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  1. #1
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    Z370-E CPU Fan Error

    Unfortunately I suspect my CPU Fan Header has just failed on my Z370-e...

    I have been using my computer consistently for the last 2months (& have not opened/modified it since I put it together). I was browsing the web and suddenly I noticed my CPU fans stopped spinning. I thought it was strange, but I was just web browsing and CPU temps were only 30-35degC, so I thought maybe the CPU just cool enough. Note that it's not like they were overloaded; no intense processes were going on. The computer continued to operate normally for several (>10mins). Then I needed to restart cpu for unrelated software reasons.

    However on bootup, the CPU-Fans would not spin. The BIOS reports an instant "CPU FAN ERROR", and entering into the bios details it clearly does not see the CPU-FAN. I'm guessing the Bios prevents CPU from booting if the CPU-FANS are not working.

    I am fairly certain it is truly the Motherboard because of the following:
    1) Tried a separate known-working fan, and it would not spin on CPU_FAN_HEADER
    2) Applied 12V to my CPU fans separately outside of case, they worked fine
    3) 4x Case Fans continue to spin and operate normally.
    3) Since CPU continued to work normally, unlikely the power supply is dead.
    4) Used Multimeter to measure the +12V on CPU_FAN_HEADER, and it was unstable/jumping. (I'm an Electrical Engineer)
    5) Confirmed no "Cable-Shorts" in the FAN cables

    #6) (EDIT3): CPU FAN OPT, the fan header just a few mm away, spins the fan just fine. However it does not clear the CPU FAN alarm in bios.

    #7) (Edit4): So this is very interesting... In the BIOS if I toggle the CPU_FAN to DC mode the fan spins up. However PWM Mode seems to not work AT ALL anymore. My Fan is a PWM Noctua NHD-15S, and the PWM mode worked fine for the last 2+ months no problem...


    My speccs:
    i7-8700k
    Gtx 1080Ti
    Seasonic 850W PowerSupply
    (EDIT): I was on Bios 0419. That was updated when that bios update was released ~1-1.5 months ago
    (EDIT2): Adding Fans - dual fan Noctua NHD-15s
    Last edited by ernest.eedesign; 12-12-2017 at 08:10 AM.

  2. #2
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    1 Last update before I give up for the night...

    PWM mode works correctly on the CPU_OPT header, however the standard CPU_FAN header shuts completely off when I enable PWM or AUTO modes. DC Mode seems to work just fine...

    It's almost as if the PWM functionality related to the CPU_FAN header completely died randomly (literally no setting change, no cable issue, no short, etc. Just died).


    Note that all this testing is entirely in BIOS.



    My last thought is to update bios to 0430, but I've been using 0419 without problems for >2months so I find that unlikely.
    Last edited by ernest.eedesign; 12-12-2017 at 09:24 AM.

  3. #3
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    FYI I made this video demonstrating the problem. It is 100% that the PWM functionality on CPU_FAN header is broken. When connected to CPU_OPT (literally right next to it) it works properly and is controlled by the same BIOS settings.

    Board was sent in for RMA... Let's hope it's not another RMA nightmare story.

    https://www.youtube.com/watch?v=FWV1vwE5gV0

  4. #4
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    Z370-E returned from RMA, will test tonight... Paperwork says they replaced the CPU socket (which I wouldn't be surprised if I nicked it ONLY WHILE PACKAGING FOR RMA while trying to put on the CPU socket cover...).


    I seriously doubt my issue was repaired... I bought a replacement Z370-E to use to hold me over with the same fans/CPU/PSU/etc. and have had no issues.... As a hardware electrical engineer, I'm highly suspicious it's fixed since it was only the PWM functionality on the CPU_FAN header that was not operating at all.



    What do I do if the RMA did not repair the issue?

  5. #5
    Tech Marketing Manager HQ Array Raja@ASUS's Avatar
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    If the RMA is unsucessful, there is a customer loyalty rep in North America that can help.

  6. #6
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    Quote Originally Posted by Raja@ASUS View Post
    If the RMA is unsucessful, there is a customer loyalty rep in North America that can help.
    I misunderstood the paperwork; they replaced the CPU socket but it seems they still could not fix the issue (as I expected; I probably knicked a pin while packaging up for RMA...).

    They shipped me a new Motherboard; so customer complaint "resolved". Thanks Asus! Temporary board sent back for return, and Windows OEM license xferred to my new Mobo..



    @Raja a few recommendations from a fellow Engineer if you wish to pass onto your ME/EE team

    1) Since I knicked the CPU socket on RMA packaging, I'll tell you where I went wrong when re-packaging the MOBO for RMA... The CPU-Socket Cover (black plastic cover) needs to be installed on the OUTSIDE of the CPU-lever bracket. Intuitively this was backwards to my expectation (as the CPU gets installed first, INSIDE, and then the CPU-lever bracket holds it down). The CPU cover has extruding plastic towards the CPU socket. If you try to put the cover on first and THEN try to hold it down the the CPU-Lever backet as I did you run risk of the extruding plastic touching the cpu socket. May sound stupid to someone who does this frequently, but I doubt I'm the first to make this dumb mistake (and how often is the CUSTOMER putting ON the cpu socket as opposed to removing). In my industry we call this Poke-Yoke design (idiot proof so even if someone temporarily tries to do it wrong they can't break it). I think it could be easily fixed with some ME tweaks to the CPU socket cover (e.g. the extruding cpu-socket side plastic removed). Just a recommendation


    2) The PWM functionality did truly fail on my board I returned after 2months of use; I confirmed no short and same fans/cpu/etc. are still working fine. I had 2x NHD-15 PWM wired through Noctua's fan 2:1 PWM fan cable (only routes the sense signal from 1 fan, but both fans are driven by PWM/PWR/GND) signals. Since DC mode worked fine I know it's the PWM functionality that failed. Not that it's my design but I would check that the PWM control pin drive strength is enough to handle that perhaps its driven by a transistor or something. The Connector specs could certainly handle the current/Power of both fans, but since it's the PWM control that failed I'd start there. I'm now using both CPU fans split between CPU_FAN and CPU_OPT headers since I suspect there is a hardware flaw that maybe needs some investigation.

    Not sure how much you guys investigate your field failures.


    Thanks Asus! RMA experience successful.

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