Battery warning light - while driving

[cellarmerc]

When driving home the display suddenly lit up ( e320 cdi 2005 ) in red with a battery symbol and GO TO GARAGE !, I continued to drive on with no apparent failures. When I stopped the car at my house I turned off the engine and restarted it but the warning symbol still appeared. The next day on starting the engine it didn´t give the battery symbol warning light - any ideas why it would have come on while driving ! I first thought alternator failure or belt broken or battery not holding charge. Its true the car has not been driven much lately and its been cold but the warning light came on after 12 miles of driving and while driving the car at 70mph .

I will go to garage but the mechanic charges me Euro75 just to look at it with his Mercedes diagnostic machine.

Many thanks for any comments that would enlighten me.

Tony

 

[davemittell]

Check battery first of all a poor battery can cause this due to voltage drop issues. Or poor connections. Get these checked and cleaned. If not it will be the alternator itself. Mercedes are very sensitive to the voltages so throw lights on for fun!
Recently had a customer with this exact problem and ended up changing the alternator as it was charging at 13 volts some of the time due to worn brushes. Battery wasn't much good either so changed that too.

 

[Sriandy]

Mb tech here and from experiance Id say you need it checked as the sbc aux battery can put the red light on but the alternator can be charging and be ok. Get codes checked.

 

[gandalf]

what is a sbc aux battery and where is it positioned

 

[Terry_]

The sbc aux battery is underneath the pollen filter housing NSF under the hood.
There are many possibilities including the bcm that will cause this warning.
You should check the standing voltage at both the batteries and charge rate.
If the alternator/ reg pack has failed you can find out by checking the voltage directly off the back of the alternator with the engine running

 

[Deleted member 55947]

I had the same problem and it turned out to be the aux battery