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MB Viano 2008 Not charging

Discussion in 'Electrics, Vacuum, Ignition and ECU' started by Freddyu, Feb 21, 2020.

  1. Freddyu

    Freddyu Member

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    Hi,
    i have a 2008 mb viano 2.2 4x4 that are not charging.. it has a 200A alternator.
    for some days ago i drove the car to the shops, all seems fine then, but on the way back i noticed that the red battery lamp was on, and as i assumed it was not charging.
    when i start the car the red battery indicator comes on after a few seconds

    I bought a new alternator, 200A and with the alternator it followed a test paper with the data from the test.
    we installed the alternator in the car and started the car.. no battery lamp.
    Jobb well done.. we think.. but he wanted to check with a multimeter, and it does not charge, no battery lamp, but we tried to turn on lights, fan etc.. voltage sinks.. then the red lamp gets on.
    we charged the car for an hour or so, then i started to drive home, using park lights and use a less as possible with current..
    my car has a spare battery that i have to charge my wheelchair from, it has a voltsensitive relay that i can activate with a switch.
    when i drove home, after 6-7 km the battery lamp came on, and i switched on the spare battery, the red battery lamp turned off, but after a while the red lamp was back.

    we are scratching our head now, what can be wrong. Can we messure the two signal cables that goes into the alternator to check if that is ok?

    any ideas?
     
  2. alexanderfoti

    alexanderfoti MBO Forum Supporter Authorised Forum Supporter

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    What voltage do you get with the engine running.

    Check for potential difference between engine and body of the vehicle in case one or more ground straps have disappeared
     
  3. OP
    Freddyu

    Freddyu Member

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    It has about 10V when i have only main battery that i have driven for a while without charging, when i switched on the second battery, it says 12.2V.
    Ground cable are OK, car starts with no problem.
    If there where a ground issue, should´t the car had problem running the starter?
     
  4. alexanderfoti

    alexanderfoti MBO Forum Supporter Authorised Forum Supporter

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    Yes, it would.

    I would check the continuity of the small wires going to the alternator. I Assume you have battery voltage at the large cable on the back
     
  5. OP
    Freddyu

    Freddyu Member

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    we used the multimeter from cars ground next to the fuse box and to the B+ on alternator and there is same voltage there as on the + in the fuse box.
    we have followed the thin cables from alternator and up to top of engine where it is combined with several cables, all seems fine.
     
  6. alexanderfoti

    alexanderfoti MBO Forum Supporter Authorised Forum Supporter

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    Have you actually checked the continuity between the wires though? I have seen many cables that look fine but are open circuit.
     
  7. OP
    Freddyu

    Freddyu Member

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    can we ohm the two thin cables? what should the readings be?
     
  8. OP
    Freddyu

    Freddyu Member

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    and, are there a fuse in the fusebox that are for these two thin cables., or are they connected into the control unit in the fuse box?
     
  9. Uncle Benz

    Uncle Benz Senior Member

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    It's definitely worth a close inspection of the large cable on the B+ terminal at the alternator all the way back to, if memory serves, the fuse box where it joins to a 225A fuse link. On vehicles with extra electrical equipment added (campers and the like) I have seen terminations overheated and burned where contact exists some of the time and drops out unexpectedly at others.
     
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  10. OP
    Freddyu

    Freddyu Member

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    hmm, but if that 225A fuse was burned, should there be same voltage on the B+ as the + in the fuse box?
     
  11. Uncle Benz

    Uncle Benz Senior Member

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    If it had blown, no, but I have seen the cable termination burned at the fuse giving an intermittent connection. It can meter ok for voltage, but when load is applied it can drop away.
     
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  12. OP
    Freddyu

    Freddyu Member

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    Thanks, i was out checking that fuse, and it seems all ok there, no signs of heat there
    [​IMG]
     
  13. OP
    Freddyu

    Freddyu Member

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  14. alexanderfoti

    alexanderfoti MBO Forum Supporter Authorised Forum Supporter

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  15. OP
    Freddyu

    Freddyu Member

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    Ok, is that unit the one that are controlling the charging? Tells the alternator to start charging?

    are there any way to force the charging to start?
     
  16. OP
    Freddyu

    Freddyu Member

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    tomorrow i am going to a guy that has equipment to read out errors from the car. hope i wind out whats the problem...
     

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