I have the message "Auxiliary Battery Malfunction" displayed.

Does this mean the auxiliary batter is bad? There is no "visit workshop" displayed. Also, it went away after being displayed once.

If it is going bad, is this battery located behind the main battery so everything has to come out again?

Thanks.

 

Yes, it is next to the main Battery. Make sure the Aux. Batt. is fully charges before installation. And follow instructions to a T.

 

Is this a difficult installation? I mean how do you make sure that you don't fry the electronics?

I don't have a charger for such a battery - so this means I cannot install it myself?

Thanks!

 

Thanks for the pdfs. They are great.

What's the best place to buy an auxiliary battery? Amazon has almost 2 weeks delivery time.

 

Do you at least have a volt meter?

 

I just checked Amazon and they have 3 in stock. Order now to get one.

The Aux. Battery has only one use and that is if your main battery is faulty you will be able to put it into NEUTRAL so your veh. can be towed.

 

Thanks. I read about it powering electronics but it looks like it should be called a backup battery and people on the web warn to drive with the auxiliary battery malfunction sign on.

Actually, I drove for an hour today and the warning didn't come on. So it's likely on the brink.

My main battery is only six months old. Shop should have exchanged the auxiliary as well.

I don't have a voltmeter, either. So it looks like I shouldn't be doing this thing myself.

 

Invest in this tool. Plug it into the front 12v socket and it will tell you what is the battery voltage while the eng. is off and eng. running.

 

Thanks for the tool tip.

If I plug it in I will see the main battery's voltage, not the auxiliary battery's, yes?

 

The aux battery is essentially an Uninterruptable Power Supply (UPS) battery, AGP type (fiberglass-matt in the electrolyte).
If you've a second vehicle and have a nearby store like Batteries+ (really any battery specialist store) - you can pull the battery and take it in for a match.
(Assuming you haven't already ordered one online)

I replaced mine with a Duracell UPS battery with the same capacity and physical size, it works fine. Cost me about $25-30.
There's absolutely no reason to by Mercedes-branded battery for this.

 

That is correct.