mac does not see external hard drive

I have done everything you suggested and nothing is working. My WD My Passport external HD worked last time I backed up my MacBook Air and now nothing shows up and disc utility can't find it. It just spins and spins. I have upgraded my Air to OS 10.11.3 El Capitan would that have caused it not to work?

I looked up this product. First, do you have the "for Mac" version that comes already formatted for Mac. Or did you get the "regular" version that targets Windows users (does not come formatted for Mac). If the latter, it probably came formatted using the NTFS disk format, so you would have to either reformat it for Mac (Erase it using Disk Utility) or install some type of third-party driver (OS X system extension) that allows your Mac to use NTFS. Does any of that sound familiar? If you installed a third-party driver, it may not be compatible with the latest version of OS X

Second, the product description says this external drive has encryption and password protection features. That implies another possible third-party system extension, or other type of software from WD. Again, it may not be compatible with latest version of OS X.

Did you install any software for using this external drive with Macs?

I have had this external HD for some time and have been using it on my Mac. I think it was for Mac. How can I reformat it if I can't get it to come up on my Mac? The Disk Utility can't find it. I don't remember install any software.

Try starting up in Safe Mode

Try safe mode if your Mac doesn't finish starting up - Apple Support

In Safe Mode, third-party system extensions are not loaded. If there's one interfering with access to the external drive, the drive may become accessible (or at least recognized in Disk Utility).

Other possibilities...

- The external drive enclosure is faulty.

- The hard drive mechanism is faulty.

- The USB cable is faulty. Try a different USB cable if you have one; if your external drive uses USB 3.0, use a cable that is rated for that speed (not an older one that is rated for USB 2.0).

- There is something wrong with the USB port. If your MacBook Air has more than one USB port, disconnect any other USB devices, and connect external drive to other USB ports. If you have not already, shut down (power off) the MacBook, then start up and connect the external drive by itself to a direct USB port.

Thanks for all your help, I appreciate it. I think I just need to go get a newer one. I have tried all the above and looked up solutions on their web site and nothing works.

Sometimes (maybe even often), with external drives, it's the enclosure that's built ultra-cheap and goes bad first, not the actual hard drive mechanism inside. If you're going to buy a new external drive, and this non-working one is passed any warranty or other coverage, you can disassemble it instead of just getting rid of it. I just saw an "empty" enclosure on sale at OWC for a ridiculous sale price. A USB 3.0 cable by itself (included) would cost more.

http://eshop.macsales.com/item/Seagate/SEXTDEXP2.5/

Use it to test your current hard drive mechanism in another enclosure. I'm assuming your external drive is the smaller "portable" type with a 2.5-inch hard drive inside (based on looking up "WD passport external drive"), NOT a larger "desktop" drive with a 3.5-inch hard drive inside.

I am not that tech savy. Thanks though.

I have the same problem. I turnout off my iMac, powered down all the external hard drives, unplugged everything, and moved to a new room. There I reassembled the setup without plugging in anything, then plugged in the power-strip, and turned it on which powered up all the drives. Then I turned on the iMac, and it only saw two of the drives: the Thunderbolt drives. All the other external drives were not see by the iMac. I repeated the process, and now only one of the Thunderbolt drives is seen.

Disk utility does not see those missing drives, except maybe under wrong names and with wrong information.

This is the biggest single problem I have had with my Macs: not seeing external hard drives. It is real voodoo. Should I sacrifice a chicken?

Since this problem occurred when you moved your system to a different location, you have to think the move is the cause. So, consider the things that are different now.

For example, how are your iMac and all of your peripherals connected to power? You seem to have a lot of external drives. And you said "power-strip" (singular). Are your iMac and all of your external drives plugged into the same power strip? There is a limit to how much current can pass through one wall power outlet. Some of your drives may not be getting enough power to operate properly; that can cause damage. Try getting another power strip. Connect that one to another power outlet (different location), and split your power cords between the two (or even three) power strips. Even if it worked before, electrical wiring is not always consistent everywhere in the building, and the total load capacity for a particular "circuit" may be different.

The setup was exactly the same at the new location as the old.

I discussed the problem with an Apple specialist, and also a tech support person from WD. I tried the FireWire hard disks on other Macs with success. We finally concluded that my iMac’s FireWire port was probably deceased.

I went to the closest Apple Store and purchased a Thunderbolt-to-Firewire adapter MD464LL/A. I plugged this in to the end of the small string of two Thunderbolt drives, and then downline from the adapter plugged in the string of the five FireWire drives. Very promptly the FireWire drives came up on the screen, working normally.

So it was apparently a hardware problem with the built-in FireWire port on the iMac. I am not sure that a dead port can be revivified, but at least we have a work-around.

Hi Kenichi.

I have been reading through this thread and I think my problem is ever so slightly different. I wonder if you have any wisdom to impart! I have a c2009 iMac and a Maxtor Onetouch III external hard drive with firewire cable. Previously my computer was running OS10.5 - 10.6, and the HD loaded fine when it was turned on (it plugs directly into the wall and has an on/off switch on its body).

Recently i upgraded the OS to 10.8.5, and when I connected and turned on the Maxtor HD, it did not automatically load. I opened Disk Utility, and the drive is there, but greyed out, as is the "mount" button. As you will see from the screengrab, it's telling me the SMART status is not supported. I never needed to check this before, so I'm not sure if it used to be supported and is no longer.

Is it an OS incompatibility? SInce upgrading my OS, I have had trouble with my original peripherals. My scanner will no longer connect (a known issue. I will have to get a newer model) and some gremlins in the printer when printing from certain applications. So maybe 10.8 just doesn't agree with all my bits and pieces. Do you know a way around this?

Thank you and good day,

Meiying

Hi Kenichi

I am having an issue reading my Seagate FreeAgent HDD 500GB too. I am using Macbook Pro OSX El Capitan 10:11:6. Here are the details.

1. The external hard disk is lighted when connected but does not appear in Finder or on the desktop. After a while, the light from the external hard disk is off when there is no activity on it.

2. I can find in Disk Utility but the left bar shows that the drive is greyed out. I also noticed that it says that there is 0kb available in the disk but I clearly remember that when I used the drive about 2 months ago, it was half utilised. Please see print screen below.

3. I tried "Mount" but no response.

4. I tried "First Aid" and my result is as follows.

5. I have tried the connecting wire on another similar Seagate external hard disk and it works.

6. The connecting point between the wire and the problematic hard disk is a bit shaky but is not loose. Is it a hardware issue?

Please advise what can I do to access to the important data in the external hard disk.

Thank you.

Maggie

Hi Kenichi Watanabe,

I have been reading through this thread and have a similar problem with my Samsung S2 portable hard drive.
I was cleaning my S2 portable from double files etc. Then I ejected the disk on the Mac Mini but didn't unplug the usb cable. Then because one program wasn't responding and neither would force quit, I had to turn of the mac mini by holding re on/off switch.
After restarting the Mac, it couldn't find my S2 portable anymore. I tried on two more macbooks air, all running Sierra or El Capitan. I did everything else mentioned in the thread to rule out other problems, but I'm sure it's the S2 portable itself.

When I run disk utility it does see the S2 portable in the list on the left but not a sub disk I could mount. Info window tells me all 640 GB are used while just 1/10th was in use.
Could you help with this problem as well? Thanks

ps. if u need screens shots let me know

best regards,

Shady

I ended up having to buy a new external HD. That worked. I had taken it into the Genius Guys at the Apple store and they said my old one wasn't compatible to the new iOS.

It was compatibale al along, it just got messed up for some reason, while the above happened!