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Mac Mini 2018 USB-C port issues

S

strawbale

macrumors 6502
Original poster
Mar 25, 2011
412
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French Pyrenees
Been using one of these ports (with a USB-C to micro-USB-B cable to my WD ext HDs) for years to do weekly backups.
Suddenly, now, these mains-powered ext disks are not any more 'seen' (not in Finder nor in Disk Utility) by any of the Mac Mini 4 ports.
However, when using the same cable with the USB 2.0 port of my wired keyboard (that is plugged in the USB-A ports of the Mac Mini), it DOES work. And testing the Mini's USB-C ports with a USB-stick all 4 ports work fine too.

So it seems these 4 ports, suddenly, all still work for data transfer unless that's an ext HDD, even though these ext HDs are mains-powered?

Any ideas are most welcome!

PS: Another issue seems to show up at the same time: when logging in I cannot type in the password box at first, after a seconds a window comes up saying that it's looking for a bluetooth keyboard (which I don't have), the window then disappears, and only then I can type my password 🤷‍♂️
 
So, you are saying that the external HD won't mount when plugged directly into a USB port on your mini-- but, the HD will mount (allowing data transfers) when plugged into a USB port on your wired USB keyboard?
 
DeltaMac said:
So, you are saying that the external HD won't mount when plugged directly into a USB port on your mini-- but, the HD will mount (allowing data transfers) when plugged into a USB port on your wired USB keyboard?
Click to expand...
Yes, but using different Mac Mini USB ports:
plugged directly NOT working with any of the Mac Mini's four USB-C ports; plugging indirectly (via my wired keyboard) using the Mac Mini's USB-A ports it DOES work.
PS: I didn't test directly into the Mac Mini's USB-A ports (as then I'd have to unplug my wired keyboard), but I assume that'd work too.
 
I've tested with two different cables, the ones that have always been working.

Does an external HD, even a mains-powered one, need a powered connection with the Mac Mini?
 
The USB port on your wired USB keyboard is not powered...

Looking back at your first post... Seems like you don't have ANY USB at first (you couldn't type on your USB keyboard, then get the "searching for keyboard" (your Mac would then be searching for ANY keyboard, it's normal for it to search for a bluetooth, when no USB keyboard is detected, even if you have never used a bluetooth keyboard. That's normal when no other keyboard is detected.
So, your Mac mini is simply slow to boot, and slow to detect (and connect to) USB devices. Something is not working correctly.
What OTHER devices do you normally have connected to your mini, on ANY port, including any external USB hubs, other external networks/Ethernet cables?
What macOS system are you using now? Have you updated to the current macOS 26 (Tahoe)?
 
Thanks for getting back to me - much appreciated!

Normally only the monitor, through the hdmi port, and a printer, through the keyboard port (as it's I don't have a USB-C to USB-C printer cable). Occasionally a USB-stick.
It's my wife's computer, hardly used as she prefers her iPad mini. I use it occasionally as we've got MS Office on it (and not on my M1 Mc Mini).
Just tried printing with using the USB-A to USB-B printer cable and an USB-C to USB-C adapter in one of the Mac Mini's USB-C ports and that works fine, like the USB sticks did work fine in there.
I may have somewhere a powered as well as an non-powered USB-hub which I could try.
 
Update: with (mains-powered) ext HD connected to a Mac Mini's USB)C port via a mains-powered USB-hub it DOES work. (without the mains-power of that hub it does NOT work).
 
Might be helpful to run the built-in diagnostics on the mini.
This link should help with that...

Can you tell me what version of macOS is running? "About this Mac", in the top left corner of your screen, top item in the Apple menu will show the operating system version that you are using.
 
That links start internet recovery - is that what's needed?
I haven't chosen a language yet, like to know of I should proceed.
Googled what this does, so did proceed.

Diagnostics ran offline :
There may an issue with the Thunderbolt hardware
Disconnect external Thunderbolt devices and run the test again. If you get this message again click get started below

Which I did. Seems trying for ever to connect to start internet MacOS recovery (?)
Doesn't seem to be able to connect through wifi nor ethernet nor personal hotspot 🤷‍♂️

For the moment will (have to) continue to use one of the two workarounds: via wired keyboard or via mains-powered USB-hub
 
Last edited:
Diagnostics does not really use an internet connection (but may need to be connected, if possible)
I would suggest trying that diagnostics again, but no external devices, except your USB keyboard/mouse
Also, if you have one, a USB to ethernet adapter, plugged in to your internet. Your goal with this, is to get a results code, when the dignostics complete.
 
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I run two SSDs and had one powered spinner. The hard disc spinner was always having problems being seen. Always. Seven years of oh no it's not mounted again argh.
I retired it recently and the SSDs continue to be rock solid, never a single issue. Good riddance to the disc. I feel your pain OP. This model Mac is so finicky.
 
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DeltaMac said:
Diagnostics does not really use an internet connection (but may need to be connected, if possible)
I would suggest trying that diagnostics again, but no external devices, except your USB keyboard/mouse
Also, if you have one, a USB to ethernet adapter, plugged in to your internet. Your goal with this, is to get a results code, when the dignostics complete.
Click to expand...
The code I get after running diagnostics is NDT001:

"There may be an issue with the Thunderbolt hardware.
Disconnect external Thunderbolt devices and run the test again.

If this code appears again, further troubleshooting may be required. Contact Apple or take your computer to an AASP or Apple Store to learn which service and support options are available."

As the tests I've done since, see above, I think there is an interference between Bluetooth and the Thunderbolt/USB-C, because disable Bluetooth get rid of the issue. (not a solution for my backups, but good to know that works)

Then I read LionTeeth's post and tested, with Bluetooth on, an external SSD (T7) with its own, very short, cable: that worked fine!

As said before, ext HD via keyboard into Mac Mini's USB-A ports works, and ext HD via mains-powered USB in Mac Mini's TB/USB-C ports works too.

Conclusion:
There's 'only' an issue when, with Bluetooth ON, the ext HDs are plugged directly into the Mac Mini's TB/USB-C ports.
Unfortunately that's my user's case :(

A case of badly shielded cables in combination with Bluetooth?

Mac Mini (2018) - WiFi / Bluetooth problem - Apple Community

discussions.apple.com discussions.apple.com
eshop.macsales.com

Shielding Resolves USB 3.0 Conflict with Bluetooth

We set out to find a resolution to the problem - one that fixes things not just for the miniStack, but for all USB 3.0 drives used with a Mac mini.
eshop.macsales.com eshop.macsales.com

But why now, 7 years after having worked fine?
 
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