2003 Mercedes C320 coupe. Car died on my way home last week. Had it towed to my mechanic. He replaced alternator and upon my request the battery (pushing 7years old). Now the car runs great but can get my Battery/Alternator warning off the screen. I dont get the undervoltage and have left my car sitting for 3 days. It starts right up and runs like a dream. How can I get that battery/alternator warning off? My mechanics diagnostics show no errors. Is their something I can try. Im running out of money for this problem.
Hi ddansvob-
Most of the codes for Mercedes C320's can be cleared (at least temporarily) by disconnecting the negative terminal of the battery and leaving it disconnected for at least 1 minute. I would give it several minutes just to be sure.
There is also a reset procedure that you can use that involves disconnecting the battery, turning the ignition to position 1 several times and then reconnecting the battery. That procedure can be found with a google search.
Possibly the easiest way though is to visit an Autozone or other similar store that has an OBDII scanner that they will use for free on your car, and have them reset the codes. If there is an actual issue with a sensor, etc. though, the code will come back up after the car has been started a time or two. If that is the case, you are going to have to troubleshoot the actual cause of the code, involving finding a Mercedes shop that will help you with identifying what sensor(s) are causing that code to show up.
If your mechanic used non-OEM parts/battery, that is very likely to be the source of your problem. Assuming that they didn't do that (which would be unusual for any mechanic to do), you are likely looking at replacing a voltage sensor or part of the voltage regulating/distribution system. If you get to that, you are REALLY going to need an experienced Mercedes mechanic.
Good luck!
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