Hello to All; I'm a new member and I need help. I have own my C320 Sport for the last 5 years. The first year was rough but not painful since it was under warranty. Recently is a different story.

I would like to start with the discovery this morning that the car was dead, completely dead battery. I have not used the car for three days, but we did open the trunk yesterday and the electric motor in trunk latch worked ok. I got my jumper cables and attempted starting it. I noticed a spark jumped when I connected the last cable of the jumper cables. This gave me the indication that somethingwas shorted or an electrical componentwas drawing juice. Thinking of a shorted battery I disconnected the positve terminal and attempted the hook-up again directly to the car's positive cable bypassing the positive pole of the battery. Same result, got a spark again. Could it be the alternator is shorted out? When I leave the jumper cables connected I still don't have power to the electronic key since it will not disengage the steering locking mechanism. No lights, clicks, or nothing. Dead!

Could it be big brother punishing me for running the car with the check engine lighton for the last 6 months. I had it check by an independent mechanic and he told me it could be one or more of the 4 air sensors. The car was starting ok but with a very rough idle which remain for maybe 15 minutes and would go away after the engine has warmed up good. I thought thespark plugs needed replacement. Could air sensors cause this, and where are these 4 sensors?

Since the check engine light it's been on for the last 6 months that can wait. I need help getting it started so I can get it to a mechanic so I can fix the air sensors, and the shocks, and front disc brakes, and the strange noises the A/C makes when it's turned on, and on and on.

Luckly, I don't drive this car, it's my wife, I drive a big pick-up truck like the ones that will drive over a C320. But guess what; she needs wheels and I need to fix her car now. I hope I didn't upset any MB lover I like the car too.

 

Hi,

Seems like your car is well over due for some TLC!

The Check Engine Light ON is telling you that something is wrong. The first step is to get the codes read. This will narrow down what is wrong.
How many miles, when last serviced, when plugs changed, why did guy say you needed new sensoors etc. Need lots more data to make any worthwhile reply.

So why is the battery dead?

How old is the battery for a start. 4 years old and it is likely a matter of old age. Modern batteries go from OK to totally dead overnight. usually caused by sediment in the battery shorting the plates.

However you mention a spark. Sure you had the leads the correct way around?
Was the key OUT OF the ignition?. Were all services (i.e. Headlights) OFF including doors shut etc?
How big was the spark? A small one OK but a bigger one suggests something wrong.
Although I follow your logic it is not good practice to jump direct with the vehicle battery basically disconnected. This can send transient voltage spikes down the wires and blow ECU's etc.

Now I have no idea what sort of charger you were using but the key is what sort of current was being drawn when you connected the leads.

If the car has not been "messed with" and this is an out of the blue experience I suggest the spark was just a "normal" connection spark since several amps will be drawn to start the recharge process and power whatever consumers remain on e.e.g. Interior light, boot light, doors part way thru lock/unlock etc.
However i cannot be sure that there isn't a direct short somewhere without some more indication of what current is being drawn.

Suggest you remove the battery, take it to an appropriate battery shop and request a health check and recharge / replace as necessary. I would go more than one place in order to get a cross check diagnosis of battery health...after all they want to sell you a new battery!

With a good battery available refit but take care when refitting incase for some reason there is a serious short somewhere...but why should there be??

Sorry i haven't offered much real help but your information is a bit too general in order to give a definitive answer.

The CEL being ON is VERY UNLIKELY to be the cause of the flat battery problem other than if starting has been a problem you have been placing a heavy load on the battery at every start and this may have tipped it over the edge.

Stuart

 

Hello Stuart; Iagree 100% with you on the TLC part. Yesterday evening, after sending the original message, I discovered a couple of things.

I didn't have a charger handy so I gave the battery a 30 minute charge with my pick-up truck. All battery cables disconnected, of course. Afterwards the car started right-up. I took it for a 1/2 hour drive and parked it until this morning, where again started ok. So Iconcluded that the battery and the charging systemare working properly.

Thosecomponents working as they shouldmakes methink that the dead battery was caused by a malfunctioning electrical component. It took over three days to drain the battery, so what ever it is is not drawing that much amperage. The battery was installed new in 2003, the car has 47k miles on it. At the moment when I noticed the sparks on the battery all doors where shut, key was out of the ignition, no lights on, and the cables where properly connected to the battery. Although, the spark was not big it still gave the impression there was something drawing electricity.

I read somewhere in this forum that the dead battery could be caused by bad seat sensors. Anyway, since the car started ok this morning I drove it directly to the mechanic and save on the towing charges.

My instructions to the mechanic where very simple: Give this poor C320 "Tender Loving Care".

I appreciate your response and comments; will let you know how it turns out.

 

Hi again,

the most likely thing to drain the battery are computers that are not going to sleep.

If the key is kept anywhere near to the vehicle this will cause the computers to remain awake and result in a flat battery after several days.

need to check the battery quiescent drain. Should be less than 50 miliamps after 5 mins from locking the car.(or at least something similar)

Stuart

 

Hello Stuart:

Thanks for the advice. Normally keys are kept at a good distance from the car when is parked (40'-50'). My mechanic told me he was going to do a drain check. I will let him know what the proper reading should be after locking the car.

Now I have a question for you. My wife ussually doesn't lock the car since is in a garage. With the doors unlocked, would this cause theCPU to stay active?

By the way; I noticed I failed to mentioned the car is a 2001 year model.

Tony

 

Hi,

Unlocked isn't a problem so long as the keys aren't close.

Incidentally, since the battery is 2003 it will now be at end of life. Sudden discharges are often due to a battery cells shorting to ground through the sediment that forms at the bottom of battery. I still recommend that you get the battery checked. It may last a bit longer but I GUESS THIS IS THE FIRST "WARning" that it is about to finally fail.

Sorry about caps.

Stuart.

 

Hello Stuart:

Again, thank you for taking time to answer my concerns. As you stated, the battery is in fact 5 years old. Normal batteries last about three years, this been an original MB battery I guess it has a longer life cicle. Do you think an aftermarket replacement battery will do the trick or should I stick with the probably very expensive MB bat?

I could probably buy 2 good quality batteries for the price of one MB bat. Technically, that would provide me with 6 years of service. And honestly, I don't know if will keep the C320 that long. Not because of the car, but because is what my wife drive and as cars get older they become more unreliable on the road.

Tony

 

After market (including genuine MB) aren't as good as original oparts delivered straight to the manufacturer.

A 4yr vs 3 yr after market battery should be fine. Ensure you get the correct A.hr rating and maybe consider any heavy duty option if you have cold winters.

Some manufacturers are better than others but I will leave that decision with you. I like Bosch / Varta etc but maybe your market has many other cheaper and equally good ones.

Stuart.

 

Hi Tony and Stuart,
I am the original owner of a 2002 C230 coupe with only 37,000km (23,000mi). The car was not driven over the winter and was completely covered by snow for 4 months. I was able to get the beast going this spring and took it for an extended drive to re-charge the original battery but alas after a few 'iffy' starts over a month, the battery finally died completely and would only take a 50% charge with a charger(barely enough to start the car one last time).
The point of this story is simple. I agree with Stuart. Replace the battery and take the worry out of having your wifestranded. Even the computer to keep the clock correct draws some power and eventually all batteries fail.
I chose to have MB install only because the cost wasn't signicantly higher and I didn't have to re-synchronize the windows, roof etc.