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Terminal 30 Undervoltage

Discussion in 'Electrics, Vacuum, Ignition and ECU' started by ifti, Aug 10, 2018.

  1. ifti

    ifti Member

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    Joined:
    Apr 16, 2014
    Your Mercedes:
    E-Class E220 2008
    Hi

    we have a w211 2008 e-class 45k miles.
    its showing an undervoltage error when i did an odb2 scan
    when i checked it for live data its showing 4.67v
    Driver, Passenger and Rear Sam are all under 5V.
    The Battery is only a year old and the car is only driven on weekends for about 10 miles.

    Any idea what i could check for.

    thanks in advance,
     
  2. grahamcol

    grahamcol Senior Member

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    Joined:
    Jan 12, 2009
    Location:
    West Midlands
    Your Mercedes:
    2001 SLK230, 2000 C280 V6
    Welcome.
    From your usage profile I'd say the car doesn't get enough use to keep the battery properly charged. Lots of us use a CTEK charger - they're very good and ideal for keeping the battery charged and in good condition.
     
  3. OP
    ifti

    ifti Member

    Messages:
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    Joined:
    Apr 16, 2014
    Your Mercedes:
    E-Class E220 2008
    battery was 11.8v when off and was charging ok, went to +14V when car was running,

    i cant communicate via odb to clear any errors when trying.

    i also have a windscreen washer error, DTC9020 lead has a short to ground or open circuit,
    i feel this may be a old code when we replaced the windscreen washer motor but am not sure.

    also can i remove the negative terminal and put the battery on charge, while secured in the car ?

    thanks again for your replies
     
  4. grahamcol

    grahamcol Senior Member

    Messages:
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    118
    Joined:
    Jan 12, 2009
    Location:
    West Midlands
    Your Mercedes:
    2001 SLK230, 2000 C280 V6
    Can't comment about your other codes but the CTEK is marketed for safe connection without disconnecting a battery terminal. I've been doing this for years with my Mercs and have never had a problem. Your car is later than mine and so has more electronics, however I don't think you'd have a problem - see what others here say.
     
  5. Steve@Avantgarde

    Steve@Avantgarde Forum Supporter Authorised Forum Supporter

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    Joined:
    Dec 8, 2009
    Location:
    Bristol/Somerset
    Your Mercedes:
    Mercedes-Benz C32AMG, SL55AMG, C320CDI Sport Edition Estate and SLR McLaren Coupe Roadster.
    Carry out a load, hold and crank capacity check of the battery. You will need a proper midtronics tester or equivalent to do this.
     

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