External Hard drives are used to save, back up or transfer many important files because they have large capacity and stable performance. However, external hard drives can inevitably stop working in a sudden.

Some common symptoms of a failing external hard drive on Mac:

  1. The hard drive does not show up on Mac, especially not in the Finder or in the Disk Utility.
  2. Files are missing or changing sizes.
  3. The hard drive keeps connecting and disconnecting from the computer.
  4. The error message “The disk you inserted was not readable by this computer” pops up when the hard drive is attached.
  5. The hard drive is grey-out in the Disk Utility and cannot be mounted.

The signs are warning you that your external hard drive is probably suffering either logical corruption or physical damages, preventing the disk from working properly. Even worse, your valuable information on the disk may become corrupted or completely inaccessible soon.

Are there any ways that can save your external hard drive and the information on it? Stay tuned. This post will focus on how to fix a faulty external hard drive on Mac platform without data loss.

First, change USB port or/and USB cable

A malfunctioning USB port or USB cable will result in unstable connection between the external hard drives and the Mac computer. To know if it is the connectivity that causes a not working drive, reattach the drive through a different port or/and cable. If USB port and USB cable are functioning well, go ahead to check the disk status in the Disk Utility to know if it is fixable.

Then, check disk status in the Disk Utility

Disk Utility is a pre-installed application on Mac for managing internal and external disks. All detected disks, by default, will be automatically mounted and listed in the left window of Disk Utility. If you don't see the external hard drive in the list, click on the “View” at the top menu bar (where Apple logo is) and select “Show All Devices”. It should show up all external devices that macOS has detected. If your external hard drive still doesn't show up in the list, unfortunately, the drive must be damaged physically on its USB port, platter, magnetic head or other physical components. You cannot fix it by yourself so that you have to hand it over to a professional local data recovery service for restoring data and purchase a new one for later use.

If the disk is detected by macOS and shows up in the Disk Utility, it is time for you to get hands on fixing the troubled external hard drive.

Mount the hard drive yourself

If the drive is grey in the left panel, did you force the drive to mount manually? You can select the external hard drive and click on “Mount” to make the computer pick up the drive. Alternatively, you can also right-click the external disk in the Disk Utility and select “Mount” option from the menu text. If it doesn't work, run First Aid to fix the not working external hard drive.

Run First Aid to fix the hard drive

Like Windows has chkdsk command, macOS has its native approach to check and fix disk problems too. But it is achieved through a utility called First Aid not command lines. All disk related activities are performed in Disk Utility, so is First Aid. You can select the external hard drive, click on “First Aid” and then “Run” button. Even though I always tell people don't expect too much gain from running First Aid, it does work if your disk is slightly off track. If fixing this faulty external hard drive is beyond First Aid's capabilities, formatting the drive will be your last choice to make the drive readable and writable again.

Format the hard drive

You are probably looking for solutions for repairing the faulty external hard drive without formatting, because you know formatting will delete all saved important files on the external hard drive. It will cause serious data loss if you don't have adequate backups. Nevertheless, if you have gone through all methods above and come to this far, you should be convinced that your external hard drive is severely logically messed up. Only assigning a new file system to it can make it workable again.

Don't be too concerned. Data recovery software like iBoysoft Data Recovery for Mac can easily restore your important information from the external hard drive. It is a trustworthy program which can

  • Restore pictures, documents, videos, emails, and lots of common file types from hard drives, SD cards, USB flash drives.
  • Recover data from a disk that is formatted, corrupted, unmountable, or unreadable.
  • Recover data from unbootable Macs.
  • Recover data from lost or deleted APFS volumes.
  • Support APFS, encrypted APFS, HFS, HFS+, FAT, and exFAT file systems.
  • It is fully friendly to latest macOS and earlier OS X (down to OS X 10.7).
How to Fix a Faulty Seagate, WD or any other External Hard Drive on Mac? 2

After having recovered the badly needed files, go ahead to format the disk. To perform the formatting, you need to utilize the “Erase” feature in Mac's Disk Utility. When you are selecting the format, FAT or ExFAT is universal format you need to choose if you are going to use the external hard drive across Windows and macOS.

A final note

I always recommend people buy hard drives from reliable manufacturers liks Seagate, Western Digital, Samsung or Toshiba, because you can turn to their support if your external hard drive starts to fail. Their support team can give you professional advice as I do here too.

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