I buy the car (03 SL500) with deaer telling me he replaced BOTH batteriess and THEN the red light on dash came on when you turn the key.....
two weeks later the battery goes dead/no start condition. I charged the battery,put a voltmeter to the engine compartment battery and it shows only 126 volts....apparently thevoltage regulator or alternator are bad, right??? Wel, we cahnge BOTH of those and STILL have the red light/visit shop light and STILL have 12.6 at the battery with car running? ANyne know what the gremlin is? I'm being told maybe the battery control module in trunk...
thanks in advance,
Tony R.

 

me/be dealership comes through: replaced completely fried battery control module PLUS 200 amp pre-fuse below pass. floor.
Ubelievable. hope this helps someone else.

 

I have the same issue, however, both batteries have been checked out ok, and no alternator charge issues either. Does anyone have any knowledge as to why my red battery light keeps coming on after every start? Any assistance is appreciated.

 

does anyone have the answer to this
'

 

did you ever get a response

 

Did you figure the problem with your Mercedes?