Vehicle: 2010 Mercedes Benz C300 (204.054), V6-3.0L (272.947), Automatic Transmission/Transaxle

Mileage: 177,407

Problem: The customer had purchased a new A/C compressor for his Mercedes C300 and asked the shop to install it. The technician Installed the compressor and recharged system. The A/C worked great, but during the test drive, something weird happened. The windshield washer started spraying all on its own, and continued spraying after the ignition key was shut off.

The technician disconnected the battery and let the vehicle sit overnight. The next day, he reconnected the battery and started the engine. Now, the A/C wouldn’t work, the lights would not turn off, and scan tools would not communicate with the vehicle. It was like the vehicle was haunted!

A call went out to the ALLDATA Tech-Assist for some diagnostic help with this unusual and quite possibly paranormal activity. The ALLDATA Tech-Assist consultant listened to all the issues that occurred and then said calmly, “Yeah, I’ve seen these problems before.

"The car isn’t haunted. Most of the time, when a Mercedes starts acting like this (no communication, wipers, headlights go on and off etc.), there’s usually moisture and/or corrosion in the front signal acquisition module (SAM) connectors. Another common location is the controller area network (CAN) voltage distributor connector on the driver floor panel, especially connector X30/30”.

Confirmed Repair: When the technician removed the cover, he immediately identified a few connector pins that were corroded (See image). He cleaned the connector pins and rechecked all connectors in that area. After the repairs, no more weird issues occurred, and the A/C worked great. Problems solved!