Doug427

I know everyone is going to scream DO A SEARCH !!!!!!! I did and I'm thoroughly confused. My car is a 2006 E55. I've never had a issue before. Today, out of nowhere, I got out of work and started the car. I immediately got a white "Low Battery Conven. functions temporarily unavailable" message, then immediately followed by a red " Visit Workshop" message with a image of a battery above it. The car seemed to start normally, so I drove it home at highway speeds for 30 min. All was fine. Now, as I got home I turned the car off and re-started it. It cranks, but a bit slower than normal.

So, what say you guys? There is so much conflicting information out there. Some say it's the main battery in the trunk. Some say the aux battery under the hood. Some say it's the one under the hood but they both have to be changed in pairs. Thee are even more conflicting answers, but you get the idea.

Do I need a battery? If so which one? Where's the best place to get one, and what are their respective sizes?

Any and all help in directing me in the right direction would be greatly appreciated.

Thanks.

eFifty5AMG

I'd recommend getting yourself a battery tester that way you'll always know the condition of your batteries. As recommended by bbirdwell, you should get something like a Solar BA-5 to keep track of both batteries. I use a C-Tek unit to keep my batteries topped off pretty much any time I'm letting the car sit. As for replacement batteries, it is recommended to use AGM (absorbent glass mat) batteries instead of lead filled for both the engine & trunk battery. I'm uncertain of the engine bay battery (maybe an AGM motorcycle), but I do know the trunk is a Group 49.

Kalashnikov

This can be a number of things.

1) Auxilary battery going bad.
2) Main battery going bad.
3) Voltage regulator going bad.
4) Alternator itself going bad.
5) Battery control module going bad.

One occurrence of "convenience functions disabled" an "Battery" warning is not enough to make a proper diagnosis.

So check the batteries for their voltage to see if they are healthy. Check for the alternator/VR by opening the voltage screen on dash and seeing what is your voltage when car is off, and what is it when it starts. If car starts and voltage remains 12v or below, then it is your alternator/VR.

rapidoxidation

Read and learn this PDF link from konigstiger
https://mbworld.org/forums/e-class-w...ml#post7329083

Sulaco

you didn't say how old your main battery is (in the trunk)

99% it's that one. the slow to crank thing is a big clue.

tw2

Great PDF link above, thanks. Have both batteries checked and a star scan. After that if normal then consider replacing the voltage regulator. It might not solve your problem but they are cheap and not too difficult to install and if there is anything wrong with the alternator often it is this, if not then it is a wear item anyway so good to do regardless. I have one in a box in the garage just waiting for the day.

bbirdwell

Doug427

bbirdwell, the message on my MFD is none of the above. It's simply red with a pic of a battery similar to that shown above but all it says is "visit workshop". It doesn't specify "battery" or "alternator". I have a second message that pops up in white that says "Low Battery Conven. functions temporarily disabled". I put a charger onit, the car cranks better but the red message remains. The white one is gone. I'm thinking I'll just go get a bew battery and toss it in and see if that cures it.

On a side note, I have read that with some battery type issues the audio system might start acting strangely. Mine is acting up. While listening to MP3 discs in the changer, it will suddenly say "loading disc" and switch itself over to radio. It never did that before. I wonder if it's connected to the battery issue.

Once I replace the battery, I think I remember reading that I have to re-sync certain items in the car. Can anyone lead me to where I would learn how to do that?

Thanks to all!

tw2

Why don't you test it. The battery isn't exactly cheap. Re-syncing things is not difficult, for example the sunroof you hold to the open position for 10 seconds.

bbirdwell

Have you pulled up the voltage display on your instrument cluster and monitored voltage? You should be seeing around 14 volts with engine running. With engine off a new battery will be around 12.6 volts; older batteries will be closer to 12 volts. Be advised I have one old battery I keep around that displays 12.3 volts but using the Solar BA-5 battery tester it indicates only 350 CCA versus >900 CCA new. FWIW, I replace my Mercedes batteries when capacity is down to 50% to 60% of new. The distributed digital control network is robust but low voltages really screw with it.

Youtube has videos on how to pull up the voltage display.

Doug427

Checked the voltage page on the dash - nada on the alternator. Battery is at 11.1 volts, with no gain whatsoever when starting. No smell up front from a burned alternator, so I think I'm going to toss a Bosch voltage regulator in, it's fast and easy and hope that cures what's ailing the car. If not it's time for a alternator I guess.

rapidoxidation

Isn't the regulator a part of the alternator? Might've missed it in a previous post, but how many miles are on your car? If it's in the 6 digits, I'd just put an alternator/regulator assembly in and be done. If you wanted to go crazy with it, you can have the alternator tested at the parts store to make sure you're not wasting money.

I've yet to "smell" a bad alternator. Just replaced the one on my '05 Chevy Duramax last week (240K miles on it, not bad) and other than not putting out anything it showed no sign of duress.

Doug427

From what I have read, if the alternator doesn't show evidence of overheating or burning, there's a decent chance that the very easy replacement of the voltage regulator, which just screws onto the back of the alternator, will solve many problems. Of course there's a chance it won't work, but I look at it like this. The voltage regulator is only about $40, and takes about 20 minutes to install, it's a very easy job. The alternator is about $250 - $350, and it's a pain in the *** to do. I'm basically gambling $40 that the regulator will work as it has for many. If not I'm out $40.

rapidoxidation

Makes sense.
Keep us posted on how it goes.

Bahnstormer

I replaced the voltage regulator on my 2003 E500 today.
Used a Bosch unit from eBay that cost $40 and followed a couple of DIY threads.
Took me about three hours but I ran into issues with not having a deepwell 15 mm socket.
Tight quarters underneath with the car jacked up but I managed to get it done.
Drove around for about an hour afterwards and no more "Malfuntion, electrical components switched off" messages.

Doug427

Wow, three hours? I was hoping it was quicker and easier than that. Any tips, having just done it?

Bahnstormer

Yeah, if I had to do it over again it would probably take about an hour.
Make sure you have a deep well 15mm socket for the second nut on the passenger side.
That bolt has two nuts that have to come off to get the cover plate out - that stumped me for awhile.
The top nut on that side was 13mm and underneath was another 15mm.
Other side of the unit (towards the driver side) has one 13mm nut.
There was also a philips head screw on top to remove and then the cover plate comes off.
Three more philips head screws to remove the regulator itself and then pop in the new unit and reinstall everything in reverse order.
Not a lot of room down there and very difficult to see.
Anybody that can do this job in 20 minutes is some kind of god.

StarvingArtist

Wouldn't hurt to charge your battery before you start it with the new VR.

bbirdwell

bbirdwell

Doug427

The top screw on the regulator is almost impossible to reach. Now, the Phillips head in that screw is stripped. I have to take the whole alternator out, which is exactly what I was trying to avoid, as it's a pain in the ***. Ugh

bbirdwell

You'll want this DIY then...

https://mbworld.org/forums/w211-amg/...r-removal.html

Doug427

Thanks, about to start on it now.

Doug427

Just got finished with the voltage regulator replacement. It doesn't work. I still have the convenience items message and the red visit workshop with a pic of a battery message. Is there something else I need to do to get the alternator on line? I checked the voltage and it still shows no increase in voltage after the car starts. The battery in the trunk checked out ok. I need to just step away from the car right now, as putting in the regulator was a real pain. Had to remove the alternator to do it because of one small stripped phillips head screw. I have no idea where t go from here. I guess a new alternator?

tw2

Sorry if I missed it but did you end up hooking the main battery up to a proper tester first?