2018 Mac Mini - monitor problems

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??

I guess I got my hopes up too quickly with my supposed fix. I went to turn it on today and got slapped with the dreaded blank screen again. This time the unplug/ replug HDMI trick doesn't work anymore.

I'm counting my apples this is a hardware issue since it just happened out of the blue without doing any software updates or doing anything different.

I've wasted days trying different combinations of things to fix it. Am getting tired of how unreliable this product is. This one is definately going back to Apple.

I tried an HDMI > VGA adapter that I use for my Raspberry Pi3 - it's worse! At bootup, the screen displays wavy purple lines, and eventually settles on a black screen. Re-plugging the video cable has no effect (unlike with the USB-C > VGA adapter). Worth a shot, but no cigar.

den2020 just a word of advise, don't waste your time going to any service centre. They will be clueless as to how to help and offer to ship off Mac Mini for further repair. And Mac were well aware that a clean install of the OS was going to be of no help as well. And putting you threw it was a waste of your time. But it did make it appear that they were trying. I got my 2018 Mac Mini way back in May 2019 and immediately had problems with monitor loosing connection on reboot and cold starts. Went threw all the trouble of replacing what was a new monitor at the time. No luck. Traded out Mac Mini for a different one as well as upgraded to better i-5 as well. No luck. After dealing with support for some time and doing re-install of OS as well as them taking logs to send off I discovered thousands of posts from others with same problem. Going back to 2018. I have read it all and heard all Apple has to say and it is all different. First it was file vaults fault, turn it off. But mine was never on. CABLES, tried them all. No luck. Then for me, I installed Beta version of now available Catalina and solved monitor problems instantly. I posted about this at time. As I still followed posts I seen that an update to Mojave that came out at the time fixed problems for many people as well. All was well for awhile on Beta until Firefox would only crash and would never work. So as I heard all was well after Mojave update I reverted back to Mojave and had no trouble at all this time. But now I see that some have upgraded to Catalina and have still had trouble. No idea. Only know that it worked for me and it continued to work when I reverted back to updated Mojave. Still working. Anything Apple is saying at this point is pure bull. They are clueless. But I do suggest trying to update to new Catalina which you will now find running updates as it's been available for a little while now. Not the beta which is better for you. Won't hurt to try and you can always revert back easy enough. Hope this helps fill in some of the blanks.

I have a 2018 Mac mini, connected through Thunderbolt 3 to a LG32UL950 monitor. I used to have the same problems, described in this thread, but I turned off FileVault, updated to macOS Catalina, including the update, that came today /15OCT2019/ and also updated the firmware of the monitor through Onscreen Control and so far my Mac wakes up the monitor every time I start it. I hope this information will be useful to someone and also hope that some time in the future we will be able to use FileVault.

I have exactly the same symptoms.

When the screen goes blank, I need to plug it into a 1080P monitor first, then plug it back into my 4k LG for screen to come back on. This only happens when using a HDMI->HDMI cable.

I'm beginning to think it's a HDMI port problem.

So I've decided to move away from HDMI altogether and use USB-C.

I've been using a USB-C->DP cable for the last few days and so far no issues.

I also bought a USB-C->USB-C cable which also has been working without issues.

I have ordered a USB-C->HDMI cable and will try that soon.

hi guys, I followed this topic even before I got mac mini this July. I was hoping I will not be affected as I just plugged monitor and power supply cable - no possible interference with external HD, no usbc hub etc.

Always used HDMI-HDMI under Mojave and it was causing issues on LG 27UK650. I always had to turn the monitor on when I start mini to see the login screen. Never ever seen apple logo with progress bar.

HDMI-HDMI suddenly stopped working when upgrading to Catalina last week. Just like most of you. I even thought mini simply died (wish it did and have my money back).

I called Apple, got case assigned. Spent 5 hrs on phone with Senior last Fri. I followed some troubleshooting recommendations, ie. removed some files from Libraries/Preferences folder, clearing VRAM, starting in recovery mode. Nothing had helped so I was asked to wipe all data from SSD and install Catalina again. I did so, nothing helped.

I was asked to try another cable so I got TB3- HDMI cable, it is working fine now but I only have 30 Hz refresh rate and I literally hate to use mini now because I feel like we are still in '90.

They are supposed to call me today. I sent them 250 MB of log from switching between cables as requested by Senior.

I was also told they cannot access this forum (sic!) and dont recognize the scale of that issue.

PLEASE, CALL APPLE AND OPEN CASE FOR THAT!

This is ongoing issue from the very first day the mini released and no one is gonna say this is because of monitor/ cable - they worked (almost) fine for me before Catalina upgrade so why cant they work fine after?

Isotovi, make sure your cable is rated to run 4k@60hz. There's plenty of fakes on eBay. This is the only cable I have yet to try on my MM2018. All the other USB-C display cables I've tried work great so far.

huh, spent 40 EUR on that one, thought it will work fine. Funny story is what Apple told me when I asked the question while resolving screen not working issue - you only get 30 Hz from USBc cable. Use DP. I will push back on that now.

So you are saying I should try better cable and it will give me 60Hz being still USBC to HDMI?

UPDATE: LG WFHD 34” ultra wide connected HDMI to HDMI using the cable that came with the monitor continues working on 2018 Mac Mini i7/16GB/1TB (FileVault NOT in use) without any issues since upgrade to Mojave 10.14.6. External drive works fine too. Can’t afford risk of Catalina upgrade interrupting workflow, so going to wait a while before doing that.

I did the update to Catalina on both machines , Nothing noticeable on the Mac mini fix or changed . The iMac went through a totally different setup process when I down loaded the patch and its problems seem to be fixed .

upgrading ram to the Mac mini this evening so will see if it boots to HDMI after I am finished .

I haven't tried the adaptors, but keep in mind that you are introducing an unknown variable into the picture.

This is important if you want to test something and trying to isolate an issue.

Personally I would stay clear of adaptors and buy a dedicated cable that's rated for your monitor resolution and refresh rate. It's also cleaner. I have a million cables running under my desk and adding an extra adaptor means another thing I need to try and hide ;).

got USBC-DP cable, 60Hz is now working. Improvement over 30Hz for USBC-HDMI i have been using last days.

BUT - the automatic date/ time is not working when I use any USBC cable for monitor (HDMI and DP). I noted that before - HDMI-HDMI allowed the location services and automatic time zone but not USBC.

I would appreciate if you check that on your mini.

It is not desperately needed, just annoying the Night Mode/ Night Shift will never turn on automatically as the location cannot be detected (needed for sunset/sunrise I guess). Many thanks!

Same issues here with a 2018 Mac Mini bought last month (was Mojave, now Catalina). My monitor is an LG-27UD88Q. I've tried HDMI, USB-C, DisplayPort and also USB-C to Displayport cables, none of them seem to make a difference.

Problem seems to be worse when the machine is powered-off rather than just going to sleep, although the sleep issue seems to be getting worse.

If I plug in an old monitor via HDMI, it seems to be recognised every time and I can then switch back to my new monitor. But its frustrating beyond belief!

And yes, the monitor works 100% of the time when connected to my MacBook.

I have seen a few posts where they say Apple does not see these posts. Well that is wrong as I was just e-mailed that my last post was deleted because Apple didn't like me speaking bad of them. Point being they do monitor these posts for those who feel they don't. So they are well aware of what is happening. Speak bad of Apple and they delete you. So please watch what you say.