Hi all,

Your help is appreciated. About a month ago, car started dying, jumped it about 5 - 8 times. Took it to autozone (it has a duralast gold batter about 3 years old) and they tested it and said the voltage regulator was bad and that was replaced.

It was doing well for the past 3 weeks and then it started dying again.

I went into the engineering menu, on idle it reads 12.5 - 12.6 volts (confirmed with a multimeter).

I've read about the smart alternator on mercedes so wanted to confirm this is normal function. While driving or on idle with the fan on high / max all 5 notches voltage will increase to 14.3-14.6 or so and then drop down to 12.5 to 12.6

While driving the only time I could get the voltage in the 13 - 14 range was when coasting above 60 mph but then would drop down to 12.6.

My auxillary battery has also not been changed, and when it is cold in the winter I will get aux battery malfunction, so I was wondering if I should start with new OEM or equivalent batteries and go from there or could the alternator / VR be a culprit.

I've tested it autozone twice and they say the battery is good, and they tested the started system and it read 12.5 volts and he said it should be 13 - 14 and your alternator is bad, but after reading about the smart alternator I'm not sure
thanks

 

IS the battery fully charged when they test?

What is voltage of battery when it does not start?

Have aux battery charged and tested.

Proper to only test battery when fully charged

 

No the battery is not fully charged when they test it, it said low battery but functioning on their machine or something like that

I do not remember what the voltage was when it wouldn't start. Will keep an eye out for that - I want to say it was 11.75 but I'm not sure

 

2010 is what you have in your profile and from what I read it wasn't till 2013 when recovering charging system was introduced.
Your charging system should keep min 13.5V and when it is not- it is either VR or charging module.

 

yep I have a 2010, could be but according to this post it may have been a bit earlier

https://mbworld.org/forums/e-class-w...-question.html

 

So I have a 2014 w212, and I just drove it around and the voltage is between 13 - 14 when driving it. So I don't think it is a battery issue any more, it's only charging when the fan is on full blast / reverse / or coasting ?

any ideas?

edit

https://mbworld.org/forums/w211-amg/...ammed-vin.html

could this be the battery control module ? another thought is the alternator was removed when the voltage regulator was changed, could they have improperly installed it, and that is why it engages when on its highest level

edit

load tested it at that point the voltage did not dip below 11

will check the car in the morning and rule out a parasitic draw overnight versus some other issue

 

Good day - So this might be the issue - So our Mercs have a smart charging system, it will request voltage\charging from the alt. when it needs it, This programming it to help with fuel eff. so its not just charging all the time. There are various programming modes the car can be given. I know this because the techs changed it for me on my car...(or at least thats what they told me and I could see it when i added in a volt meter than ran all the time...

At least its a path to look down...

Cheer

 

Has your car's starter been changed yet?

This forum has lots of writing about it. I have a 2010 model and had exact same issues as you describe. First had the dealer change the battery for about $400 or so. Worked fine for starting for a couple of months but then had starting issues and sometimes the car lost power to other electronics like Distronic would not work. Had to stop and start again to get all systems going.

Purchase a AutoZone battery and again everything worked fine for a couple of months and then starting and other issues returned. This time I did not go replacing battery again but went and got a new starter and replaced it. AutoZone starter with life time warranty cost about $300, installed it myself.

No problems since starter change at all so far and it has been almost 3 months now. Starting of the engine improved a lot.

It appears the starter gets old and starts pulling too many amps and robs the car from power to actually start it. It cranks fine but no start with worn out starter.

If your car still has the original starter it is time to replace it.

 

I had these symptoms with my 2001 C320 after 6 years... I'd drive the car somewhere and park it, return to the car 10+ minutes later and it refuses to start. Jumpstarted easily the next 3-4 weeks. Eventually died pulling to a stoplight in heavy traffic. Towed to MB dealership.

--- Crankshaft Positioning Sensor.

 

My 2010 model has this "smart" charging system. It only gives 12.6-12.7 volts during normal driving but on highway when you let off gas pedal it jumps the voltage up to 14+ volts for the time the car is decelerating..

Today driving 5 hours on highway at 78 MPH and 83 MPH depending on speed limit with cruise control ON. At constant speed it shows 12.7 V for HU voltage and 12.6 V for CAN. This with wipers and head lights ON. Rain got very heavy so I turned the rear fog light ON. This increased the voltage exactly by one volt for both, i.e. 13.7 V for HU and 13.6 V for CAN. Checked for this several times with and without the wipers with the same result so my car does not give13.5 V and higher charge but also lower when there is no demand for higher charge.

 

thank you this helps a lot, since the charging was so different from my 2014 w212 so it looks like it maybe charging properly,

its at 12.2 volts I'll see if it drains overnight and then start digging.

I've got a handy jump starter kit like this so I'll just continue to figure out what is going on.

this is great btw for when your w212 gets a little older

 

no it hasn't been changed. I'll look into that. Waiting for it to die again, I think it will in the morning and then I'll start digging some more and ill look into the starter

thank you

 

Your car battery does not really die. It just goes low enough voltage/charge that the bad starter makes it fall on its knees and there is not enough power in it to get the car actually started. There are many stories like this in this forum. This is why I changed the starter and I really believe it was the culprit, not the battery or alternator/charging program.

Your starter is nearly 10 years old if not already 10 years. My car was built in Mat 2009 and put in traffic mid September 2009 so in a couple of months my car has been driven for 10 years. Changing the starter is not a bad investment even if it has not failed yet as it will come to the end of its life cycle soon anyway.

 

+1 for Arrie's response, it is the starter.
I just repaired mine a few days ago and my slow start, long crank, light dimming when cranking, etc. have all gone away. I chose to replace the brushes and the solenoid push arm cradle rubber bushing, a 50$ repair which allows you to keep your original starter.
The car feels like it has a new motor, the cranking is way faster than before and no more ghostly light dimming while cranking.
4matics are a bit difficult because the starter is on the driver's side and you need to remove the exhaust portion from the header to the mid cat. Nothing too crazy, it can be done with one hand if you want to prove a point to some non believers.
Before the repair the car took up to 3 seconds to start (kept cranking), after repair it's 1/4th to 1/2 of a second to start, every time. I didn't have to do anything to the battery, no charging or reconditioning.