Hi everybody,

Recently these 2 malfunctions have been showing up on the MFD in my W211:

RED - “BATTERY/ALTERNATOR – VISIT WORKSHOP"
and simultaneously
WHITE - "ELECTRICAL CONSUMER SWITCHED OFF"

I read somewhere that these 2 messages together usually mean that either one of these 4 situations occurred:
• battery control unit (N82) is defective
• the alternator (G2) is defective
• the additional battery relay (K57/2) is defective
• additional battery (G1/7) are defective.

In my case I think it’s the last one, because if I drive long enough the battery gets charged and the error messages disappear. If I leave the car parked for over 24 hours these messages reappear the next time I start the car. Btw, the car always starts up fine (almost immediately)

Am I correct to assume that the aux battery (the small one under the hood) is going bad?

Does anybody know the part number for this battery?

Is there a Varta or Bosch equivalent? Or am I stuck with the dealer?

Thanks,
Miguel

 

Your 4 choices are correct and to correctly pinpoint it, i would suggest a midtronics test.

 

He's right. Avoid spending money on the wrong "cure". Its an easy quick test. ... and accurate.