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Thread: Could a blown PS pump cause the alternator not to charge at low rpms

  1. #1
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    Default Could a blown PS pump cause the alternator not to charge at low rpms

    So my PS pump blew this week. Im at school and haven't had a chance to replace it. Im going to this weekend when i go home. But now my car doesnt like to even turn over if it idles for to long. My lights go dim, my cd player stop workin, and then my CEL, ABS and SRS light come on, and then the starter doesnt even click. Can this all be cause my low battery voltage. When im crusing at 3k rpm or so everything goes back to normal. Im just wonderin the PS pump is the root of my problems or if i should look elsewhere while im workin on the car.

  2. #2
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    Default

    replace the battery.

    go for an optima red top, the one i got isnt supposed to fit in my car, but i made if fit anyway, and its much better.

  3. #3
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    Default

    sounds like the alternator isnt charging, does the belt look good?
    95 E34 530I V2.37
    ===========
    Those who make peaceful revolution impossible will make violent revolution inevitable.

    John F. Kennedy

  4. #4
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    Quote Originally Posted by 632 Regal
    sounds like the alternator isnt charging, does the belt look good?
    Could the PS pump be drawing too much from the engine in idle therefore causing not enough power to the alternator?
    I wonder cause sometimes when my idle is crappy the lights dim too.

  5. #5
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    Default If you have an OBC, ...

    take a look at this thread.

    Javier

    Edit: Not sure about 520, but if the belt for PS pump and alternator is the same, yes the belt may be slipping due to a defective pump, causing the alternator to run very slow. Revving up, should relieve the situation.
    Last edited by Javier; 06-17-2006 at 04:37 AM.

  6. #6
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    Quote Originally Posted by BillionPa
    replace the battery.

    go for an optima red top, the one i got isnt supposed to fit in my car, but i made if fit anyway, and its much better.
    If the engine is running, the power comes from the alternator and not the battery. So why should he change the battery?
    Testing of battery and alternator is anyway easily done.

  7. #7
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    Default

    Javier, is that information available for the 5-Series?
    Josh



    1990 BMW 525iA
    2000 Toyota Corolla CE
    2007 Toyota Echo

  8. #8
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    Quote Originally Posted by shogun
    If the engine is running, the power comes from the alternator and not the battery. So why should he change the battery?
    Testing of battery and alternator is anyway easily done.
    So when lights dim when your idle drops to like 300 rpm it's normal?

  9. #9
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    Default

    @Josh: it is the same for the E34 and E32, because both use the OBC IV, if they have one, otherwise they have a clock installed.

    @Morgenster: 300 RPM is much too low, even my V12 engines run higher at about 550-600 RPM.
    At 300 RPM the alternator might not produce enough to supply the complete central chassis electronics with enough power and then the battery is drained too.
    The bst is to use a good DMM and test
    battery with no key in ignition
    battery with ignition set to position 2
    lowest point durung engine cranking
    at idle
    at around 1.500 RPM

    Just today I use my unlocked PC while diring to check the voltage during driving: it was never below 13 V, usually around 13.4.-13.6 V.

  10. #10
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    Default

    i am saying replace the batt, because it sounds like the battery isnt charging properly at low currents, and not holding its charge.

    check the alternator voltage when the car is running, it should be over 13.8

    if its lower, then something is wrong with the alternator, possibly the voltage regulator.

    if its at least there or higher, the battery is fried.

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