Over the past few months, I've had the occasional "Convenience Functions Disabled Due to Low Voltage" message, but it always cleared up after a couple minutes of driving. Starting about 4 weeks ago, it became more frequent, so I started checking voltages.

With the car off, the main battery was somewhere around high 13.x volts in the morning and the AUX battery was whatever the acceptable range is considered. When the car was running, the main battery was somewhere in the low 14.x volts. I figured it was most likely the battery, but then got busy and was unable to look at it again for about a week.

The next time I took the car out to run some errands, I was stopped at a light and the car flashed a red warning light across the cluster about low voltage. This went away as soon as I left the light and I made it down the street to my destination with no problems. I then located the nearest auto parts store and drove right over. At this point, I had no dome lights or power to the radar from the lighter, so I knew it had cut features pretty heavily.

I purchased a new battery, then took it out to go home and install it, but the car wouldn't start. Ended up replacing the battery in the parking lot and it started right up. Car started beautifully for the next 2 weeks, but then started developing this odd sound over the last few days, almost like the supercharger, but more "wind tunnel" like. It rises and falls with RPMs. I also thought I smelled a strange burning smell at times, but no one else could confirm it.

Yesterday, I went out and the dreaded "Convenience Features..." message was back. This time, it did not turn off. I was taking my dad to the ER (another long story), so I couldn't exactly turn around and head home. After a few hours there, I left him with my step-mother and headed home. The car displayed the "Convenience Features..." message all the way home and ,again, the interior and power outlets had been turned off. I worried all the way home about the car dying. I was too worn out from the day's events to do any testing last night.

Tonight, I went out to test the car and the rear battery showed ~10.8v. I started the car to attempt to get a reading on the alternator and only got low 11.x volts with the the entire dash a bright red telling me to turn the car off.

So, with all of that information, where should I start? Voltage regulator or alternator? Why would the car charge fine before the old battery kicked and now charge like crap?

Edit - Dad ordered me a freakin' nice battery charger and system tester and they arrived tonight. Talk about good timing. I've got the battery charging now and I'll start using the tester tomorrow.

 

You probably need an alternator. Get a visual of your copper windings and see what color they are. Mine were blue and black when mine failed.

 

start with the VR, much cheaper and easy fix with alternator on the car. Then again usually when you smell somethings burning its game over for the alternator. When VR goes out it usually stars acting up and causing all this hassle before failing completly!

 

if you smell something burning, then probably alternator related, VR or other part of alternator. I would change the VR first.

I had problems with mine a couple years ago.

changed trunk battery
changed smaller battery
changed VR
changed Battery control module in trunk
changed battery relay under windshield

Beginning got the low battery convience function temp disabled. progressed to red battery code. Viola, red battery code finally went away after 5min idling. I even bought a new alternator thinking that would be my last straw to change if i still got the red battery code.

 

Ran a system test tonight. Battery health is good, but the alternator output is only 12.1-12.3v. *sigh*

 

Post back here about the purchase and install.

 

Do the regulator first. Mine did the same thing. Fixed after i replace it

 

Sounds an awful lot like my own personal experience.....

Electrical smell should be the warning sign, maybe just the regulator but probably the alternator.


https://mbworld.org/forums/w211-amg/...ing-light.html


-G

 

Regulator is $30-40 + shipping time. Alternator was $160 + core @ Orielly and it can be here at 5:30 today. Went with the alternator.

 

nice find.. looks like the alternators have dropped in price. I picked up a new bosch one from amazon a couple summers ago for close to $200, no core return required.

 

Real good price on an Alternator. I replace mine with one from the Stealer and I paid the mb tax - $330 + core.
GL

 

Damn! I looked it up on OEDiescountParts last night and they wanted $900 for OEM.

Historically, I've had good pricing with OE.

 

Always good to know someone at the dealer

 

You can get a Bosch AL0826N for under $300.00...OEM part and lifetime warranty.

Let me know if you need a hand with the R/R of the alternator.

 

I think you are doing the right thing here. 10 year car, may as well just replace the whole alternator, especially if it is only $160.

Let us know how this works for you .. I have read on the forums where several people have had issues with anything other than OEM alternator. Hope this works out for you.

 

It is incredible that I am having the same issue...changed both batteries and after leaving the car sit for 24 hours, the 'Convenience functions' light comes on again. Drive the car for a couple days and it hasn't come back on but it hasn't sat for more than 24 hours either. Going to check everything tomorrow and replace anything that 'might' be bad! Don't want to have that red light come on when driving to FL., 1100 mile trip! YIKES!

 

Oh, so this is your fault!

 

It's these f'in white cars Heiss!

 

Well, that was a *****. Had to take the fan shroud out, but in order to take that out, I had to take the header panel out. Then a few coolant hoses had to be disconnected or pulled out of the way. Way more work than I thought it would be. Hardly any room to get the alternator out of it's "pocket". Also had to use a file to shave a few millimeters off the mounting surface of the alternator in order to get it into the mounting ears on the block.

To anyone attempting this, you will need...

• Reverse torx sockets in E10 & E12 to remove a bracket from the corner of the valve cover
• A reverse torx socket in E14 for the alternator mounting bolts
• A T-20 torx bit for a bracket on the bottom of the shroud
• A T-30 torx bit for two bolts on the header panel
• A 5/8" 12-pt socket (or metric equivalent) for the belt tensioners
• A crow's foot screwdriver to pull plastic clips
• Size 8 hex key, if you have a belt wrap kit
• 10mm & 13mm sockets for various places

 

I have never installed or taken out the alternator. But, could you have removed the alternator from the bottom vs the top?

 

No. Subframe is in the way in the back and hard lines are in the way in the front (a/c or cooler lines?).

 

Heiss, just curious, did you check the VR and is the VR attached to the alternator? Also, you got an alternator for $160? Sounds awfully cheap!


One more thing...Friday I did some minor stuff to lights and so forth so the key was on for a good hour or two and afterwards I wanted to check the voltages. Coming from alternator there were 14.1 volts and at the rear battery was 13.87v. My buddy said bc we had the key on for a while that this all seemed normal but he is NO benz expert! lol Any thoughts here that I should check this again when it has been charging more?

 

Both Orielly Auto & Autozone offer alternators for $160.


It doesn't hurt to check it again after your alternator has had a chance to recharge what was spent with the key off, but I agree with your buddy's observation.

 

I also have my pump running constant so maybe that draws a little too. Thanks Heiss!

 

the Voltage Regulator? Either Bosch or MB? Thanks...