Studio Display with Mac mini. Please check if your display fans run constantly, even if both devices are in sleep mode - since macOS 15.4

[macOScurious]

The goal of this thread is to bring attention to an unexpected behavior, also known as bug, introduced with macOS 15.4. This bug seems to be widespread, but unfortunately most of the users will NOT recognize it.

The bug got confirmed by other users and so far there is no solution, not even a clean install.
The only workaround is to shut down the Mac mini for the night or time you are not using it.
Users still on macOS 15.3.2 and earlier confirmed there is no such behavior.

After the macOS update 15.4 the Apple Studio Display fans in sleep (standby) will run constantly (with a very short exception at the beginning) and draw more than 11 watts instead of approximately 0,4 watts.

Important:
All this is about Apple Studio Display (ASD) connected to a Mac mini NOT to a MacBook.
Also this is NOT about any fan noise or strange clicking sound out of the ASD
ASD firmware is 17.0, to check this, press and hold the Option key, then choose Apple menu -> System Information -> Displays
Connection is trough the original Thunderbolt cable delivered with the ASD.
There are no other external devices connected to the ASD USB ports.
macOS 15.4 up to 15.5

My setup, an ASD and a Mac mini M4 was put into operation December 2024. Everything was running smoothly. Right from the start I was watching the ASD and Mac mini power draw and how the display fans behave during sleep mode. So what I figured out and from now on will name expected behavior is as follows:
If you put the Mac mini to sleep, the Display turns black and after a couple of seconds the ASD fans stop running. A couple of minutes, can be 5, can be 20, the Mac mini is doing some background tasks, what is fine. During that time the Mac mini is calling home the Display stays dark and the fans are running. As soon as the Mac mini is done with whatever he needed to do in the background, the Display fans stop running. There are probably 3-6 background tasks per hour, each one lasting some short minutes.

Right after the macOS update 15.4 I recognized a totally different behavior of the Display fans and power draw. What I now will name UNEXPECTED behavior:
After putting the Mac mini and Display to sleep the Display fans stop running until the first background task of the Mac mini will take place. So far expected.
But now, with macOS 15.4 the Display fans keep running constantly, no matter if the Mac mini has finished his periodically background tasks. In fact the ASD fans will now run all the time until you shut down the Mac mini or pull out the thunderbolt cable connected to the display.

The reason for not recognizing this bug is because the ASD fans usually are totally silent. There is a quick and easy way to check if your fans are running. Just use one layer, as thin as possible, of e.g. a Kleenex tissue (1 by 3 inch) and put it on top of the display where the airflow is. Use a coin or small pice of tape to hold it in place. Not necessarily, but if you have, you can also use a voltmeter to check the power draw.

So, if you are using an Apple Studio Display with a Mac mini, please do yourself and all other users a favor and check your display fans. Every feedback with information about your setup is very much appreciated. We need to get rid of this bug.

Thanks for reading and thinking about this issue.

 

[russell_314]

The goal of this thread is to bring attention to an unexpected behavior, also known as bug,

Have you reported this to Apple in a bug report? Sometimes people overlook doing this.


I don’t have a Studio display (yet) but I hope this gets fixed for you soon!

 

[qap]

Yes I noticed it me too, and it’s a really annoying bug because it makes you spend money on electricity and wears out the internal fans of the Apple Studio Display.

I made a post on my blog with a workaround I found to turn off the display when the Mac goes to sleep: Apple Studio Display sleep issue

 

[steve217]

I've got the same setup as you - M4 Mini and ASD - and I'm not noticing this behavior with the fans.

I've put a piece of of tissue paper on the top of the monitor weighted down with a nail clipper. I'll keep an eye out but the most remarkable thing about this setup is the complete lack of fan noise.

If I didn't know better and you told me the M4 mini and the ASD didn't have fans, I'd believe you.

 

[macOScurious]

I've got the same setup as you - M4 Mini and ASD - and I'm not noticing this behavior with the fans.

I've put a piece of of tissue paper on the top of the monitor weighted down with a nail clipper. I'll keep an eye out but the most remarkable thing about this setup is the complete lack of fan noise.

If I didn't know better and you told me the M4 mini and the ASD didn't have fans, I'd believe you.

Thanks for your reply and information.

Just to clarify and to be sure your tissue is on the right place. The ASD airflow isn’t on the full length of the upper frame, even if the holes look like that.

Please make sure you place the loose end of the tissue approximately 15cm (just under 6 inch) from the left or right edge. That’s the spot air comes out.

Can you confirm the issue is at least “flying“ while Display is active?
What country are using the device? 110V or 220V (European) power supply devices?

 

[steve217]

Thanks for your reply and information.

Just to clarify and to be sure your tissue is on the right place. The ASD airflow isn’t on the full length of the upper frame, even if the holes look like that.

Please make sure you place the loose end of the tissue approximately 15cm (just under 6 inch) from the left or right edge. That’s the spot air comes out.

Can you confirm the issue is at least “flying“ while Display is active?
What country are using the device? 110V or 220V (European) power supply devices?

I moved the tissue with anchor to six inches from the edge of the display and yes, the tissue is showing that the fans are on even when the display is off and the Mac is asleep.

And I'm in the US (110v).

 

[macOScurious]

I moved the tissue with anchor to six inches from the edge of the display and yes, the tissue is showing that the fans are on even when the display is off and the Mac is asleep.

And I'm in the US (110v).

Thanks for taking the time to check again at the right spot, I honestly appreciate this.

Actually, even if this sounds strange, that’s good news. If your fans stay on all the time, not only for a couple of minutes while Mac doing background task, this would confirm the unexpected behavior.

So, these new (and older) M Macs are build to stay on 24/7 year round, probably except for a long weekend or vacation time. To give you and others the math, if the Mac is used 8 hours a day and 14 hours in sleep we all waist and pay energy like this:
11,3 Watts (unexpected behavior) compared to 0,3 Watts (expected behavior) is 11 Watts x 14 hours x 365 days = 56 kWh (kilowatt-hours) x all users with this bug.

Also this is totally unnecessarily wear and tear for the Studio Display fans.
Numbers above will double if the setup is used in a privat home where you are not busy with your Mac all day.

We would need to get more attention to this thread from more users to proof and confirm this unexpected behavior. This is not a missing emoji or minor glitch, this is serious. But, compared to a glitch or even a missing emoji, this is not so obvious.

Right now Apple Support does not confirm this as an official unexpected behavior because there are not so many people opening a case (ticket). IMHO the only reason for this is because it's not recognized by users. Also Apple support is getting mixed up with other and older strange behavior that has nothing to do with this new (since macOS 15.4) bug. It seems to be very important to separate this issue from already known other things about the ASD you will find online.

Thanks for your interest and please consider opening a case and / or talk to other users.