2018 Mac Mini - monitor problems

For what it is worth, I am using a LG 27UK850-W 27" 4K UHD monitor and connecting to the 2018 Mini with the HDMI/HDMI cable that came with the LG. When I check the (running) connection with System Information.app, I get:

 Graphics/Displays:

LG HDR 4K:

  Resolution: 3840 x 2160 (2160p 4K UHD - Ultra High Definition)

  UI Looks like: 1920 x 1080 @ 60 Hz

  Framebuffer Depth: 30-Bit Color (ARGB2101010)

  Main Display: Yes

  Mirror: Off

  Online: Yes

  Rotation: Supported

  Adapter Type: DVI or HDMI

  Automatically Adjust Brightness: No

  Adapter Firmware Version: 2.0a

Changing to a USB-C/USB-C cable gives me the same UI Looks Like resolution. Also,I don't repurpose any of the other monitor connections for charging or whatnot. So far, everything in my Sept 3, 2019 workaround seems to work--tap the shift key twice and immediate wake-y wake-y.

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In my case this is Mac Mini 2018 i7 and Eizo S1921 monitor. Disabling File Vault, neither upgrade to OS X 10.4.6 helped anything. I have 10 days left to return Mac Mini getting money back. It the problem is not solved during that time - e.g. by Catalina release - I will send Mac Mini 2018 back to the shop for get my money back.

The Mojave 10.14.6 update appears to have resolved the issue for me. Before the update, I sometimes (but not always) had to press the power button on the Mac Mini (i7 16G 1TB) a couple of times (one press for 1 second & release, then a quick second press & release) before the Mac would recognize the monitor (an LG 34" HDMI connected). After the 10.14.6 update I haven't had to go through that rigamarole again. The Mac is recognizing it every time now as it should.

Same issue here.....

The machine boots normally, but the screen is always blank....not even Apple logo.

I have to unplug the HDMI cable and plug it back in to the Mac Mini for the screen to appear.

As long as I don't shutdown the Mac, I'm able to restart and wake up from sleep no problems.

As soon as I shutdown and try to boot from cold, the display is black.

Very annoying.

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OK something weird just happened....

I grabbed another monitor Dell E2219HN FHD with HDMI input and plugged it into my Mac Mini and problem still occurred - black screen. While the screen was black, I tapped the power button a few times (between 2-6 times) and the screen came on.

To test it fully, I then did a full shutdown. Powered the Mac Mini back up and low and behold the screen turns on normally. Done this about 6 times and it turns on every single time.

I also tested it with sleep and restart - all good.

Fingers crossed this continues to work and is not just a temporary fix.

Interestingly I was having this problem until I realised if I switch on my Mac Mini before turning on my monitor the mac mini refuses to detect the screen unless I power cycle it. However if I make sure my monitor is on (showing no signal or similar and not in standby) before I turn on the mac mini when its powered on screen works straight away. I've been shutting my mac down and turning on daily and the screen has consistently been detected. I'm using Thunderbolt 3 connections to a 4k screen

I admit it shouldn't be this way and the mini should detect the screen even after its been switched on but at least it works as intended! Running 10.14.6 Mojave. Hope this helps someone!

Incredible. After installing Mojave 10.14.6 my screen and my Mac mini started to work perfectly. Everything was perfect until last week when I updated to Mojave 10.14.6 b My problems with my LG restarted again. However, this time the problem is different, my 2018 Mac mini detects the screen and it works right but after 20 minutes the screen flickers. My the only way to solve it has beeb to connect the display to the Mac mini with a HDMI USB-C adapter. Then the problem has been solved.

My recommendation buy an adapter and connect the display through the USB-C connection.

I hope it helps

I do not understand! After you installed Mojave 10.14.6, everything started to work. Then after you updated to Mojave 10.14.6 B, same problems came back, but changed out connections, problem solved. What is Mojave 10.14.6 B? If it is beta program, you on your own!

Australia calling... I've had multiple supplemental updates to Mojave. for security fixes (variously named supplemental update and supplemental update 2).

Needless to say, the monitor not waking from sleep issue persists...

I am a long term mini i7 user. I too had many problems with two monitors, FileVault, external drives.

i brought the mini in to Apple. They replaced the motherboard. Monitor problems went away... and I was happy for about 3 months.

but

i updated to 10.14.6 rev b. Ever since then, one or the other screen blinks out for a few seconds ‘ or one screen gets a blue tinge.

‘sometimes my tb3 external hard drives do not appear. The root cause? Bad things happen when I put big load on the mini, like]I gotta runninghuge Database’s where temp rises to 100 degrees c and the fan jumps to 4000 rpm. Soon after that, bad things start to happen.

i suspect that this is both a hardware and software issue. In other words, the mini i7 gets overloaded and drops communication with various items on the bus.

until Apple announces a replacement plan for the mini, better fan etc., or comes up with a reliable software solution, the solution is to switch to a iMac or new Pro, and retire the mini to perhaps an email server or some other lightweight duty

like a music box.

I suspect it was too much to ask to have a i7 six coreloaded with lots of monitors and external drives and running big computational loads. . The thermal issues are somehow

causing the mini to drop external load.

$1700 invested for the mini i7 512 gb. $10,000 wasted personal time fooling around with this box. Not a good strategy.

i just bought a dell i9 for $1400. Same or better specs than the mini. Hugely better thermal capacity in a desktop tower.

i will keep the mini as a 32 bit machine to I can run legacy Mac software. 10.15 64 but rules are simply dumb.

all my scanner drivers are e2 bit and no, Lexmark and hp are not likely to update their drivers on 4 year old $5000

off8ce mfc... they would rather you buy new $5000 machines.

apple is doing no one any favors by killing 32 bit. If windows 10 64 bit can run 32 bit programs, there is no reason

Catalina can’t... apple can leave in some legacy code do that all our scanners will continue to work

and, good news, with the dell, I don’t have to put up with parallels updates and license issues with multiple boxes.

You can avoid most of the thermal issues by installing the utility "Turbo Boost Switcher for OSX" and disabling turbo boost. My 2018 i7 Mac mini now runs nearly 30C cooler (60C vs 87C peaking at 100C) when only using 17% of the CPU cores as per the Intel Power utility. So, yes, the 2018 Mac mini has thermal issues too. Overall, it's been a rather disappointing experience compared to the Mac minis from previous years. My next machine will be an Intel NUC running FreeBSD.

I installed Catalina and now I’m back to square one. Mojave 10.14.6 fixed my problem with no video on startup, at least on HDMI. still broken on USB-C to DisplayPort, but at least it was working with HDMI. I loaded Catalina and now I’m back to blindly typing my password on boot. Also, any pre-boot menus are a problem such as trying to get into recovery mode and the menu to boot from another drive.

Why couldn’t they just incorporate the 10.14.6 fixes into Catalina? They broke it all over again.

I guess I have to make ANOTHER support call tonight!

Just loaded Catalina..... was a tense moment, but after a good nail biting hour of watching the entire installation, the display finally loaded up on my FHD work monitor....no need to unplug/replug HDMI cable to get a video signal.

Did the shut down, restart and sleep a few times to fully test the Mac Mini.

Am quite happy its been working solidly for the last week on 10.14.6......and now its working with Catalina 10.15.

Are you guys running 4k monitors or FHD??

This is limited to 4K. I can drag out a dusty old square HP 1080p monitor and it works fine.

I was on the phone with a senior advisor today. I have a case going back months for this. 10.14.6 fixed mine for HDMI, but not USB-C to DisplayPort. I was happy with that because at least it was working. Catalina broke it. Now it's even worse. HDMI is totally shot. DisplayPort works once it's booted. Now I have a new problem where sometimes the monitor won't see a signal when I wake the Mac. I know the machine is awake because my USB hub light comes on.

Advisor screen shared my iPhone while I videoed it not working. He sent some notes to the engineers and he's supposed to call me Wednesday.

Royal PITA. Seems like they're dragging this out until the warranty expires in January. I'm not paying for Apple Care just so they can keep stalling.

Using FHD here. An LG HDR WFHD 34-inch ultra wide, HDMI connected to be specific.

Still running Mojave 10.14.6 without experiencing any monitor recognition issues. Going to wait a while to install Catalina.