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Thread: intermittently charging issue

  1. #1
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    intermittently charging issue

    .
    Last edited by kutsyy; 01-27-2019 at 01:21 AM.

  2. #2
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    Your alternator only charges when the car is coasting. Yes, I know, that's stupid.

    Does your oil level sender work? Can you check the oil via the I-drive? (Yes, I know that sounds unrelated, but it's not)

    Read this:

    https://www.roadandtrack.com/car-cul...ns-bmw-n63-v8/

    Never mind the charging -- you should really get rid of this car quickly, before you need an engine. The N63 generally doesn't last 100 k miles.

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, at an independent, formerly @ dealer
    BMWCCA 274412 SCCA 334928

  3. #3
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    The alternator (and the oil level sender) are controlled by the BSD bus circuit. This bus has a single wire connecting all 3 components: alternator, oil level sender, and DME.

    The alternator is not supposed to charge 13.9 V all the time, as you'll have seen in the R&T article. I'd GUESS that you have a BSD fault. Certainly, though, if the BSD circuit has an issue, OR if the alternator stops charging at any time without being commanded to stop charging, codes should be instantly set, which ISTA should find, and develop a test plan to diagnose.

    We had an identical car to yours in the shop, for a replacement engine, at 65 k miles. After the engine replacement, the car had a BSD code. ISTA said "Check these bolts", with a picture. Sure enough, one of the bolts, which ground the wiring rail on each cylinder head, was missing. That killed a ground inside the DME. However, the alternator continued charging...at 13.8 volts continually.

    Certainly, you should check the plug with the small single violet wire at the back of the alternator; make sure it's properly clipped on. Also, check the main big hot lead at the alternator, and at the starter, and at the B+ terminal underhood, Then also check both battery terminals, and the main engine ground wire. If any of these connections are loose, the battery won't get charged

    Do you have a red battery warning light when the alternator suddenly stops charging? What exactly is your signal that tells you the alternator's not charging?

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, at an independent, formerly @ dealer
    BMWCCA 274412 SCCA 334928

  4. #4
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    Follow the ISTA test plan.

    Bottom right: Calculate test plan. Your version is a little different from mine, but when the test plan comes up, double click on the top fault, follow through with test plan for that item.

    I'm wondering about the ZGM (central control module) lack of initialization, too.

    The car isn't finding the alternator. You're also not showing voltage at top right on terminals 15 and 30. What sort of weird clone ISTA are you using? Do you have a good stable power supply on the car while you're using ISTA? You need 13.4 to 14.9 volts!

    Have you checked whether the violet wire is firmly plugged into the alternator? (It can get to looking brown, after eight years living between cats and turbos)

    There are only 3 things on that wire: Alternator, DME, and oil level sender. You could check that wire for voltage, too; should be battery voltage,

    Have you had any work done to the engine, before this started?

    Any chance someone left a bolt loose on the wiring rail?
    Last edited by bmwdirtracer; 01-12-2019 at 08:22 PM.

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, at an independent, formerly @ dealer
    BMWCCA 274412 SCCA 334928

  5. #5
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    Do I call you Vadik, or Valim?

    There are three e-torx bolts on each head, holding down and grounding the wiring loom. Some damned dumb ass at BMW thought it would be okay for those to be crucial grounds. If just one of those bolts is left out, or loose, the damned DME gets fried.

    Now, this may not be the case, with your car...MAYBE the alternator plug is just loose?

    All that said, I really think that someone with an I.Q. equivalent to his shoe size designed the BSD circuit.

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, at an independent, formerly @ dealer
    BMWCCA 274412 SCCA 334928

  6. #6
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    Yep; those are the deadly bolts. I'm sure that BMW found this out quite by accident, after a number of DME's were toasted. Seriously, who would design something like that? Maybe they could have at least put yellow warning labels, like they do for everything else?

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, at an independent, formerly @ dealer
    BMWCCA 274412 SCCA 334928

  7. #7
    Join Date
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    As you'll see in the TIS link, these crucial bolts are on BOTH sides - look at the second picture in TIS.

    I know that wire LOOKS brown, but that's just because the violet color got burned away by the intense heat of having cats and turbos in the center of the "V".

    Any chance that someone has already been hunting for this problem? Because that break in the insulation sure looks like someone's been stabbing with a dull probe.

    Can you follow through the ISTA test plan for the 2 BSD codes?

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, at an independent, formerly @ dealer
    BMWCCA 274412 SCCA 334928

  8. #8
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    I will keep my fingers crossed for you, Vadik! We will be here to help, when you encounter further issues. I am happy that this problem seems to be solved.

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, at an independent, formerly @ dealer
    BMWCCA 274412 SCCA 334928

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