Mercedes-Benz W220 Airmatic compressor won't start or keeps running: relay and fuse
S500
W220 Airmatic compressor won't start, what should I check first?
Start with the fuse and relay, then the wiring and the compressor's electrical connector. The connector can oxidise and break. A cracked intake pipe can also let debris into the compressor and destroy it.
Where are the W220 Airmatic compressor fuse and relay?
The compressor fuse is 40 A and is in the right-side fuse box. The relay is in the passenger-side fuse box in the engine bay and is marked O. The fuse can be on either side of the relay, so check the position from the diagram.
Why does the W220 Airmatic compressor keep running after the ignition is switched off?
A typical cause is burnt relay contacts that have welded shut. When the relay is replaced with a new one, the droning stops.
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