Not recognizing external hard drive

Supplemental #2: Again not recognized. disconnected & connected a few times. I noticed that the leds showed reading/writing from External HD occurs, so I let it wait... and HOP(!) after a few minutes, it's there, and the backup continues smoothly.

Conclusions for External Hard Drive without addition power source:

• Make sure your External Drive is Formatted in FAT32.
• Connect it to the main USB ports (e.g. back of mac mini; not to the keyboard USB hub);
• If it used to work, connect, verify that reading/writing occurs from/to HD
  (e.g. blinking-running dots in WD Passport)

  if not, and just in standby mode, disconnect and try to connect again;

• Then, wait a few minutes.

  if failes, diconnect and try again.

I hope this solves the issue for some of us.

Good luck,
Tal

I had the same problem with the Time Machine partition, after installing Tuxera. Tried to make the repair of the disk in disk utility and it wasn't succesful, said it couldn't repair.

Any way, after that my time machine partition appeared on Finder!

Thanks Mac, bad experience with tuxera solved by apple!

Hopefully this can help someone who lands here...

We were editing videos and had a lot of footage on our 1 TB Go-Flex Seagate hard drive. Part way through the project after unplugging the hard drive and taking a few days break, my macbook pro would not recognize the hard drive anymore. Not in Desktop or Finder. I could see it on the HD Disk Utility but it was not picking it up when we attached the USB.

On a chance, I downloaded NTFS paragon software, installed it and restarted. Now it is working perfectly again.

I think we got NTFS paragon software as a trial with the hard drive and when it must have expired quietly. So be sure to check this. There is a free trial on the website so you won't be out any money if it turns out not to be your issue.

this happened to my Toshiba imation drive as well. So glad I found this thread. I was patient. Waited almost 30 minutes and it showed up mounted in Finder. However it had turned "Read Only" so I had to repair it in disk utility and now its fine.

Mine came with a trial program that runs NTFS. When It ran out it no longer showed up on the desktop, so I got Tuxera; worked for me.

Thank you so much for posting the suggestion to swap out power supplies. I had to remove my old MacBook hard drive and connect it to my iMac to access a backup on an external drive. When I connected the MacBook drive to one of several identical external power supplies it just sat there 'ticking' and wasn't seen by the iMac. Reading your post gave me the 'what the heck' idea to swap the power supply and that did the trick.

First post ever of any kind. I spent most of the day trying to solve this for Lacie 1tb external drive, and then stumbled upon this solution for Lacie external hd users. http://claytron.com/blog/lacie-big-disk-fail.

Bottom line, when I switch the power supply for my Lacie to the one that came with my Seagate, issue dissappeared. Annoying that this isnt better communicated by Lacie

My problem is from the other end. I have a toshiba 1tb external hard drive on which I back up my Toshiba lap top. This morning when I tried to do this both USB ports on the laptop died. Thats a very short explanation for what has taken some time to establish. To get them working again I have to reboot the laptop & then I can use my wireless mouse & keyboard etc. Attach the harddrive again everything dies.

Now the point that got me to this board is that I gave my hard drive to a colleague to copy some files (which he did) but he runs a bloody mac! Has his mac killed my hard drive & done something that somehow means when it plugs into my laptop it kills that too?

Wow, who'd a thunk it? Replacing the power brick on my Vantec NexStar hard drive dock solved my issue.

The old power brick used to work. But after a hiatus of a couple of months I tried it and it didn't work for 3.5" drives in the dock, just 2.5" drives.

So I had a power supply from an old external drive and that worked! Presto!

I'm amazed.

For those who are using a mac with a Western Digital external drive and is having issues with recognizing the external drive, a simple solution could be unplugging the power from the external and the USB cable from the computer...wait 5 min and plug everything back in. This solution fixed my problem. Initially, neither my computer or disk utility recognized the external.

If you're restoring from an external drive because you got a new computer or did a clean install, you must set up the new installation with the same system user name and password as your time machine user and password. I believe this may also be case sensitive.

Do not format your backup drive as case sensitive.

Same issues here.

2010 Imac, running Seagate Free Agent 1TB through Firewire, format is Mac OS Extended (Journaled).

15 days ago it stopped backing up. I ran disk utility and it stated it needed repair. I ran repair and it states Error: Disk Utility cant repair this disk reformat you disk, and restore your backed up files.

Fortunately I also use an off site back up of my files, I would like to know what happened. I will try to reformat the disc and reinstall.

I'm not sure this is the same problem but it seems to be related. My flash drive stopped working in any of the USB ports of my Mac Pro. I don't get the error message when pulling it out but I do get the low power error message when plugging into the keyboard's USB port. I tried with two other flash drives (Kingston, Memorex, Sandisk) and the same thing. All of them work on the iMacs, G5s, and other Power Macs around the office. I tried an WD external 1 TB drive and exactly the same thing. Otherwise the computer works fine, with the exception that the Bluetooth stops working periodically and then comes back just as unexpectedly. Any ideas?