I suspect that my battery control module (BCM) is bad, though I don't know how exactly to confirm it. I have ran through about 4 batteries in the 3 years that I've had the car and that seems way too high. Right now both batteries are WAY under voltage - 8v for the under-hood battery and 5v for the main battery. The main battery is about 6 months old. The alternator is roughly 2 years old; was replaced (which I am told includes voltage regulator) at a Mercedes dealer. The under-hood battery is also roughly 2 years old.

The reason I suspect the BCM is because there are 4 new part numbers since the original one was released with my car. The car is a 2004 and I have the original part number module, and when I called Mercedes to inquire, the parts guy told me that there were upgrades and that my part number was now obsolete. I have also read posts in this forum saying that the original design was defective...?

The car is a 2004 E55 and is about to turn 97 thousand miles. Any thoughts?? Thanks.

 

Help!!!!
Hello everyone, can someone please provide some feedback on this tread, last night while idling my E55 in the garage I smelled a faint burning scent, popped the hood and could not find nor describe the source of this burning smell, however, after checking the forum on the matter it's come to my attention that the alternator/voltage regulator could be on it's way out, convienience message comes on and off now so i know there is low voltage (11.1v) sometimes a bit less, here's my question,,, if, it is the regulator thats bad, would I still get the burning smell???? Or is the burning smell a clear sign that the alternator itself is toasted internally....feedback please!!!!!!!

 

I smelt a faint burning smell from the trunk area of my car last weekend....

Did you have any other problems with this?

 

The failed bcm is why my car was going dead overnight. The dealer confirmed it when I was out of town and did not have the part. I had to order wait 10 days then it arrived when I got home. It solved my problem. Dealer in Albuquerque was great help.

 

You're the official (and unlucky) 211 expert for annoying problems. You remind me of a great guy over at newcelica.org. Unlucky with his car, but his misery gave everybody else so much knowledge and insight into the car and how to remedy so many issues.

I'm going to be changing my BCM...my entire electrical system is almost overhauled with new parts, lol. I guess it'll be better for me in the long run.

Out of curiosity, what part number variant of the BCM did you install? Did it end in 38 45 or 86 45 ?

 

The part # of the BCM I used is A 211 540 86 45 boughts from parts com

After all of this my patience ran out. I SOLD THE 2003 E500. This is my story and I am sticking to it.

I bought the car for my wife expecting a nice car good reliability. The car was a nice car up to the lot where I sold it. The list below does not include 4 sets of tires for cupping/alignment/caster bolts. It does not include belts 3 sets of brake pads or rotors. On a 1 to 10 scale for reliability I would rate this car a 1 being lowest of any car I owned. IF the car had NO SBC brakes or air suspension it would have been more reliable. I felt after owning and maintaining for 10 yrs I felt that MB sold me a bill of goods on reliability on this car. IT totally failed my expectations based on the number of times I was away from home, had to tow or find a repair shop in a small town and the high cost to maintain. The local dealer however was excellend probably because they had so much practice.

I bought a New Chrysler 300C 5.7 hemi great car. No SBC NO air supsension,, just very smooth and power. If IT doesn't turn our reliable I can buy another and still will have spent less than my E500. IT is truly unfortunate that MB sold me this car as I had planned a S550 for the future but I will probably never buy another MB.

Bought car 2/14/2004 Drove out of show room.
Sold 1/2013 @ 129000 miles. All service was done using MB parts following FSS

Failures
• Cigarette lighter did not work could now power accessories
BCM failed
• Ignition key in dash replaced
• Door locks failed driver door
• How water flow valve Failed away from home drove cold 800 miles home
• Blower motor
• Ball joints
• Rear air springs total replacement
• Airmatic compressor
• Rear airmatic shocks L and R
• Front air struts L and R Flat bed towed in.
• Starter towed in Failed away from home
• Tilt steering wheel failed full up
• Power steering Failed away from home 1200 miles• Battey control module
• Air conditioner Failed away from home drove 300 miles no AC 98 F heat• SBC brake failure towed in
• Flex disc
• Arm rest center blistered up
• 6 headlights … they are on 100% of the time for driving no turn off option.



I really want to thank those on this site for the help along the way. Had it not been for the help and photos owning for 10 yrs would have been way more expensive and difficult. I wish each of you still drivng a MB the very best and happy driving. Hopefully you will gain from what MB learned on producing my E500. Vettdvr...........

 

Vettdvr: Hate to see you leave us, but you needed some relief. Many thanks for the informative posts you made ... a lot of us went to school on you. Good luck with your new car ... and enjoy the ride.

 

I'll still be around and you can PM fo questions. Is your avitar Marines? Looks a lot like the one I wore but mine was sliver.

 

I'm going to miss you Vett =( sad to see you leave after 2700 great and informative posts. Always one of the most experienced experts on here, but glad you finally got rid of that bucket of bolts. Cheers, and good luck.

 

vettdvr: don't blame u at all for getting rid of yours with all the issues you had. i'm very close to getting rid of mine, just figuring out exactly what i want to replace it with for sure at this point. just not worth keeping with all the issues and future issues that "may" (more like will) arise. had the first chrysler 300 limited back in 2006. was not a bad car all around (just had this transmission issue, but that was the 4 speed on their v6 models, not the MB 5 speed tiptronic), obviously wasn't as nice as an E, but the new models are really something in imo, way nicer than the first one. hope she treats you well

 

Here lies the hopes and dreams of Vettdvr owning another Mercedes, RIP.

 

what is left un-said?

 

Hi Guys I don't Have a Reply but a Question ,I am Working on a 2003 E320 ,Does the Battery Control Module also Control The Auxilary Battery Overload Relay ? Got a Red Alert on The E320 went to Check The Alternator it is Fine the main Battery Holds Charge Fine ,went to Check the Auxilary Battery up front No Charge ,The Power Cable had no Current ,fount The Relay and am Getting Power in ,but NO POWER Out going to The Auxilary Battery. Bought another Relay (Used on Ebay ) Hooked that up and I am still getting Power in but No Power to The Battery Yet ,So Before I return the Relay ,Could the Battery Control Module keep The Relay from Allowing Power To Go Through to the Battery ,Any Help would Be Appreciated .

 

Attachment should answer your question.

 

The relay is controlled by the BCM. If system voltage is above 13.5 volts and engine running, the BCM will close the relay so the auxiliary battery will charge. This activation is for 15 minutes or so and will occur once per drive cycle. After charging the auxiliary battery, the relay is opened and is not closed again unless there is a failure/problem with the main electrical system (low voltage). So...you will not see any power coming out of the relay unless you check it during the short charging cycle when it is activated. You can always attach leads to the auxiliary battery and run them to a voltmeter in the cockpit; when the relay closes you'll see 13.8 to 14.1 volts; when the relay opens the voltage will drop back down to the battery value (12.1 to 12.6 volts or so depending upon age and condition).

I recommend purchasing a Solar BA-5 battery tester. It allows you to check the capacity of the battery. FWIW, when my batteries test at ~60% of new rated value, I replace them.

 

Konigstiger Thank you ,and wondering if you Build Models because of your Profile Name ,like these

 

bbirdwell Thank you very much for the help

 

And another lesson at the konigstiger University is complete.
Thanks! I've just learned a lot about my car's charging system and will enjoy having this file as a reference.

 

I had this problem, for me it was the auxiliary battery used for the brakes that was bad and draining the main battery.

 

It has taken 3 mercedes for me to learn my lesson. This is why I'm deleting and bypassing everything possible and just make it a track car. Biggest piece crap car sl55