auxiliary battery malfunction

[Drey27]

Hi All,

My car sat with the dealership for 2 months and after received the car back I got a "auxiliary battery malfunction mercedes" on the dash and so I thought maybe it needed charging or replacing. I did some check to see the condition of the battery and the volt meter is showing a good state of charge of 12.6V and I also hooked it up on the charger which then gave a Full Charge reading. I plug the car onto a rearder and it has given

C073300, "Read fault memory of control module. "N10 ( SAM Control Module)"
B1E211B, "The buffer battery has a malfunction. The limit value for resistance has been exceeeded."

I've wire brushed the contacts but the same error keeps coming back.

My question is, is the voltage reading not a good indicator to wether the battery is still in a good state of health, or should I be check something else within the car?

Many thanks.

 

[Diesel Benz]

Which car is it? Cannot be the 2008 CLC?

I replaced the (12 Ah) AUX battery from my W222 twice for the same fault code. The old battery had perfect voltage when not loaded, connecting a 21 W bulb and the voltage dropped several volts (cannot remember exact figures).

 

[Drey27]

Apologies, I need to update my profile, its on an E class coupe 2015.

I guess I would just be replacing it and see how that goes. Thank you.

 

[Ted]

Open circuit voltage is not necessarily an indication of a good battery. You would need to have it load tested.

 

[Drey27]

Open circuit voltage is not necessarily an indication of a good battery. You would need to have it load tested.

will do that! Many thanks

 

[C320]

Check your main 12v battery too. When mine hit 8 years of age it was not keeping the aux battery charged!

 

[Drey27]

Check your main 12v battery too. When mine hit 8 years of age it was not keeping the aux battery charged!

I had the main battery replaced not so long ago.

I am wondering if the white font 4 number on the middle top surface of battery is the week and year (i.e. 46 15) of when the battery is built similar to the engraved code on the battery terminal on main battery? I have a feeling that my auxilary is original battery.

 

[C320]

The first digit from the left is a letter. It stands for the month of the year. A = January; B = February; C = March, etc. The second digit from the left is the year the battery was shipped from the factory. 4 = 2004, 5 = 2005, 6 = 2006, 7 = 2007, 8 = 2008, 9 = 2009, 0 = 2010, 1 = 2011, 2 = 2012, etc.

Source: elsewhere