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ML63 Charging Voltage suspect?

Discussion in 'AMG' started by Nawaz SouthSudan, Jul 5, 2018.

  1. Nawaz SouthSudan

    Nawaz SouthSudan New Member

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    Joined:
    Jul 5, 2018
    Your Mercedes:
    ML63 2007 6.2 AMG
    I bought an ML63 6.2V8 in November 2017. The starter "felt lazy" so took it up the motorway - 200miles later - no improvement. The charging voltage after 200 motorway miles was an indicated 12.4V on the dashbord.

    So changed the battery for a new MB from dealer in March 2018. No improvement.

    So changed the alternator - new MB from dealer in June 2018. Charging improved to 13.4V to 13.7V on the dashboard. When measured with a Fluke, it is over 14V.

    2 things:

    1) Starter still "dips speed" on cranking-turnover - even with a warm engine before ignition...

    2) Very puzzling: when you "blip the throttle" - voltage goes down before increasing? How?
     
  2. alexanderfoti

    alexanderfoti Moderator

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    Location:
    West London
    Your Mercedes:
    W221 S65 AMG - W204 C63 AMG + Various other MB's
    1) Possibly faulty starter?

    2) There is a one way pulley on the alternator and active charging management by the engine ECU. This will remove/reduce charging under certain conditions (overrun = max charging, revving or full throttle = minimum charging).
     
  3. OP
    Nawaz SouthSudan

    Nawaz SouthSudan New Member

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    Your Mercedes:
    ML63 2007 6.2 AMG

    @alexanderfoti - Thank you. Now - is there a way to test the starter for a fault like worn brushes, partially overheated windings?

    New generation mechanics - replace modules... not repair.

    Point 2 is very silly of MB to do... - I have the "devil's chariot" - an X6 4.4 Twin turbo - with similar setup... causes no end of problems with the battery...
     
  4. alexanderfoti

    alexanderfoti Moderator

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    Your Mercedes:
    W221 S65 AMG - W204 C63 AMG + Various other MB's
    The one way pulley is there to save the life of the belt, as the alternator has a lot of inertia with rapid speed changes.
    The active charging management is all in the quest for better fuel economy!

    There may be, but I do not know how. This would be the domain of starter repair places , or motor rewinders. You could extrapolate based on the current draw, but I don't know what the right value would be.

    Have you checked grounding straps aren't missing etc?
     
    Last edited: Aug 20, 2018
  5. OP
    Nawaz SouthSudan

    Nawaz SouthSudan New Member

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    Your Mercedes:
    ML63 2007 6.2 AMG
    Will check the ground straps... and current draw.
     
    alexanderfoti likes this.

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