I seem to have an issue with my battery draining if i leave my car for 2 days, it is drained absolutely flat and its a pig to get to the battery in the boot! anyone have similar issues. Obviously i have replaced battery and checked there is nothing left on i can see overnight!

 

S Class like many other MB's have software to turn off the battery in the event that something is left on. e.g. Boot / interior light etc.

If you are getting a flat battery I suspect that you have a faulty battery despite the fact that you say you have changed it.
I suspect that the battery may not have been CHANGED but possibly CHARGED. Once a battery goes flat (below 12.5 volts) it is SCRAP!

Alternatively you may have a faulty alternator which has caused the new battery to fail in the same way as the previous one did.

A new battery does not go flat if the vehicle (S Class) is left for two days.....UNLESS the Body Electrical Controller has gone bad. If so that will cost BUT they are extremely reliable.

Stuart

 

Not sure if you have the same problem, but I suffered the same symptoms and it turned out to be the ignition switch. After the ignition was switched off a device somewhere was remaining online. If I listened carefully I could hear static coming from the speakers. It was curious in that changing the volume or powering the radio on/off had no effect on the static. This did not happen every time the ignition was switched off.

 

I have a 2002 c230k with the same problem. I have pulled the fuses and still drains the battery. I have confirmed it is not the alternator. But I suspect it could be the ignition switch. I put a dc amp meter on it and found the drain to be .8 amp pulled the fuses and down to .5 amp. This will still kill the battery in 2 days. This could be very well be the switch. Any comments..anyone?

 

I had the same problem, but I knew what caused it, I tried to charge my battery after not driving it for a while, it was in the earlymorning and I mixed up plus with minus for a split second, so I took my alternator out and took it to the shop, they tested it and it was burned regulator, they wanted 170$for therepair, I went on ebay and bought exactly the same stock one for 15$ and changed it myself.

 

I have a 2000 S430 that drains the battery after few hours. If I disconnect the battery, I can restart the the car. This tells me that the alternator is OK, but something drains the battery. If anyone has any idea, please post. I did not have this problem until I took the car to the dealer for some diagonstic. The dealer declines to accept any resoponsibility, but I am not goint to pay them again to find the problem which they put in. Thanks in advance for any help.

 

Hi Andy,

Now this is VERY interesting!

I understand the electrics on this vehicle reasonably well and I too have had exactly the same issue with my local dealer.

My vehicle has run with no difficulties up to 120+k miles and has always started after even three weeks in my garage.

Since I do all service / preventative maintenance work on the car myself it never goes near the dealer. However a recent intermittent fault on the Airmatic was causing me difficulty and I asked my dealer to do a Quick Test on the Airmatic (and other systems).

They did the test but were so intrigued by the results they they attempted to locat the problem which turned out to be an intermittent break in the airmatic pump sensor wire inside the wiring harness leading to the pump. The wire had a "nick" in the insulation of the wire WITHIN the harness and salt water over the years had caused the copper conductor to corrode causing an intermittent signal which allowed the car to OCCASIONALLY remain in suspension rising condition but without the car rising.

They spent about 5 hours finding this and in the end only charged me £150 which I actually paid quite cheerfully because without the airmatic code info I was unable to find the problem myself. Interestingly the code reported a PUMP failure (since the pressure sensor is part of the pump) but in the end they agreed with me that the pump and pressure sensor were OK!!

Not sure how significant this is but they also said that they had had all sorts of problems with the EIS Electronic Ignition Switch and that assorted menu items weren't available that should have been etc.

Anyway, all appeared OK until till dusk on the day I got the car back when I got a RH Tail bulb warning when the lights AUTO came on as programmed. The bulbs were working fine so I didn't worry about this unduly.
2 days after the car wouldn't crank and the battery appeared flat. I turned on the headlamps and got a "Turn Off Headlamps" warning as part of the consumer load shedding process. Away from home I fit a new battery and all appears OK till a further two days later and I get a repeat no crank. Obviously it was unlikely the battery and after checking battery voltage a little low at 13v (should be lets say 13.2 / 13.4v but certainly not dead).

I disconnected the battery and reset the ECU's (basically power off) and all was then OK. I also checked the quiescent drain. The onboard computers shut down in sequence exactly as they should and after about 2 min the quiescent was down to 50mA.

At this point I looked at the Quick Test results that the dealer had done for me and what do you think?
The voltage was reported as 10.1 v!! plus a whole host of low voltage and other faults including about 10 on the rear SAM (bulb warning faults).

I tackled the garage over this...the car wouldn't have started etc so the result MUST have been in error and the dealer undertook to look at the car again (strict instructions Free of Charge") and after two days (I was in no rush) I got the car back.
I was advised....."We have looked at the car and you will now find it OK Sir!"

I asked what had been found and they were very coy. I pushed more but got no answer. I've now run the car for a further week and several thousand mile and all is OK again.

So what caused the problem and what did they do when they had the car back?

Maybe I will tackle them again now I have regained my confidence and am even more convinced that the dealer did something.

Shooting from the hip I suspect that they disconnected the battery with the key in the ignition (whilst repairing the Airmatic) and the strange subsequent Quick Test results were due to the ECU's not being reset afterwards since the problems all appeared to go away after I had reset the ECU's.

Sorry for the long and maybe not entirely relevant response BUT I suspect that the dealers do / can intro problems exactly as you suggest.

Stuart

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