pvindu

Hi All,

I have a 2009 C300 4MATIC. Recently (Ever since Winter started) I kind of have one problem with this car. My Battery just died on me. It is OEM installed Battery.

Day-1: Battery died, called Insurance company, got it stared again with Emergency Road side assistance.

Day-3: It again died on me. This time, I used a jumper cable. Drove for 1 hour on a freeway. Came back, everything is back to normal.

In between I kept driving the car every day. Things were back to Normal.

Then came Winter Storm. Car sat in snow for 2 days and there it goes again, the battery is dead. I took it out got it fully recharged in Autozone. Drove 600 miles in 2 days and came back home.

Had to park the car for 36 hours, it started normally. Went to short drive may 3 miles to shopping mall, there battery died again. Jump started went to autozone, this time to test alternator and Battery

They said Alternator is fine, Battery is fine, just it needs to be charged.

My question

when alternator is fine, battery is fine, what is that is drawing battery??

I have a infiniti 2008 G35, which is running awesome on my OEM battery. Whats that is different in MB C-300 to draw so much juice out of battery???


Any assistance is appreciated.

Pete7874

First things first: how old is the car? How old is the battery?

As a side note, you posted this in the wrong forum. Your car is a W204, not W205.

pvindu

2009 C300 4MATIC. Battery is OEM Battery. But if the Battery is the problem, wouldn't it come as problem during DIAG in Autozone? I did it 3 times in three different Autozones, all came back with "Good Battery, need Charging result". I took it out and Completely got it charged.

tonyteetime

My rule of thumb is if the battery is 5 years old or more , then replace it. It's not worth the headache to squeeze more years out of it. The cost of a road side service or a tow could cost as much as a new battery.

pvindu

I can do that. Thanks for replying. What battery would you suggest?

tonyteetime

I have many cars over the years and don't have any particular preference for battery brand . I think there are something like 3 main companies that make car batteries and then they get distributed and re branded. Stick to the major brand and you should be fine. I usually go for the one with good cold crank power and make sure the new battery fit the space, however if you live in hot climate , then the extra money spent fr cold crank power is a waste.

I think older mercedes car need to be resynch and recode after a change of battery but late models mercedes don't (someone correct me if I'm wrong).

So if you want to replace the battery yourself , this video may help you.

http://www.carcarekiosk.com/video/20...eplace_battery

acr2001

There are two reasons this could happen: your battery is no longer maintaining a charge and needs to be replaced - or - there is a problem in one of the cars systems, causing a parasitic draw (assuming alternator is working fine). Odds are on the battery.

I'm speculating, but the tester at Autozone might not be able to get a solid read on a battery of the large capacity that this car uses. Do you know if they actually load tested it? If not, then there test is not useful.

If you don't want to outright replace the battery, you should have it properly load tested. If you want to check for parasitic draw, you would have to pop the hood, take the key out of the ignition, place an multimeter in the circuit between the battery and the vehicle, wait 20-30 min for all the systems in the car to turn off, and then post how many milliamps of draw you are seeing.

If you want to replace the battery, another OEM battery is the best choice in these cars. There are few, if any, aftermarket batteries that are going to properly meet the specifications.

Glyn M Ruck

You need to find the cause of the parasitic draw if the battery is OK. On the W203 & W209 the common causes were the seat modules & the overhead console HVAC sniffer fan not going to sleep. Something on the CANBus is likely not going to sleep.

If you don't want to put it on a Star to diagnose then you are going to have to do it the hard way. Shut down the car & close the doors with trunk & hood open. Wait approx 20 minutes for the CANBus to sleep. Then get hold of a Multimeter & pull the fuses one by one in the front & rear SAM's until you find which circuit is drawing current.

Load test the battery.

Anh1

I guess its time to change to new battery. Its only about 250 so isnt to bad. Hope you will be fine with new battery
My friend has a c300 4matic. 2009 and still running on original battery. She even left it park for 13 months with out starting the car because she worked in another country. All she needed was a jump start, then she drove it for about 1 hour and the battery is still running until now w no problem. Thats amazing.

tiyyara

I had the same thing.
I thought it is the battery, charged it, next day same thing.
Went to autozone, alternator good , battery good.
Took to MB dealer, after the usual, it will cost 150 to diagnose.
I said fine do it. They said, it is the light switch. The automatic on light switch sticks (known cause as per their info).
650 to change it. I agreed to that.
However it still drained. Then they said it is the front fuse box. 500 USD to changed.
OK do it. (what other choice did I have) Then they did it. Still drained. Then they said ECU is bad.
Total bill 4500, however after a couple of back and forths, they contacted MB USA and I paid "only" for the ECU
Hopefully not an ECU issue for you

Glyn M Ruck

Certain items not "going to sleep" has been an issue with Benz cars. Seems like doing the diagnosis yourself would be a good idea. Dealers forever don't disgnose but throw parts at the problem until it goes away.

lsj711

Hey,

Same thing happened with my w204 2010 C300. Thankfully it was still under the warranty. I called roadside assistance to get it re-charged. The next day I called and had my car checked out. They initially said " We would have to charge you $140 dollars of diagnose fee if the battery is tested ok". I had to take the risk and it turned out that my battery was actually draining. So, they changed the battery at no cost.

My advice:

take it to dealer if u r still covered.

Nicholi2007

Are seat modules a known issue across most classes? I've gone through two batteries like they're going out of style.

https://mbworld.org/forums/c-class-w...ml#post6999752

Nicholi2007

UPDATE: it turns out there is a sensor on one of the battery cables. There was an updated part but no recall. That finally solved it.