ground in the starter or worn starter parts. An overheated cable may belong to the wiring harness, so let a workshop assess the repair.