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Thread: Charging System Faulty?

  1. #1
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    Charging System Faulty?

    A little more than a week ago, while driving, numerous dash lights came on and the car went into limp shifting mode. I stopped and tried to restart. Result was no crank. Fortunately this happened at an Indy shop that works BMWs. They replaced the battery and all was good until today when the same thing happened; 20 miles from home this time.

    I canít find my voltmeter 😒. So, I obviously need to go buy another to see if Iím getting an acceptable rate of charge. And go from there...

    Here is a pict of the dash today.

    thanks in advance for sharing your insight/experience

    todd
    04 325ci convertible
    Attached Images Attached Images

  2. #2
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    More info,

    Shortly after the dash lights and limp home mode; the gauges, windows, radio stopped working, the window and the HVAC display was very dim.

    Thanks

    todd
    04 325ci convertible

  3. #3
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    Google “BMW E46 hidden OBC functions.” Test #9 shows the voltage as seen by the engine computer (DME in BMWeze). Also, perform the gauge cluster test to make sure all indicators are working properly. I’m betting the alternator is the culprit. Be advised that BMW sourced alternators from Bosch (yay!) and Valeo ( ), a French company. They are not interchangeable!! How to tell which is in your car? Remove the air cleaner box plans the upper intake hose. Use a flashlight and a mirror to read the label at the back. The label will tell you the alternator’s brand and the capacity (in amps). If it’s a Bosch you can replace the voltage regulator (VR) easily. The Bosch VR is about $50 from fcpeuro, a great online vendor. A Valeo VR is more expensive.
    How many miles on the car? If the car is approaching 200k miles it’s probably time for a rebuilt alternator. If the car has a Bosch alternator make sure the “new” rebuilt alternator was rebuilt by Bosch and comes in a black box.

  4. #4
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    Thanks Marco. Nice to know about the hidden test functions!

    I’m nearly finished with a 2 amp battery slow charge and I will check this out tomorrow.
    I figure the alternator is going to be the culprit on this 150k car.

    todd
    04 325ci convertible

  5. #5
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    Quote Originally Posted by Crosst View Post
    Thanks Marco. Nice to know about the hidden test functions!

    I’m nearly finished with a 2 amp battery slow charge and I will check this out tomorrow.
    I figure the alternator is going to be the culprit on this 150k car.

    todd
    04 325ci convertible

    I call alternator went bed. But i dont know how you lasted a week on just a battery. You will need to find out if you got a Bosch or a Valeo Alternator and most likely its 120 amp. RealOem will not tell you which one you got but you can tell by the pulley and it should be written on the back of the voltage regulator. You will need to put in the same one it was in there.

    good luck

  6. #6
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    Battery charged up and shows 12.8v
    With car idling, or at ~2k rpm, with or without load, I have 13.8v or 13.9v
    That seems fine.

    I’ll check the ground strap tomorrow

    thanks
    todd
    04 325ci

  7. #7
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    The readings with the engine running are a tad low, but likely acceptable. Your car may have a parasitic electrical drain. This happens when an electric or electrical component draws power when it’s not supposed to when the car is off. Is the FSR original? Does the heating/ac fan run erratically?
    Last edited by MarcoZandrini; 01-08-2018 at 08:53 AM.

  8. #8
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    Hadn’t thought about the FSR as a possible problem (I’m still new to these cars). The HVAC fan has shown no strange behavior. That’s an inexpensive part to proactively replace. I’ll check on the R&R of it.

    Thanks
    todd
    04 325ci convertible

  9. #9
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    I'm with Marco, parasitic battery drain.
    Not a BMW, but electrical principles are the same:https://www.youtube.com/watch?v=QRso1A0VScw
    "It's not how you race your car, it's how you stand by your car, you better learn that".
    Edited version

  10. #10
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    12.2v on the battery this morning. Definitely looks like the battery is draining. The drive in to work showed 13.9v - 14.0v for the 10 mile drive.

    I have an FSR on order [cheap item].

    Is it possible that my 2 week old battery is defective, and not holding a charge?

    ———

    Update, on my way home from work today, using the OBD test feature, the voltage reading started at 14.0v and then dropped to and stayed at about 12.0v after a couple of miles.

    Thinking VR as a possibility now.


    thanks
    todd
    04 325ci convertible
    Last edited by Crosst; 01-09-2018 at 06:51 PM. Reason: Updated

  11. #11
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    The dealer thinks I have a Bosch alternator based on my VIN. To confirm, can you tell from this picture if Bosch or Valeo?

    thanks
    todd
    04 325ci convertible

    0F1073B7-3C22-4604-8792-5655E4A53BB2.jpg0F1073B7-3C22-4604-8792-5655E4A53BB2.jpg

  12. #12
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    The only way to positively tell which alternator is in the car is to remove the air filter box and the upper inner hose. Then, use a flashlight and a mirror to read the label at the rear of the alternator. The label will tell you the alternator’s capacity, also. It’s either 90 amps or 120 amps.

  13. #13
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    Quote Originally Posted by MarcoZandrini View Post
    The only way to positively tell which alternator is in the car is to remove the air filter box and the upper inner hose. Then, use a flashlight and a mirror to read the label at the rear of the alternator. The label will tell you the alternator’s capacity, also. It’s either 90 amps or 120 amps.
    No one mentioned here that the alternator is putting out. And if they did, they didn't question the draw...if in fact there is one. A qualified meter can identify current-draw. A charge current should show between 13 and 15 volts indicating the alternator is producing. A worn and or faulty 'regulator' does frequently fail.....'Regulators' are the only part replacement PART.. attached..to the alternator usually (2-3 SCREW BOLTS) to the alternator...an easy replacement item....Please look into this.
    Last edited by Eaglesail; 01-16-2018 at 05:44 PM.

  14. #14
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    Ref post #10; I found that my alternator was putting out ~13.9v for a few miles and then it would drop to 12v and stay there.... So, I took it to a shop and they confirmed this. I had them replace the alternator and now all seems well. Didn't realistically see me having time to do it myself in the near term.

    thanks
    todd
    04 325ci convertible

  15. #15
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    Sometimes the regulator can be equal in cost to an entire unit, so why bother?
    Total replacement with a quality unit is the smart choice.
    "It's not how you race your car, it's how you stand by your car, you better learn that".
    Edited version

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