Mac Mini M4 and Apple Thunderbolt Display Problem on Sequoia 15.3

Question

Mac Mini M4 and Apple Thunderbolt Display Problem on Sequoia 15.3

Hi!

I have a Thunderbolt Display 27” (A1407) which I have always used with my Intel MacBook Pro 15-inch, 2017 (A1707) with a Thunderbolt 2 to Thunderbolt 3 (USB-C) adapter. It has always worked, almost flawlessly. Recently, I’ve bought a Mac Mini M4 (A3238) and I started using the Thunderbolt Display with my new Mac and it worked like a charm until I updated it to Sequoia 15.3.

Since then I can’t get it to recognize the display anymore. It still works with my MacBook Pro using the same cable and adapter, but there’s nothing I can do to make the Display work with my Mac Mini. I have even made a clean restore on the Mac Mini to no success.

I also can’t get anything to show up at my Thunderbolt/USB 4 Device Tree on System Information on my Mac Mini. When I connect a Thunderbolt 4 device on a TB 4 port on my Mac, they show up at the USB Device Tree instead.

Any idea what might be the problem?

Mac mini (M4)

Posted on Feb 18, 2025 10:18 AM

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Answer 1

samtenor

Level 4

2,074 points

Feb 18, 2025 06:58 PM in response to Marcelo Coutinho

A. Have you upgraded to Mac OS 15.3.1? -- Might worth a try.

B. Newer MacOS can be less-forgiving with fluctuation of the Thunderbolt Signal -- that can be related to old hardware (the infamous Octopus cable - from frayed/bend/old age of the TB1/2 connector). As result, the TB display became non-functional.

A quick workaround - a diagnostic step would be "buying a TB 1/2 cable - Apple made 0.5m and 2m" and the visual as below:

ps: I used MB Air in the picture - same principle to Mac Mini..

Best

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Answer 2

samtenor

Level 4

2,074 points

Feb 22, 2025 11:06 AM in response to Marcelo Coutinho

I am glad it was an easy fix for your situation.

From the years of playing with TB display, I found many "non-functional" TB displays (prior to M series Macs) due to the "Octopus" cable ~ most of them were over-stretch/bend while trying to connect the "power" and "TB connector." That's one of the reasons I was able to acquire 12+ TB display with little to no cost. It was fun project for me to open them and explore what the issue might be.

Some of the TB connector portion, can be freyed or "discolored" - and some fix required "tape it together."

Until, MacOS Sequoia - that MacOS 15 might have some build-in safe guard that any "drop" of signal - will result in non-function TB display. At least, the TB displays have extra TB port for this kind of quick fix.

Best

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Answer 3

Feb 19, 2025 06:58 AM in response to samtenor

I suppose that the cable is not the problem as it works with my MacBook Pro. The only thing I haven't tried yet is connecting the Mac mini directly to the extra thunderbolt port on the back of the Display. I've ordered a new TB Cable and I'll try it soon.

I'll post the results later.

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Answer 4

Feb 22, 2025 10:38 AM in response to samtenor

I've finally got a Thunderbolt 2 cable and as you suggested, it worked. As long as I use the extra thunderbolt port on the back of the display, it works fine.

For some reason, the built in thunderbolt cable doesn't work with the new macs/new MacOSs.

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