mnsharif

Hi, this is my first time posting on this site, I hope I'm in the right forum.

I have a Mercedes E350 2011 4 matic.

Most of the time, my car starts normally, however, occasionally, we need to boost it with another car battery. It's very sporadically happening, and enough for me to think there's a problem.

We have checked the battery and it appears to be working well. And also, when I exit my car, I make sure everything is off. I was on vacation for two weeks and came to start the car, and there was no problem starting the car.

Therefore, I thought that if it had been sitting there for so long and was able to start, it couldn't have been a battery problem. But then, two days later, we had to boost it. I'm thinking it might be something electronic maybe. I still feel there is something electronic that is running the battery occasionally in the background, and I don't know.

Any help or suggestions?

PeterUbers

It could still be the battery... Put a voltmeter to it and see what it's resting voltage is ... When did u last change the battery?

Live Oak

Check out the "bulletins" and "service" sticky threads.

There are some service bulletins and service notices re: battery problems, specifically regarding a fan running too long, etc.

homeofstone

Make sure trunk is closed completely or light may say on.

Arrie

There has also been posts about the starter motor being bad causing intermittent starting problems.

dbldpr

would change the battery. Even if it looks ok it is 4 years old and that is long enough on a battery. If it still does it at least you went with the cheapest part first.

Alex.currie44

I haven't checked my W212 for this but my W211 had two batteries. On starts the engine. I believe the W212 does as well. The other runs all the other stuff.
You need to check to see if you have two batteries before you do anything.

Louisaet7

Hi fellow E350 owner. Did you find out why your car is not starting?

Alex.currie44

I checked with my dealer and he tells me there is only one battery in the W212.

sghokie

Mine has 1 in the front but in the trunk looks like there is a cavity for one, but no battery.

Alex.currie44

Without seeing it is it space for the sub woofer on the H-K sound system?

Louisaet7

Thank you for replying!

ddeliber

I believe all W212s have 2 batteries BUT the second is not what you think. The second is called an auxiliary battery and it is only used to partially power the console to enable shifting the car into neutral (electric gear shifter) in case the car won't start and it needs to be towed. The only reason I know this is because I got a warning light saying Aux bat low and I asked about it when it was replaced under warranty. Now is it possible that my SA was full of it or didn't know the real truth, sure, but this is the story that he gave me.

BeachBunny

OP has a 2011, so there are indeed two batteries, the main battery and the auxiliary battery for the transmission.

For 2014+ W212, there are 3 batteries: 1) Main battery, 2) Auxiliary (transmission) battery, 3) ECO Start/Stop battery which powers the electronics when the engine's off.

jhodies

Can the OP (mnsharif) give us an update? I have the same exact problem with my car. I went ahead and ordered an oem battery, scheduled for install next week. I'm hoping that's all there is to it.

noka

Actually, I think OP has a vintage E-class from "1911"

I only knew about two batteries (under hood: I believe for starting and with posts for jump-starting, in trunk: I thought for ECO to power accessories when engine is off). Where is the third battery? Anyone know the precise function of each, in case I was mistaken?

konigstiger

1.2AH battery is backup for transmission electronic gear selector apparently sometime during production run MB removed this battery, best way to confirm if vehicle is equipped with said battery is to run VIN.

noka

I didn't find any info in the owner's manual. Is there any doc about how it is accessed, what type of battery and if user replaceable?