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Thread: Low voltage

  1. #1
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    Default Low voltage

    Alrighty guys this morning when I started my car it sounded like the battery was low, OBC says 11.86 with the car off. Started it and it went up to 12.2, driving it only goes up to 14.02 max and jumps around between 13.5-14.01. During idle it drops way back to 11.8. If it was charging at 13.5-14.0 why would the battery be so low... diode drain also?

    Sounds like an alternater to me but wanted to double check here before I start swapping out parts to find the fix.

    Edit: The battery is only 1.5 years old

    TIA
    Last edited by 632 Regal; 04-25-2007 at 02:42 PM.
    95 E34 530I V2.37
    ===========
    Those who make peaceful revolution impossible will make violent revolution inevitable.

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  2. #2
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    Default

    the 530 has the Bosch 140 amp unit right?
    95 E34 530I V2.37
    ===========
    Those who make peaceful revolution impossible will make violent revolution inevitable.

    John F. Kennedy

  3. #3
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    Default

    The OBC gives you voltage? Please share how.

    If it goes up to 14+ volts while driving doesn't that mean the alternator is OK?
    How old is your battery? Maybe it won't take a charge.

  4. #4
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    it used to always run high 13-14.5 now 11 at an idle means its not charging. I need my car so I ordered an alternater.

    OBC press 1000 and 10 at the same time (test) then click the '1' 9 times and it should show voltage

    Quote Originally Posted by kick7ca
    The OBC gives you voltage? Please share how.

    If it goes up to 14+ volts while driving doesn't that mean the alternator is OK?
    How old is your battery? Maybe it won't take a charge.
    95 E34 530I V2.37
    ===========
    Those who make peaceful revolution impossible will make violent revolution inevitable.

    John F. Kennedy

  5. #5
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    Default

    UPDATE: Just took the car out and it healed itself, lowest voltage at idle in drive is 12.51 does not drop below. when driving its fluxuating between 13.71 and 14.02

    WTF is going on here???
    95 E34 530I V2.37
    ===========
    Those who make peaceful revolution impossible will make violent revolution inevitable.

    John F. Kennedy

  6. #6
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    Default

    Alternator schmalternator, change the regulator only. It has the brushes and all and is easy to change, might be able to do it on the car.
    "The gas pedal wouldn't go to the floor if it weren't meant to be there"

  7. #7
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    not on MY car, I'll change the whole thing and hope to get another 200k outta it. With my luck ill get the wrong regulator, or ill bust something and then be stranded with just the 8er...driving it around these roads wouldnt be a recommended option.
    Quote Originally Posted by Ross
    Alternator schmalternator, change the regulator only. It has the brushes and all and is easy to change, might be able to do it on the car.
    95 E34 530I V2.37
    ===========
    Those who make peaceful revolution impossible will make violent revolution inevitable.

    John F. Kennedy

  8. #8
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    Does the engine need to come out to do the alternator? What about the brushes? I seem to recall reading that it might be possible to do it without removing lifting the engine, but I haven't heard of too many people doing this themselves.

    Edit: on an M60.
    '94 540I 6spd/205000 miles

  9. #9
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    It is quite easy to change the regulator, unless you have a V12 engine where the space is limited. Here you can see how to do
    http://bmwe32.masscom.net/sean750/Vo...eRegulator.htm

    @632 Regal

    Just wait and see how that develops. The regulator regulates it, so if the battery is full, and there is no much need for electric power, it will be less.

    I also have sometimes less than 12 V on the OBC, sometimes 13.2-13.5 V.

    Basically, - depending on the quality of ther multimeter you are using-, the OBC will always show between 0.2-0.5 V less than you measure with a DMM directly under the hood. That is the loss thru the wires and the connections up to the OBC.

    I tested that with 3 different DMM to eliminate wrong measurements and the accuracy of the DMM, there I found the difference of between 0.2-0.5 V.

    A cheap DMM for 5 $ is in my opinion useless anyway to measure .xx voltages.
    It will tell you 12 V for exa,ple, but if 12.1 or 12.5 V is correct, that is doubtful.

    So measure directly! OBC is just an indication.

  10. #10
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    Quote Originally Posted by 632 Regal
    it used to always run high 13-14.5 now 11 at an idle means its not charging. I need my car so I ordered an alternater.

    OBC press 1000 and 10 at the same time (test) then click the '1' 9 times and it should show voltage
    I think if the OBC is locked it won't show that...forgot how to unlock OBC though

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