W211 Parasitic Battery Drain Problem

[walshy66]

Before the problem , let me wish all a Happy New Year.

I've read a few relative posts but wondered if anyone could shed new light.
I replaced the battery on my 2003 270 CDi yesterday for the 3rd time in 6 years. No drama in that , as the last 2 were covered under a 4 year battery guarantee, so I've only paid for the original replacement battery soon after i got the car in July 2015. All 3 have been 90aH Platinum, fitted July 2015, Jan 2018, Dec 2020
Decided to do a little testing and found I'm getting a 0.3A drain (tested with a Fluke meter in series with the Neg lead/terminal) with the car stopped, and all doors/boot/bonnet closed and locked.
As things were closing down the current from 2.5A dropped steadily bit my bit to 0.3A (297mA to be accurate), but after 5 minutes it remained at that.
I'm an electrician so I have a decent understanding of isolating circuits to trace drains etc, but I'm unsure of the following:
*Location of all fuse boxes
*Any known common faulty components/circuits causing battery drain on W211's
*Consequences of random disconnections
*What is the expected standby current when a W211 goes to sleep
*How long before all the systems do actually go to sleep

Sorry for so many questions , but I'd like to get to the bottom of the problem , so your help would me most welcome please
PS. The car has a MB Viseeo phone unit in the centre arm rest, and the only known problem with the car is the 6 disc CD changer has never read discs/been recognised by the stereo, although the motorised cover plate works fine, opens and closes as expected. May be irrelevant but thought I'd mention these just in case.

 

[AMGeed]

Current drain does seem to be a recurring problem with 211's. My previous E55 had one that I never got the bottom of.
Apparently, up to 65mA is acceptable. Anything above, as your is, needs investigation.

The Comand unit, the door and seat controllers are three known points for an abnormal current drain.
I'd start by removing the Comand fuse and seeing if that is the culprit.
There are 3 main places for the fuses. Engine compartment drivers side by the bulkhead. End of the dashboard, drivers side. In the spare wheel well next to the main battery.

I have the fuse diagrams for a W211 E55 (211.076) which may be of help. I can photograph any pages and post them if you want them.
Disconnecting the main battery shouldn't have any consequences apart from maybe having to reset the window and sunroof. You probably know neg terminal off first and reconnected last.

If you are going to test each fuse for a current drain, I was informed to wait for 20 minutes after locking the car.

 

[MJJ]

I have been through this fairly recently with my S211, perhaps the attached thread can help - Link here . This includes a graph of expected current consumption from Mercedes workshop online manual - WIS, which should help with your last two questions.

For the others, the alarm siren (my problem), Command system and any genuine Mercedes iPod kit seem to be the most common causes of drain. I am not aware of any issues with random disconnection, all you should have to do is a quick, manual reset of the one touch windows.

On my '09 estate, there are three fuseboxes, one in the nearside boot lining, one in the engine bay, and one on the offside end of the dashboard (driver's door needs to be open to access this one). I would start with the boot one.

Martin.