Drained Battery

[littlewimp]

Since owning my S500 I have experienced an almost completely flat battery Twice. its been fine for the last 10 months but this morning Dead again, I know that the s class has a lot of electrical equipment fitted so was wandering if anyone can give me some advise on were to start the diagnosis. Regards Neil

 

[television]

Is the car a 220 or 221 please.

 

[littlewimp]

s 500 w220

The car is a 220 . Thanks Neil.

 

[littlewimp]

Does anyone have any thoughts on my problem or would anything show up on a diagnostic machine? Thanks Neil

 

[television]

You could have a drain check done, that is an ammeter is series with the battery or better still using a clamp meter, what you need to know is the standing current that should be in the order of 55ma.


Things like a boot lamp staying on, the heater box full of water can all cause drains, more complicated is when the car is not going to sleep.

 

[littlewimp]

Thanks Malcolm, There's a good chance that it could be connected to all of this dreadful rain that we have had over the last week, would there be an easy way of checking the heater box for water ingress and is there a reason for it getting in there in the first place.

 

[television]

The heater box needs air, but water also goes in the air intake and there is a drain pipe in the box. I am not sure where this drain pipe comes out, it could be in the rear section of the front wheel arch liner near side.

The pipe is 530, if you look in the air intake in the top rear of the bonnet you may see water, if there is some, you can on the 230 see the bottom of the box

 

[littlewimp]

Just had a quick look into the heater I can see the drain pipe in the bottom which looks clear enough and although its pretty wet in there the waters not hanging in the bottom, I will try a clamp meter and measure the power drop later and go from there. Neil.

 

[robertjrt]

Since owning my S500 I have experienced an almost completely flat battery Twice. its been fine for the last 10 months but this morning Dead again, I know that the s class has a lot of electrical equipment fitted so was wandering if anyone can give me some advise on were to start the diagnosis. Regards Neil

This is what happened to my car, it was a drain from the front passenger seat electrical unit, evidently!

I would suggest you have a 'dead short' somewhere and until you find it the battery will be constantly drained.

 

[bembo449]

on mine , the seats and steering wheel electric wernt going to sleep

 

[littlewimp]

Ok Thanks, so is it the case that if I can find certain functions that are still active once the keys have been removed and left idle for a while then that could be connected to the problem. it just seems strange that it been fine for the last ten months or so.

 

[bembo449]

yes you will pal

 

[littlewimp]

Was sat in the car earlier and everything appeared to be shutting down like it should but not all at once, I think the last things were the fan behind the heater vents in the dash and the illumination on the stereo on/off knob, I then operated the boot and noticed that the red close button seemed to be flickering so I'm thinking that maybe the driving rain that we are having has got its way into something electrical causing me a problem? the boot did however close on this button as normal.

 

[television]

The weather is not good at all for many cars.

 

[SL63 Mark]

The weather is not good at all for many cars.

You should try cycling Malcolm, that's even worse, mud, trees down, floods, debris everywhere, and enough wind to blow you across the road.

 

[littlewimp]

Tonight I connected my meter in line and had an initial reading of 5 amps drain and after about I minute this dropped down to 0.1 of an amp, I am now doubting the battery although its quite a new bosch one so I have put the one of my Porsche on and will check the voltage on that tomorrow night.

 

[littlewimp]

Well that's my theory of the battery out the window, the worst thing seems to be that its not draining the battery at all times. I left it for three days and it started without an issue, this morning I started it before going to work and trying it tonight when I returned home it didn't have enough power in the battery to even open the doors so that's a major drain . what would you recommend I try next except for the petrol and matches.

 

[television]

You have to wait up to ½ hour for the car to be asleep, early comands can stay awake for 25 mins.

 

[littlewimp]

I'm just waiting for a new meter to arrive that I can connect in-line with some long leads then I can closely monitor things over several hours to see exactly what's going on.

 

[television]

It will help if you do not use the comand on days when you want to check, they can stay awake for ages.