cholley

2010 MB 350E suddenly shows Aux.Batt. Malf. in speedomenter unit. I checked hoses,OK checked belts,OK, checked TEMP OKIs it a problem to drive to get checked and fixed, what could have happened?

KEY08

So you need to replace your auxiliary battery, which for your 2010 is under your dash. Search here for "auxiliary Battery warning" to find out how. There is no danger in driving wherever you need to go.

Bigbrotherhd

I have a 2014 E350 Mercedes-Benz with 39,000 miles on it auxiliary malfunction came on about 30,000 miles today I decided to check the battery in the trunk. I removed the two terminals making sure they don't touch metal I checked all the fuses which were all okay I turn the car on with the battery disconnected it still says auxiliary battery malfunction I put the battery back on shut the car off make sure the terminals on the battery was tight started the car now auxiliary battery malfunction warning is gone and my my Eco light came back on. I think the issue was the terminals get loose after a while I did a voltage test on the battery while it's disconnected and it was reading 13.9 volts which is pretty good.

ItalianJoe1

It checks internal resistance of the battery, it will fail again soon. Every one we replace under warranty has plenty of voltage, I've tried out of my own curiosity to clean the terminals and re-tighten, clear the codes, and it comes back usually on the next drive cycle.

Just replace it, it's not an expensive battery or difficult to replace. The S class one is slightly more inconvenient to change but is the same physical battery.

walmck

I replaced mine with this:https://www.ebay.co.uk/itm/Genuine-L...53.m2749.l2649
Had no issues, i even swapped the sticker with the MB part number on, so it looks the same, only difference is you don't need to connect the clear air tube on the side as this one is a gel battery.