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W221 s350 bluetec red battery light / no charging

Discussion in 'Electrics, Vacuum, Ignition and ECU' started by alex_78, Oct 11, 2018 at 3:03 AM.

  1. alex_78

    alex_78 Senior Member

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    Location:
    edinburgh
    Your Mercedes:
    w221/2011/s350
    hello

    long time no seen (car was going surprisingly good for a while...)

    i have another problem this time battery related...

    few days ago after driving for few hours (everything was ok) i switch engine off to go open gate then i switch engine on drive in and big red battery symbol shows on central display (speedo)

    next day i open vehicle data menu (ok+Call) and after switch engine on voltage goes up to 14v which means alternator works ok

    next few days all good no battery light at all (driving every day for few hours)

    tonight same story after driving (few hours) switch engine off then switch on red light go on when check ok+call vehicle data shows 12v so alternator not working
    (i check it again tomorrow )

    it was no burning smell, no weird noise etc no problems before so for that reason i think is more like electronic glitch than mechanical alternator failure

    what you guys think voltage regulator?

    i think battery in my car (late 2011) looks like original do you think this error can be caused by old battery?

    my guessing:
    1 voltage regulator
    2 old battery
    3 mechanical failure of alternator (car late 2011 milage 118k feels like to early for that)

    any suggestion welcomed

    how hard is access to voltage regulator in om642 engine in s class w221? i read on some merc models can be done without removal of alternator

    thanks in advance
     
  2. OP
    alex_78

    alex_78 Senior Member

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    Your Mercedes:
    w221/2011/s350
    update:

    i started car for few minutes, starts ok, charging over 14v so alternator works...

    i think it can be some electronic glitch coz problem show up after few hours driving switching off then on engine but second time in a row after few hours of "resting" when start car again it works ok

    question is:

    1 battery as mentioned is looks like is from new - is that possible that old but fully working battery can caused problem with charging by alternator?

    2 voltage regulator but i think is a lot of labour to remove alternator to investigate or can be done without removal (access to regulator om642)

    3 any other suggestion?

    looks like car start to give me warnings about incoming expenses but hopefully it happen after i comeback from holiday ;)
     
  3. tode

    tode Senior Member

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    Your Mercedes:
    S350 btec 2011
    Hi,

    I have the same model, same year and had the same message last year -turned out to be the small battery in the boot.

    Battery changed and OK since.
     
  4. John Laidlaw

    John Laidlaw Senior Member

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    Your Mercedes:
    W212 E63 ///AMG V8 Biturbo Volvo XC90 2018
    These cars do not like low batteries, that’s for sure!
    2011 battery I would replace anyway- I only keep mine a maximum of 5 regardless. Often you get no notice at all before failure. As mentioned the second battery is worth checking and if it’s poor, replace it too. Not worth the hassle
     
  5. OP
    alex_78

    alex_78 Senior Member

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    w221/2011/s350
    thanks

    ok i will replace battery once come back from holiday

    about second battery i think my car have only one

    i inspect boot when i was fixing amplifier (left side)
    under matt is only spare wheel and adblue tank
    behind rear seats only fuses and i don't see second battery on right side

    maybe im blind or is well covered somewhere?
     
  6. John Laidlaw

    John Laidlaw Senior Member

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    I believe it is in the panel between the boot and the passsenger rear compartment, probably a pain to access! See attached
     

    Attached Files:

  7. tode

    tode Senior Member

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    Your Mercedes:
    S350 btec 2011
    ^^ This is correct: 12V, 12AH, ref. A0019822708.
     
  8. OP
    alex_78

    alex_78 Senior Member

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    Your Mercedes:
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    I just checked boot i will try attach pics, is none battery there between boot and seats just fuse box also is no mention about second battery in owners manual, are you sure that facelift have 2 battery?
    Main engine bay battery looks big enough what is amp of battery in your car?
     

    Attached Files:

  9. John Laidlaw

    John Laidlaw Senior Member

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    Hmmm, wonder if the FL reverted to a single battery? Sorry I’m just not sure
     
  10. OP
    alex_78

    alex_78 Senior Member

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    ok i google part number provided by Tode

    looks small like can fit under fuses

    ok i went again to car and go into boot access fuses box from pic above remove bracket and im 1000% sure is no battery there
    is only wires underneath connected to fuses

    so or i have one battery or i need angle grinder to remove metal floor and start look there ;)
     
  11. OP
    alex_78

    alex_78 Senior Member

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    @tode

    as you mentioned you have exact same model is long or short wheel base also do you remember by any chance location of small battery?

    my car is s350 short wheel bluetec bluefficiency with adblue tank euro6 but is NOT start/stop model if this relevant? (i know in this years was few different variant of s350 diesel)
     
  12. John Laidlaw

    John Laidlaw Senior Member

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  13. OP
    alex_78

    alex_78 Senior Member

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    that looks excatly like what i have in my car...

    so i guess i start from replacing battery and if that no help will be looking further probably voltage regulator on alternator but fingers crossed that is caused by old battery

    thanks very much John
     
  14. tode

    tode Senior Member

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    Your Mercedes:
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    Mine has the Stop-Start, is a standard wheel-base and definitely has a small battery in the boot. If yours has no Stop-Start, it's quite possible that you only have the one battery in the engine compartment.

    I would have thought that a 2011 model would have had the two batteries, however (the Stop-Start was not an option).

    Are you sure that yours is a 2011 ? Have you had your data-card ?
     
  15. John Laidlaw

    John Laidlaw Senior Member

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    You’re welcome Alex apologies if I sent you the wrong route first time !
     
  16. OP
    alex_78

    alex_78 Senior Member

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    yes im positive accordnig to vin delivery date 14.03.2011 then first registered october 2011

    i live in UK and trust me things here are different than in rest of the world ;) ;) ;)

    some cars models years are totally different
     
  17. OP
    alex_78

    alex_78 Senior Member

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    all good you are the men, that video kind of explain that this sensor on clamp can make this mess, thanks again
     
    John Laidlaw likes this.
  18. OP
    alex_78

    alex_78 Senior Member

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    ok so i start look for new battery

    what you guys think is better to go for same as on car from dealership or take this one:

    https://www.tayna.co.uk/car-batteries/exide/ea1000/

    i start google and this comes as replacement by part number and have very good reviews, exact same dimensions

    my only concern this is is 100Ah 900A when original is 95Ah 850A i know usually bigger is better but since this car is so delicate wth his sensors i just want to buy something what gives me peace of mind

    so what is your verdict:

    -merc genuine
    -exide
    -other suggestion

    im not worried about few £ difference i just want to buy good one
    thanks
     
  19. tode

    tode Senior Member

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    After having tried many makes of battery, I always buy Bosch. They are a bit more expensive than others, but do last longer.

    And are often OEM.

    PS although in France, my 221 was bought in England (Ealing, to be exact . . ;))
     
  20. John Laidlaw

    John Laidlaw Senior Member

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    Nothing wrong with the battery choice but do give MB Grangemouth a call 01324 686002 , they will give you a genuine battery with a forum discount and £5 delivery in the UK
     

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