CharlyS350

Hi All,

I have 2009: W221 S350. And it battery is also getting drained after I parked it for 2-3days. When I check it shows around 350mA are getting drained even car is in 'sleep'. I have removed the all fuses and check 1 by 1 but problem is still there. Alternator was recently replaced because there was a charging issue and alternator coil was burnt.

After replacing the alternator, I have replaced the Auxiliary battery as well. But the parasitic drain is still there.

I have noticed that rear media amplifier unit is getting hotter even car is in sleep mode. So I have unplugged the cables for it and check but car is still drawing 350mA from the batter when its in sleep.

Please assist.

BulletMagnet

I'm going through the same thing. I had MB check the charging system as well as several independent shops. Even though everything checked fine, I replaced the cranking and battery in the trunk that powers everything else, the Consumer Battery. I'm not getting warning lights, but I do have a bad servo in a headlight. When the Consumer battery runs low, some of the accessories start acting up. For me, that means the Dynamic seats and massage function doesn't work. It's maddening trying to find these gremlins. I still haven't found mine, or changing the battery may have helped, but yesterday the seats started acting up again.
I checked all the fuses and wires and the air hoses that power the seat functions, best I could without removing the seats, and everything looks good. I think ultimately I'll be signing up with Benz Ninja, but I've been to tied up to get it set up. I think I may need a software update and hopefully Ninja can free up my sticky light.
Following, hope to see how you resolve it this.

BOTUS

I suspect these cars are getting old enough the usual kill a Mercedes feature is coming in to play ....

go to the front passenger side - lean in reaching under the dash, grab the floor carpet and peel it back towards the seat squab - you will find unlike a normal car where you can't do this - Mercedes have it so it can - and you find a whole host of electrical stuff and canbus connectors - if its all wet and horrible - this is likely the issue

if its properly soggy you'll need to go round the front under the bonnet and take the battery out - then clean up the mess of leaf litter and mould blocking drains causing it

CharlyS350

For now I have pulled the amp power-in socket. So the discharge rate will drop little bit.

CharlyS350

Thanks much. I'll try that way also.