04 C230K Alternator/Battery Warning light...
 

My Alternator/Battery light comes on when the car is cold. It is fine after a few minutes of warming up. Sometimes when I just take off it is real bad. No power to windows, radio, air, lights. My computer even keeps the transmission from shifting gears to it will redline and I would have to pull over. I replaced the battery(not the problem) last year and it seems to only do this in the cold season. Everytime I take it to AutoZone for the Alternator check they say its reading fine. Not sure if anyone else has had this problem but it gets annoying. I finally took it to a European place and left it over night for them to cold start it and it never did it. Other times it comes on and it will leave a malfunction on the computer. But then if I start the car later that day the malfunction is not there.
Any ideas?

Did you get any info? I have the same issue but this year my headlights are burning out!! Think it may be an alternator problem.... Let me know if you found anything out :)

https://mercedesforum.com/forum/general-tech-5/alternator-warning-light-coming-33717/

Check this forum out....this is where you find most of the people talking about it. You will also see what I wrote.

It is the Voltage Regulator on the Alternator. You can change it without changing the entire alternator.

Hope it helps and good luck!

That would make the most sense to me. Apparently my battery just failed the load test so they say I need a new battery. I just don't see how that will solve the headlights burning out in a matter of seconds but I guess they tested my alternator and it is fine... Stay tuned :)

Let me know if the voltage regulator works out for you guys, if not I may have some ideas. If you have a 112 or 113 engine, be careful with the lower section of the timing case cover when you are removing the alternator. If you pry on it wrong it could break and cost you a lot of time and money.

If you know what you are doing then you can change the voltage regulator without taking the alternator out. It is hard to take the alternator out. The voltage regulator is on the back side of it and there is a small plastic shield you have to take off to get to it. That part is not that hard to do, I at least didn't think so.