Help: External WD disk unmounting

Discussion in 'Mac Accessories' started by grani13, Feb 26, 2017.

  1. grani13 macrumors member

    Mar 31, 2012

    I have a weird problem:

    I have an external WD (My book pro II, about 5 years old) that I have connected to my iMac. All of a sudden it started unmounting all of a sudden....I can switch it off, back on - it mounts again and after about 2-5 minutes it unmounts again....

    I have already tried changing the USB cable, using different ports - same thing.

    The interesting thing is: when I connect it to my old MBP, it works normally.

    Any idea what the reason could be and how to fix it?

  2. Fishrrman macrumors P6


    Feb 20, 2009
  3. satcomer macrumors 603


    Feb 19, 2008
    The Finger Lakes Region
    It might be the disk in the external is going to sleep and not waking up!
  4. grani13 thread starter macrumors member

    Mar 31, 2012
    Not that I would know. It was still working when I left for a vacation and didn't when I came back a week later (nobody touched anything in the mean time)
    --- Post Merged, Feb 26, 2017 ---
    I think the light indicator on the HD does mean "standby/sleep", however the disk goes into that mode while doing time machine back ups, accessing/copying files etc....
  5. grani13 thread starter macrumors member

    Mar 31, 2012
    So the situation is still unresolved - HD constantly disconnecting on the iMac, and perfectly stable and working on the MBP.

    Interesting detail that I just realised now - as soon as the external HD is connected, the trackpad on the MBP starts acting up (almost impossible to navigate, cursor jumping erratically etc...). When I unplug the HD, it's normal again.

    So - is that some kind of electrical problem? Any further ideas on what I could look out for to fix it? Or should I rathe consider writing it off?
  6. Fishrrman macrumors P6


    Feb 20, 2009

    Get what you need from the drive, then reinitialize it.

    If it still won't work with the iMac and/or the MBPro, retire it.
  7. ZapNZs macrumors 68020


    Jan 23, 2017
    I agree attempting a full wipe/reinitializing as Fishrrman suggested is a good idea. If that does not work and you wish to troubleshoot further, you could run a diagnostic App on the hard drive that pulls SMART parameters, and this is capable of checking for several types of electrical issues that could cause this issue. It can also look at the overall health of the drive to tell you how much estimated life remains. It sounds like there may be an issue with the power supply to the drive, since it is having issues on both of your computers. And while that issue might be related to the enclosure, because the drive is at the five year old mark, its service life is probably nearing the end (so replacing both versus one would arguably be ideal.)

    Are you having any issues with other USB devices on the iMac or the MacBook Pro, or is this the only USB device that is having issues?

    If you decide to replace the drive, purchasing the drive and enclosure separately will usually yield a faster, more reliable, and more economical solution than most pre-packaged external drives + enclosures do.

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6 February 26, 2017