W211 Red Battery error message

[grahamwoodward]

Hi guys. Recently I had a red battery - visit workshop error appear on the dash of my 2004 W211 E320 petrol V6 (153,500 miles). The battery was replaced with a genuine Merc battery in late 2017 but as the car is now 18 years old, last week I replaced the original factory-fitted alternator with a new one, and guess what ... the error message returned today.

I have checked the system with an iCarsoft error unit and there are no error codes listed. The voltage is showing 12.6 when the engine is not running and 14.2 when the engine is running. The SBHC (brake hold) facility is sometimes "Not Available" but not always. The SBC pump was replaced in 2013 and has not given any other issues at all.

Anyone know if a fault in the battery control module in the boot can occur without reporting a system error code? An other ideas?

Thanks

 

[Botus]

they also have a silly aux "motorbike" battery beside / under the windscreen washer bottle... if you've never done the pollen filter that sits on top of the blower motor and or lifted that silly flimsy cover by the bulkhead you've probably never seen it

its designed to provide the effect of a conventional brake servo for the shitty SBC brakes in an emmergency

they last about 5 to 7 years and then need swapping out (its another baby AMG one). merc dealer will have for £100 or you can go tanya batteries and get for much less

 

[grahamwoodward]

Botus: Aux battery was replaced 6 years ago. How do you tell if it's the problem?

 

[AMGeed]

Botus: Aux battery was replaced 6 years ago. How do you tell if it's the problem?

Put a multi meter on it to check the voltage.
At 6 yrs old it is probably the cause of your error message.

Fiamm is the OEM battery and now costs around £90 from the dealer.
I replaced the aux battery on my E55 just before I sold it with this one.

Mercedes Battery for Auxilliary Pump for Brake System

512 014 020 VARTA Powersports AGM Motorcycle Battery <i>Innovation with Purpose, Premium Experience, Powerful History</i> VARTA was founded in 1887 Germany, and was established fully in 1904 by delivering the first electric vehicle battery, famously driven by Thomas Edison. Soon after, VARTA...

www.tayna.co.uk

 

[grahamwoodward]

AMGeed: Thanks. I'll get it checked on Monday. Thanks again.

 

[Mark A]

I thought red was the main battery and white was the Auxiliary one.

 

[Botus]

Botus: Aux battery was replaced 6 years ago. How do you tell if it's the problem?

that's the one that puts the red light on the dash - because its safety critical,
pretty sure on my autel kit it tells you in the error detail that red the battery message is for the brakes