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[Resolved] My P85 has developed the milling noise and Tesla won't fix it.

Discussion in 'Model S' started by kenkamm, Sep 16, 2015.

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  1. kennybobby

    kennybobby Member

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    from Amped Realtor:
    "Four distinct problems in the drive units that keeps recurring even with remanufactured units - drone above 65 MPH, clunking noise, milling noise, and high-pitched electrical buzz under 25 MPH."
     
  2. Soolim

    Soolim Member

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    In an industrial environment where large induction motors are control by VFD, the high frequency generated by the VFD (harmonic distortion) induce a high voltage over the bearing and cause the bearing pitting and ultimately to fail. The known solutions to such problem are:
    1. use motor with a ceramic ball bearing.
    2. Grounding brushing on the motor bearing body to shunt the induced voltage to shaft.

    Background information if bearing noise is to be blamed.
    For typical industrial motor (for north america), the fundamental frequency is 60Hz. The motor speed is a function of the frequency applied, varying the fundamental frequency from 0 to 60Hz changes the motor speed. In generating the varying frequency by VFD, AC is first converted to DC by converter, and then the DC bus voltage is pulse width modulated to produce the varying frequency by an inverter. The inverter chops the DC voltage to produce the fundamental frequency but also generates harmonic frequency of several orders, 3rd to 50th. The harmonic frequency is the culprit in this induced voltage across the bearing if not properly grounded.

    Tesla VFD DC bus voltage is supplied by the car battery, therefore no need for the AC-DC converter, but the DC-AC inverter is required. Tesla drive motor runs at tens of thousand RPM, much higher than the typical 1800RPM of industrial motors, therefore the fundamental frequency of the VFD is already much higher than 60Hz. I don't have the exact number, but the theory is valid. This higher frequency VFD also generates higher harmonics, aggravating the bearing arcing problem.
    Others claim that the whinning noise is from the gears, please refer to their post for further insight. The exact cause of the noise is yet to be determined.
     
  3. kenkamm

    kenkamm Member

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    Fascinating stuff!
     
  4. mknox

    mknox Well-Known Member

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    I was told I would have to wait until they got a replacement DU in, and that it wasn't a really high priority. That was some time ago, so maybe the delay I'm seeing has to do with this on-site fix and getting the necessary parts/training. They said it was only "cosmetic" hence the lower priority, and I am okay with that as long as it's true and I'm not a DU failure waiting to happen.
     
  5. apacheguy

    apacheguy S Sig #255

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    Wasn't there something about a "new and better fix" (along with the embargo) on the way a month or so ago? Sounds like a reengineered component that will likely require a new DU install. But who knows maybe they can retrofit.
     
  6. yobigd20

    yobigd20 Well-Known Member

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    in my opinion, Elon's answers were total BS to quell the media. I bet it's more like "several cars" needed a bracket and a shim while 99% of the other cars exhibiting this issue are the bearing problem that Elon conveniently left out of describing to the media. It seems to me to be more of a fleetwide design defect, which is pretty catastrophic if the media gets wind that the situation had not been improved and if anything it's is getting worse and much more widespread as the community starts racking up the mileage and the bearings start to get more worn.
     
  7. AmpedRealtor

    AmpedRealtor Well-Known Member

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    Totally agree. I was trying to be diplomatic earlier, but you nailed it.
     
  8. hpham007

    hpham007 Banned

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    This is no way scientific but it seems like the majority of the owners are seeing DU replacements at the 2 year mark. While I'm not sure if its a fleet wide issue, if 2014 models start showings signs of DU failures next year, then that would be more evidence supporting your view. A bigger question is if this issue has been resolved for the Model X and are we confident that DU failures will not occur in the SUV?
     
  9. mknox

    mknox Well-Known Member

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    Annual for me, but I do drive about twice the "average" (24,000 miles a year). Hence my guess is that it's mileage-based.
     
  10. Vitold

    Vitold Active Member

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    Interesting read. From what I find this is not a new phenomenon and there are ways to mitigate it. Specs of VFD motors I could find on line list bearing life (L10) of 20000 hours. 20k hours is 700k miles at average speed of 35mph.

    Considering that VFD motors can be maintenance free for a long time it's possible that certain revisions (models?) of Tesla's motors may have issues with shaft grounding which is why some cars had noise fixed - by replacing worn-out parts - only to reappear since cause of the issue (bad shaft grounding) has not been addressed.
     
  11. kort677

    kort677 Banned

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    agreed, there has been a very high rate of failures, if I recall even one of the auto mags had it happen to them of their long term test "ride".
     
  12. hpham007

    hpham007 Banned

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    I just found this interesting video. It shows that Tesla do use ceramic bearings. Would that eliminate the electrolysis theory? Or are the bearing races still metal and experiencing electrolysis which would wear away the ceramic balls?
     
  13. kennybobby

    kennybobby Member

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    Great find on the SKF video and the ceramic bearings, thanks for sharing.
     
  14. Soolim

    Soolim Member

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    Yes, I pointed out in my post that ceramic ball bearing is one solution to mitigate VFD harmonic current induced arc pitting (also called electrolytic corrosion), and confirmed by the SKF video. Bearing race electrolytic corrosion is unlikely due to the gap created by the ceramic balls.
    Strangely, starting at around 5:00 of the video I could hear some whinning:frown: Not sure where the video recording mic is picking that sound.
     
  15. Vitold

    Vitold Active Member

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    We are back to square one. Since electrolytic corrosion is not affecting bearings or races something else is causing the noise.

    - - - Updated - - -

    70D uses Tesla's newest motors and it would be interesting to know if 'milling noise' is affecting 70D owners as well.
     
  16. cab

    cab Member

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    For those of us considering pre-owned Teslas this is all doubling concerning and that concern is further driven by the lack of any third party repair shops, parts availability, shop manuals, general "repair cost" info, etc. For me when considering these kinds of cars used (as when I bought a pre-owned M5 w/o a warranty) it all comes down to assessing my exposure/risk. The Model S is a black hole in this regard right now.

    1. Can the drive unit be repaired vs. replaced? Don't know, but presumably based on what we have all read.
    2. How long does repair/replacement take in labor hours? Don't know.
    3. What does the repair consist of? Don't know.
    4. What parts are needed and what do they cost? Is there a core charge? Don't know.
    5. How likely is it that this repair will be needed during my ownership? Don't know, but it sure seems like an awful lot of folks are encountering it.
    6. Are special tools required to perform the repair or is there any kind of special procedure needed afterward to calibrate or set up something?

    My M5 was a repair magnet, but there was only ONE item that was generally a pain if if it broke - the transmission - as there were no repair parts available (i.e. meaning you had to replace the entire thing). Fortunately, the incidence of complete transmission failure was very low so that risk was minimal. Everything else (and there was a lot of it), I was able to address myself.

    While a pre-owned car might still have this under warranty for the next few years, it will, minimally, become an issue for resale if these questions aren't answered...
     
  17. davidc18

    davidc18 Active Member

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    I'm not sure how to categorize the noise, but our 70D has been into the service center twice for noise from the front engine. The first time after the test ride they said the noise was not normal and would order a replacement, which they planned on doing during the 5000 mile tire rotation. At just over 5000 miles, with the noise much louder, they decided it was now normal. Close to 7000 miles and the noise is now audible at all speeds and is loud enough to be heard at 75+ mph. I'm now waiting to see just how long I can stand the noise before trying with the SC again. Perhaps the unit will just fail and remove any doubts.

     
  18. AmpedRealtor

    AmpedRealtor Well-Known Member

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    So it would appear that an entirely new motor design is also exhibiting noise issues. Did someone at Tesla order their engineering degree from Fiji or something?
     
  19. Tupelo

    Tupelo Member

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    My '14 S85 with 18,500 miles has developed the noise. It sounds like an electrical "buzzing" noise when power is applied during acceleration, and rises as the speed increases. It's getting louder and is occurring now over a longer power/speed band. It goes silent when I ease up on the accelerator (0 kw applied) or regen engages. I'll take it to my SC and see what they advise. Sadly, I feel like I drive around now in a broken car and it really diminishes the enjoyment I've experienced being a Model S owner.
     
  20. Vitold

    Vitold Active Member

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    This could mean that it's not a motor but gearbox that is making the noise.
     

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