AWOL

Im having major electrical issue/voltage problems now.

basically the same as this:

http://www.justanswer.com/mercedes/3...x-battery.html

same codes and everything

In this link he mentions testing the aux battery fuse, but I cant find it. I only see the battery and misc. plumbing lines.

Either my BCM is dead, or has an open fuse.

AUX battery has 12.7 volts, rear battery 12.2. The rear drains in no time

AWOL

found it, still works.

blackbenzz

The rear drains in no time with the car on or off? You sure your alternator is working?

AWOL

The dealer says its charging.

I have 3 codes, no cel's.

9092 Component G1/7 (Auxiliary battery) is defective or not installed

9071 Component K57/2 (Auxiliary battery relay) or the signal wire to the component is faulty

9055 The terminal 61 signal on the CAN bus is missing or is faulty.

I checked that fuse, its fine. The dealer thinks I have a draw somewheere.

I think its the BCM itself, as the volatge is capapble of hitting 14.0+ at times, and sporadically drops down to 11.5 when driving. Its all over the place, ergo, not a constant "undercharge" and I think the N82 BCm is to blame.

novae500

I fully charged my auxillary battery on Sunday after seeing all of these posts using a Ctek. Didnt get a chance to do the rear main battery. Wed i noticed the convenience functions unavailable when i started it up on Thursday leaving for work in the morning. After 30sec it went away. I'll charge the rear main tonight and see what happens after its fully charged. On the same OEM battery since 05.

Where is the BCM located and how much to replace it?

AWOL

Its in the rear, by the spare tire. Its a little black box. Its big money, $600+ from what i gather

urbamworm

Just throwing stuff out there but maybe you have a bad ground wire/power wire or bad connection? I have had a wire go bad in my Audi which was causing the battery to not get the charge it should. The alternator tested as putting out what it should (13.5 range) but testing at the battery it was at like 10 or 11 if I remember right. I ended up running a new power wire from the alternator to the battery positive and it worked like a champ. I think one of the wires went bad that goes from the alternator in to the fuse box and then to the battery. I would try testing the voltage at the battery if you haven't while the car is running and see if it is getting the same voltage as the alternator is putting out.

Bramage

I had some similar issues when I first got the car. My mechanic said to replace the AUX battery, and that solved the problem, I was not getting any CEL's, but I did get the convenience notification. Just a thought.

AWOL

The auxiliary battery is the diehard bs-14. Its fully charged and shows 12.7 volts whether the car is off or running - no change in voltage.

PS, I think my only key is in my trunk, with the battery unhooked. Im boned

AWOL

Is there a jump point thats not in the trunk?

I know BMW's have a jump spot under the hood, I cant find anything. Help please

Eclass2003

where did you find the fuse of the auxiliary battery?

Elhonaz

no jump point. if you can get the doors open, pull front passenger carpet and remove the cover. Under is prefusebox fuses and a power cable you can hook it up.'
edit
lol.. just saw that the last comment was from 2011..

Eclass2003

I did changed my auxiliary battery and I still get the red battery on!! Any other solution

Nevell1

I have a 07 S550 W221 just replaced both batteries and alternator. Still getting red battery light. Front battery 13.7volts and rear battery 11.2 volts. Could this be a bad relay?

gfmerc

i have a s65 w221 same problem as you......i was thinking a relay that is open to drain......did you find the relay what was its official name called ?

gfmerc

The result was a stuffed alternator. I was offered from the dealer a remanufactured alternator or a new Alternator_A0131540602 Bosch 0121813102_$2208.40 AUD.
Refer to attached Merbuk.de I was shipped a RNL one up for $720AUD from the netherlands

qbmg973

you have a actual key that slides out of ur car key which unlocks the trunk no power needed I suggest leave a battery terminal loose when not driving the car and do this until it’s fixed unless you want to run thru batteries cause the draw will eat your battery if the car sits unattended

cdk4219

Hopefully he fixed his car since the last post in 2011.

nd-photo.nl

Nevertheless good advice

Dont forget to align the windows + sunroof (if you have one) after connecting it again. For the doors is holding down for 15 seconds and up 15 seconds, if I remember correctly (repeat for all 4 doors). For the sunroof a tad different: