L8Apex

Driving home today after a little spirited driving my Command screen had a message "Low voltage comfort and command will shut down". The AC stopped working command shut down so I took it in to MBLN. My tech said the battery was going but we also noticed a plastic smell coming from the engine bay. Plus it sounded like the bearings in one of the pulleys might be on their last legs. I should find out more tomorrow.

WARNING! I also learned a lesson about our electrical system. For those of you that do not lock your car at night the car does not shut down the systems causing the battery to use power. (SBC, airmatic etc.) Eddie told me that when you lock the car it goes to sleep and reduces the power to the car by shutting down other systems. Now I know.

Jrocket

My car lost all battery power over night once.Ended up being the (sams)?

I thought these cars auto locked after a certain time peroid?

jangy

No disrespect to "Eddie", but I rarely lock mine in the garage and it has sat for weeks without an issue.

I had a similar issue with an '04 and there was a DTB for it. Something was draining the battery and I forget now. Look up all the recalls and technical bulletins in the sticky thread to see that it gets taken care of properlike.
what is the deal with your bearings? Can you elaborate? That is scary.

jangy

By auto lock, do you mean lock the doors, or shut down? They do not just lock the cars. If you had it locked and unlocked it with the key but never openned the door, then it will auto re-lock after a few. Maybe that is what you meant.

Jrocket

Thats what I was thinking ,yes.


The sam module is what drained my battery down over night.

psk145

Im locking my car at night now just to be safe. Thanks for the heads up!!

CynCarvin32

Same thing has happened to every W211 I have ever had. Same exact sequence.

It is the rear sam having a short. Have it replaced. They will have to test the issue buy looking for the part that is shorting. Its a realy BIZNITCH to find but just tell them its the rear sam having a voltage issue.

Good luck

CynCarvin32

And the bearings on these M113 motors just sound like poop. Its all normal. You can tell when one is bad as it will become extremely loud. The pullies for some reason are just loud as heck. I think its cost cutting at its greatest!

psk145

whats the "sam"??

jangy

computer module.

CynCarvin32

The car has places where all the modules plug in and connect into the cars central CAN Data Bus system. The one in the rear goes by the term rear sam.

It must be a very flawed item as I have had 3 cars fail and I have seen many others having the same exact issue.

To bad as its a real pain and very hard to find. The issue comes and then vanisheds. My cars just started throwing every random error possible. It happens because the car has a short and it starts losing power. When it loses power it starts shutting off non essential items in an effort to keep the car running. Once the short is over it all comes back on line. Sometimes the car will not store any codes as it all goes back to normal pretty quickly and at that point its just you telling the shop foreman the car is acting like a nut case. I had pictures and pictures of warnings and idiot lights going off but the warnings do not get you any closer to the real cause as its just the cars reaction to losing power.

Vetluver

Which battery went down?

The one under the hood or the one in the trunk.

As I understand the battery in the front is the one that powers most of the convenience items, such as the command, AC, power seat auto motion etc. Although low voltage in the front battery will shut things down, if your battery in the rear is ok things will still function.

My car shut the convenience items down because of "low voltage" when I checked my voltage by pushing reset 3 times I had a reading of 12.3v. My SA said that my front battery is going south. They are going to change it out.

CynCarvin32

Well I am unsure as to which batt does what but I was told that the front batt is for the main core features that make the car run. I guess that second batt is there to keep the electronic brake system going in the event of a power failure on the other batt.

In this case there really is not a shortage of power (if he is having a rear sam issue) and it is more of a problem with what the computer is seeing. It could be getting a slight short which causes false readings from many of the cars control systems. Once it all gets back to normal the car just runs great and the batt's will show perfect voltage.

Maybe I should confirm that he is having the car give a reading than "shutting down the convience items" for that is just showing that the car has a low charge on one of its batt's. My cars kept showing errors such as, malfunction cluter, malfunction tpms, malfunction ASR ESP BAS, malfunction with the key etc... It also had the ac system go out, the command system shut down, the dynamic seats shut off etc. It would go in spats where it would all freak out, recover, and be back to normal in a series of maybe 45 seconds -- most of the time.

2K6E55

I never lock my car at night time when parked in the garage and my battery does NOT drain?

vader

I got that alram too a few weeks ago....turns out my rear battery was very low. I was sitting listening to CD's in the garage a couple nights while working on other stuff....I ran the car a while and it was fine. I bought a CTEK charger to top it off and to my surprise...that charger ran for 2 days until it went into maintenance mode so the battery was very low and probably on the verge of going bad due to sulfation. The CTEK brought it back up to snuff. These are really good chargers. I would try charging it up with a really good charger.

starbrite

Vader...that's a new charger name to me. What model # did you use and how does it compare to the Deltran Battery Tender ?
A quick Google search shows made in Sweden and the US 3300 the most likely one for cars. Seems available online or on Ebay around $70.00.
Also seems small and very thin cables ? Comments welcome please.Thanks

vader

Thats the one I got...I love it...it has some great features to keep the battery optimal..I leave it on 24/7 since the car is stored for the winter...Maintains perfectly...small,lightweight.

starbrite

Wow...I'm glad I caught your post, I was just about to buy the BTP*.
Even though it's touted as a battery maintainer, I like the 3.3a vs the *Battery Tender Plus 1.25a.
Interesting reading re this charger online, deceptively small though.

L8Apex

I picked up the car today. The diagnosis was a low main battery charge, which shut down the comfort and command. They recharged both batteries and everything is back as it was before. They reemphasized the importance of locking the car when not in use for long periods of time. This will decrease the cars battery use. Given the fact that I never locked the car at night in my garage for over a year, it makes since.

They also replaced the air pump (recall) and reflashed the car and updated the command software. I must say, the car runs great (very strong). This is the second reflash that the car has had. I did notice a higher pitched whine (supercharger or air pump I think). Sounds pretty good.

They did check the rear sam and found no issues. As far as the bearing noise it's gone and they could not repeat the issue.

enzom

Same with me. I always remove the key from the ignition and put it in the cupholder. I never lock it in the garage. Sometimes it sits for 7 days or more without being started.

I know the car comes "alive" when I open the door, as I hear all sorts of buzzing and whirring sounds from under the hood.

All this talk about front battery and back battery has got me confused. If I wanted to hook up a battery tender, where would I hook it up? (sorry for the semi-hijack)

starbrite

Hook up to the main battery, which is in the trunk.
Just because your car "comes alive" after 7 days doesn't mean your
battery isn't substantially discharged, which will shorten it's life.

vader

I think its important to hook up the float charger if you dont drive it for several days at a time too.

starbrite

...and or/if you only drive a short distance. I believe I read somewhere that after starting,
you have to drive at least 15 miles for the battery to regain the starting voltage/amps loss.

L8Apex

Well it's been in 4 times now for the same problem. Today is the 5th! This car is driving me nutz. The dealer has replaced the battery, battery module and several other parts. Still not fixed. I've been driving a c240 more than my 55!

Any ideas? I had them check the alternator, sam etc. still nothing. All I get is a Visit Workshop warning with Battery symbol.

stevebez

I mostly drive the car on the weekends and almost every time on startup I get the message convenience functions temporarily disabled - 5 mins later after driving all is fine.

Is this normal. Sometime I have drives of an hour or so on highway - surely this is enuf to get the battery (both) to full capacity?