I have a c320 coupe 2003. When I got it in , it kept showing me a battery and saying to switch consumers off. I took it to a benz service and it took them 3 tries to fix it. It has been fine for about a year now but recently it keeps showing me the battery and saying something like overvoltage/undervoltage(can't remember what it says exactly). I need help because my warranty has expired and if this is a huge problem I need to know so I can get it fixed.

Thanks for the help!

 

Take it in immediately before you need to replace the battery. Chances are that it is only a voltage regulator inside the alternator. Some are not replaceable seperately and the entire alternator must be replaced. Voltage regulator should be $100 + labor of 2-3 hrs as compared to the alternator $600-1000 likely at the same labor rate. There are valeo alternators and bosch units. The bosch voltage regulators have had many problems and the part has been superceeded at least 5 times since '03. I have replaced probably hundreds of them on "e" class 211 chasis and"sl" 230cars due to multiple recalls and failures. Talk with the service manager too and tell him/her about the previous repair issues. Chances are that they may "goodwill" warranty the repair or do a 50/50 split on the repair.