Help, car is losing charge!??

[airportstar]

I drive my car everyday for work.

This morning I went to unlock my car.... nothing happened. Car totally dead. Opened car manually with key, nothing worked.

Battery is no more than 1 year old.

Rac man came out, attached the plug to my car battery and the car started striaght away.

Rac man said battery has tested ok.

But is losing charge of about 1.7 (reading from the little yellow device he was using), he said this was very high. Average reading should be around 0.5. This reading was the same for 20 minutes, with everything off.

At this rate Rac man recons it will lose charge in a couple of hours.

Anyone have any ideas please!

Simon

 

[npuk]

Check for the usual things like boot light or any interior lights staying on. Someone previously had an issue with Comand causing battery drain so if you Comand try removing the fuse for it and use a multi meter to see if that stops the battery drain.

 

[bennesspipers]

I seem to remember if the diode in your alternator goes it can cause battery drain.

 

[airportstar]

I seem to remember if the diode in your alternator goes it can cause battery drain.

Sorry, Im not very technical, if the diode goes will the alternator still work? and how much am I looking at.

One hour after the Rac man has left, battery completely dead again. Remote locking doesnt even work!

 

[allias]

If it was reading 1.7 amp that mean you got to look for reciver that takes about ~20-22W. That could be 4 5W bulbs or radio on quite low volume. I would say check around for anything that could possibly stay on while key off.
Check for thing that hard to notice straight away like boot lid light or glove box light. Look for switch and if its stuck what couse drainage.

Try simple things first before you spend more for electrician

 

[pmcgsmurf]

Isn't there a little module in the boot that stores information on what is drawing current?

A visit to a dealer with STAR should quickly be able to diagnose this.

 

[airportstar]

Everything seems to be switched off! In my w211 E320 cdi taking the key out of ignition switches everything off right?

Any mobile merc specailists or auto electrician in the London Docklands area you can recommend???

Or do I need to make the long trip down to Ollys again?

 

[BlackC55]

Isn't there a little module in the boot that stores information on what is drawing current?

A visit to a dealer with STAR should quickly be able to diagnose this.

Not true. It has a battery control unit but this does not store such information. No control unit does.

 

[Tiff]

Easy way to check things out if you have a little time. Disconnect the earth terminal from the battery. Connect a test lamp between the earth terminal of the battery. If the light glows brightly,then it proves you have a drain. You will -or should get a very dim light due to clock or alarm drawing a small current. Pull the fuses out one at a time and see which one causes the test lamp to go out- this is the circuit that is draining the battery- it will point you in the right direction of what is causing the problem.

 

[BlackC55]

Look for anything lit up. It is best to check this when its very dark. Lock the car and after 20 mins have a look inside.

Common ones are the instrument cluster, command, door modules, ignition switches and sam units. etc

 

[airportstar]

Olly, what do you think is the likely cause of the problem?

 

[BlackC55]

You need a drain of 0.06A or less.

 

[BlackC55]

Olly, what do you think is the likely cause of the problem?

In reality it could be ANYthing electrical. See post above.

 

[npuk]

Any mobile merc specailists or auto electrician in the London Docklands area you can recommend???

Forum meber Willow132 is a mobile merc specialist and is london based.

http://www.mbclub.co.uk/forums/members/willow132.html

 

[pmcgsmurf]

Not true. It has a battery control unit but this does not store such information. No control unit does.

Thanks.

I remember the dealer telling me they could tell what had been left on if you called them out to a flat battery so assumed some information was stored.

 

[Stratman]

Does your car have memory seats? The control modules have been known to fail 'on', drawing about one and a half amps.

 

[misfire84]

I have a similar problem 0.85A pulled fuses , unpluged seat modules, interior light , boot light radio takes 0.25A thats it still 0.55A draw ? just sticking a trickle charger on over night ........

 

[airportstar]

Andy @ Merc Tech has been looking at my car.

Looks like the battery is to blame. When my last battery died, I fiited a non MB battery. Andy believes it needs to be a MB gel based battery and the water based generic batteries are no good for the Merc.

 

[bennesspipers]

^interesting, not heard that one before. Has anyone else heard that ?