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2002 LWB LHD G400 CDI
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Discussion Starter #1
Hi,

About a month ago my battery died (after few times it drained to zero) and I bought a brand new Varta battery.
Since then its the 4th time the battery drain to zero over-night or over 48 hours.
I dont get it as sometimes it last OK and sometimes drain overnight..

I dont have any accesory which is not genuine (at least not that I know of), like hands-free kit, DVD or else.
I do hear the Command system's fan keep running sometimes after I turn the key off.

Do you know of this issue or the cause of it?
I guess the systems on the car do use electricity while the car is off so I dont know how can I trace a leak if any...

Thx
 

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2001 G400CDI
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You should use an ampermeter in series with your battery and check the current when the car sits for a few minutes (after all electronics shut off). Then you can test which fuses are still in use and unplug them one by one observing if the amp reading drops within normal values (usually < 100mA). In max 30min you should be able to pinpoint the circuit.

PS: In my case someone messed with the bolts in the center console and put long ones instead of short which lead to tv tuner wire harness being punctured and shorted.
 

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2002 LWB LHD G400 CDI
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Discussion Starter #3
Hi,
First, I replaced the battery with a brand new one (has a nice sticker on with saying "Power Frame", seems like an improved version of the Silver line).

The Volt meter reads 13.7-13.8 when the engine is running with A/C at full power.

I turned off the engine, took the key off and waited 15 minutes, then read the current on each fuse (used a blown fuse and Amper meter).

All fuses read 0 but 2, fuse 21 and 24 which read 70-100mA each.

I am not sure how low the battery can go and still be able to start the engine, but assuming there is a 150mA drain, it should drain 20% of the baterry in about 5 days..
 

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2000 G500 NMLE
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Hi,
First, I replaced the battery with a brand new one (has a nice sticker on with saying "Power Frame", seems like an improved version of the Silver line).

The Volt meter reads 13.7-13.8 when the engine is running with A/C at full power.
If you're only getting 13.7-13.8 volts with the engine running, methinks you have a bad alternator or voltage regulator on the alternator. It should be more like 14.4 volts.

That still doesn't solve the current drain problem, but it might be related.
 

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2002 LWB LHD G400 CDI
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Discussion Starter #5
thx Dutch, I was pretty sure the anything 13.8-14.2 is ok.
is it possible to replace the voltage regultor without taking the alternator out?

also, now that I am thinking about it, sometimes I hear a short squeal when I turn the engine off, but I though it just a load on the altentaor during turn-off..
can it be a sign?
 

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2001 G400CDI
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Usually with 40% capacity should be no problem starting, but the amps you mention are not accountable for drain alone. It could be something else. You measured amps with each circuit with the blown fuse, but what I did is hook the ampermetre right at the battery terminals, than I closed all doors, windows while still inside and locked/armed the alarm. Then waited until all fans and IC turned off (cca 1min) and read the amps. Then I started unplugging fuses.

This should give you a better all-around amp drain.
 

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Hi,

The Volt meter reads 13.7-13.8 when the engine is running with A/C at full power.
Don't worry about the voltages, they look fine to me. Anyway they should be measured with all electric stuff off, engine rpm around 2500-3000 for a few seconds than read the value, and then the same over again with headlights on, etc (by the book procedure if I remember correctly). And also they are precalibrated for AGM-type batteries which usually require slightly less voltage.
 

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2002 LWB LHD G400 CDI
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Discussion Starter #8
thx, I will try the AMP test and the charging test today as you suggested.
 

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Discussion Starter #9
ok, the volt meter read 13.8V at all times and RPMs.
will do the AMP test later as I like the weather to be nicer for me to sit in the car with no A/C :)
 

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I had a similar problem with my battery and it turned out that the module that moves the seats was faulty. Try disconnecting the module (under the seat right side) and see if your battery continues to drain.
 

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Discussion Starter #11
Hi,
Took me a while but I made some progress..
When metering the current in serial connection - I get 1 !! Amper (Current and steady).
I disconnected the seats modules - no change.

I then pass on each fuse (on the left side of the dash board and under the glove box) and no one is affecting the drain.

tomorrow I will continue with the fuses under the arm rest (btw, how should I get it??)

if you have any other idea I will be glad to hear.

thx
 

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2001 G400CDI
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Yeah, I have one ideea: unplug the tv tuner above cd changer.
To get to the fuses below armrest move the seat forward, rotate the plastic clips 90 degrees left and remove the panel. then position the seat as you see fit. You will probably get to the tv tuner fuse which causes the trouble (happened to me too).
 

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Discussion Starter #13
thx
you mean the right seat?
and should I disconnect the tuner itself as well?
 

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thx
you mean the right seat?
and should I disconnect the tuner itself as well?
yes, the right seat for the fuses. if it turns out that the tv tuner fuse clears the drain, then u need to unplug the tv tuner.
Or, you might just want to try to unplug directly the tv tuner (takes 2min) and read the amps.
 

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Discussion Starter #15
thx
I remember there are few looms connected to the Command multimedia console.
which one is the tuner?

thx
 

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2001 G400CDI
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Oh, I meant to unplug the tv tuner in the back of the car. It has a 2wire 12Volt plug. that one needs to be removed.

Unscrew the two bolts of the cd changer , take off the mask, and then remove the carpet. then unscrew the metal lid and voila the tuner. unplug the 2 wire thinghy.
 

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Discussion Starter #18
ikeakayke - you are my hero (once again) :)

I couldn't wait till morning so I took a flashlight and went to check it.
I disconnected the 12v connector from the tuner (above the CD changer) and its now reads 120mA (alarm not armed).

If its MB fault the tuner is buggy they should at least send us vouchers for a new Command system, right?

anyhow, I think 120mA is OK and should allow the battery to hold 3-4 days easily, correct?

Thx alot
G

BTW, can we lowwer the 120mA more? what is is using for if the alarm is off?
 

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At this amperage 0,120 the drain is ~3A / day. The battery, if in good condition has ~100A. So the math says you should be able to start the engine after at least 20 days (which should give you ~40% capacity left).
Anyway I think that after some time the current drain will drop around 70-80mA which is the norm in justifying the alarm and other systems standby.

As to the tv tuner, it is not it that is faulty, is something else. I bought another one from ebay and it's the same thing. The weird thing is the tuner stays ON by default until something gives it the command to enter standby. I only gave it one day of trobleshooting and then I gave up the only thing discovered being some wire harness punctured in the central console due to long bolt instead of short one. These wires lead from tv tuner to command back end. But then again who needs a tv tuner right? :)
 

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Discussion Starter #20
:) I will know if the math is working in few days..

thx for the help, I easily gave up on the TV tuner.
 
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