vincent52100

Hi all. I've gots 04 S500 with around 160000 mile. It's deveined a wierd problem. A couple of weeks ago the battery went dead. Charged it up and checked the charging system (14 volts). A couple days later it was dead again. Both times it was running the night before. I had the battery replaced and it seemed to be fine. This morning it was dead. We had used it two days before with no problems. There were no dash lights on before or after the battery replacement. Also after the battery replacement the remote stopped working. Replaced the remote battery and it still didn't work. Any ideas? Thanks

tusabes

You have to pinpoint whether it's a bad battery , or a battery drain issue where the car isn't completely shutting down its electronics .

often times the navigation system or alarm
siren box go bad with age , and are responsible for a battery drain

what I would do is buy a battery brain t3 from Amazon . It's a remote control battery disconnect that will completely disconnect your battery by clicking the keyfob they provide. It simply attaches to the top of the battery . If this solves the battery drain issue then you can move into diagnosing why your car is draining the battery

vincent52100

The battery is only a couple of weeks old. It was completely drained this morning. I've got it charging. I'll test tomorrow for current draw with everything off. I like the idea of a remote battery shutoff. Thanks

tusabes

Looks like Amazon is all out of the battery brain t3

they have one by Ekylin for $49
search Amazon for remote battery disconnect

vincent52100

I got a chance to check it today. With everything turned, trunk latched etc, it's pulling about 2 1/2 amps. I pulled each fuse one by one and it basically stayed the same. I think I got them all, right side engine, left side engine, right rear seat. Did I miss any? I wonder what could be drawing that much current with the key out. Any ideas would be greatly appreciated.

wallyp

There should be another fuse box on the right end of the dash. There is a hard-to-remove cover over the panel - open the door, and look carefully on the now-exposed end of the dash.

vincent52100

Thanks very ugh. Will check those also.

vincent52100

Is there a fuse or relay that will disable the scm? I know I can unplug the wire harness under the seat but when I get down I have a hard time getting back up. Way too much wear and tear over the past few decades.

amstel78

A 2.5 amp draw is significant. There's something that isn't turning off... question is, what can draw 2.5 amps? ECU perhaps?

Anything significant happen prior to this? Anything replaced? Did the car go through major rain storm?

vincent52100

No, nothing. Just came out one day and it was dead.

eurdone

Were you ever able to resolve this problem. Exact same issue on my '06 S55. Same massive draw when the car is locked. Discovered the audio gateway seems to be staying awake. Seeing optical light staying on when the car is off. Drain so strong it's killing my battery overnight. Really don't want to replace the AGW. Any update would be great. Thanks!

pmercury

iTrader: (2)

start with a Xentry DAS diagnostic instead of guessing
ever searched on internet for having pain somewhere ? seen the results ? stop guessing

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.

tusabes

Buy a remote control battery disconnect from Amazon or eBay

Fried Chicken

Current draws are nasty to diagnose.