samazam

Hi,
I have S500 where battery is getting fully drained in two days and upon troubleshooting with AMP meter i narrow down the issue and found that with Fuse 78 plug in AMP drawn are in the range of .2 to .4 Amps however; when i unplug Fuse 78 AMP reduced down to .05 or 0.06 AMPs which should be desired AMP drawn in the resting state.

Any idea to move forward from this point to on ward will be highly appreciated. By the way following are all related to Fuse 78:
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Adjustable steering column;
Anti-theft alarm system;
Cruise control;
Engine management unit;
Ignition lock;
Steering wheel heating;
Steering column module;
Windscreen wipers

If someone can help in providing the wiring digram then it will be very helpful too.

Regards

tusabes

Fuse 78 controls the alarm siren, which is responsible for a lot of battery drain issues, as it contains nonreplaceable lithium batteries, which have finally degraded at this age the alarm siren is located under the left front wheel well liner You can either replace it with a new siren or just disconnect it.
https://www.benzworld.org/threads/he...ation.3044517/

samazam

Thanks tusabes;
it worked; AMP with faulty Siren Plugged it was .4 to .6 AMPs and after removing the siren wire it dropped down to .05 Amps which is the desired AMP drawn from a car battery during resting.

Now i would like to give my over all experience and recommendation for batter drain issue:
At first i had tried to un-plug one fuse at a time but it was not making and changes on the AMP meter and out of frustration i un-plugged all fuses from all fuse boxes and then started plugging-in one by one and it was much better experience and it was very simple too.
All those fuses which powered multiple elements are typically the one which make changes on the AMP meter reading and others does not put much difference on the AMP meter reading and once these are plugged AMP reading goes high but then within a minute or max two it drops down provided none of the element linked to these fuses are faulty. For example; for all fuses other than Fuse#78 AMP reading went hight to 2 to 3 AMPs but then it drops down to 0.06AMP.

So, i think we can significantly save lots of time by starting unplugging all fuses and then plugging them back, i am sure that if i have to find out a fuse linked to high AMP drawn then it can easily be troubleshooted in 1 hour time and dont worry about the W220 it works after you plug all fuses back.

Regards

tusabes

Most people forget which fuse goes where , that’s why conventional strategy is to remove one at a time . There are also some blank spaces not used in some models

if you take a photo for reference of the fuse box before pulling fuses it can make it easier to pull them all out

Fried Chicken

How did you measure amp draw?