So I parked my W205 about 16 months ago. Problems with "Adult onset Epilepsy" and I didn't even get to have all the fun doing the drugs to get it like a normal adult. Should have sold it but then trump was elected and I don't have a problem holding onto it as it is paid for and still a cool car.

So kept it near empty, ran it every 3-4 months for 30 min, threw in a bit of gas, did some stabilizer and had it out for a quick rip just to keep everything lubed up.

It almost always needs a boost. Over the last 6 months it got more difficult to start. Even with cables it wouldn't even really try to turn over. Just one partial crank maybe 2 then dead.

Over the weekend I tried again, nice warm weather (For Canada in the winter). No dice, kept it on the cables for awhile. Still the partial attempt to even turn over. After a few tries nothing (Interior was getting power from the cables).

Current state: Will not crank, seems to be fried without cables. So naturally I get a fresh battery to try, which I have not done yet because with cables it should still try to crank unless the battery is completely bricked. Door number 2: In the blurr of power related errors is the Aux Battery Malfunction (Been happening a bit before parked) which I understand can cause this?

Before I go to door #3 which is the starter has anyone else found replacing the aux battery to fix it?

 

Your DX of hte vehicle is about as off base as your DX of adult onset Eliepsy, well, unless your car is currently detoxing and having Gran mal.

In both instances the culprit is going to be the brains, more so - damage to the brain (infrequently from drug abuse as compared to alcohol consumption). Most frequently as a secondary condition to tramatic injury (concussion) and in your case...I would DX that as a CAN issue more than a battery issue. The car simply does not need the Aux battery to start and run. It needs it from some ancillary functions such as cruise control, brake hold (I do not think C offers that). You need to get a scanner and EKG the car to see where the electrical connections are crossing...99% rear CAN.

 

Ouch to a lot of that. I don't usually run into epilepsy academics on the car forums haha. Justified I suppose.

Rear CAN bus also controls the camera I assume then? Also stopped working just before I parked it. I have a scan tool (Requirement for owning VW/Audi).

Yes, no brake hold. My Passat CC had it but made sense because it was 6 speed.

I'll run the scan. I am not familiar with MB codes but can it be something as fundamentally simple as a short? I would have thought the battery ground would have had to be bad to cause a large problem like this on that front.

 

In general it will show up by NOT showing up. When the CAN in my C went out it was simply things missing. When my CAN went out in one of my E's it was the same. Seeminly unconnected items non-functional. There are many threads about the CAN in C and E (and other) cars.

 

If you're just running a run of the mill OBD2 scan, it's unlikely you'll find anything useful. You need something like a Creader x431 specifically for MB to pull the CAN diagnostics related to all the modules in the rear.

 

Thanks for the insight gentlemen. All relevant thoughts surrounding the simple solution. It was a bricked battery. Scanning with a basic OBD tool did only reveal what didn't want to work which included the rear camera before it was parked.

I am not a fan of just letting it idle for awhile (as it is usually detrimental to the charge shorter than 30min+) but taking it for a quick rip around the neighborhood to clean the brakes a bit then let it sit for an hour and warm up/dry out.

Edit* Guess you can't really see the exhaust cloud. Waste of time.

 

My wife drives the GLS from home to the clinic and back...all in all, about 2/3mi a day. After a bit the batteries are low and I need to charge them. Takes so much to start the car that it does not charge back up by the time she is there. Got to love modern vehicles.

 

Before you even turn the key to the on position after you open the door you can hear it moving vents around or something of the like.