2018 Mac Mini - monitor problems

I'm in the [cold start - no signal - entering power saving mode] camp.

Taking a look at the install.log file, I can see this started for me after installing macOS 10.14.5. Before getting a 4K monitor I was using a Samsung TV (UE43J5570SU), which is Full HD but not 4K. I did Xcode development without any issues on macOS 10.14.1, 10.14.2 and 10.14.4 using this setup (since November of last year).

After installing macOS 10.14.5 last week, I noticed the issue with the Samsung TV. I thought it was a TV issue and forgot about it, since I was getting an LG 4K monitor anyway (27UK850-W). This works beautifully with the official HDMI cable provided by LG in the box. But it has the issue, just like I had started having with the Samsung TV after 10.14.5. I couldn't test the 4K monitor in a previous masOS version to compare.

I also have to power off a couple of times until the "forgotten password" appears and then restart. After one restart, the Apple logo showed a blinking red-filled box around it, as the progress bar was increasing. That was weird, as in some kind of synching issue.

Hope this helps the engineers, the new 10.14.6 beta looks promising for some people.

I sold mine today and returned to my old 2012 Mac Mini. That machine have no issues at all. Crackeling audio problems and sync issues with monitors is just to much for me.

I noticed the monitor problems with the 2018 Mac Minis at launch in the store I work in. We sell those. I thought that would have been solved by now. I have no hope at all that this will ever be solved.

I received from eBay USB-C to HDMI (male) adapter. I'm testing it almost one week and till now I have no problem. I'm curious what will be with the next OS update. Now I'm running at 10.14.5.

Monitor LG W2600H DVI to HDMI cable connected to MacMini 2018 via USB-C to HDMI. As I mentioned here, the DVI to HDMI-HDMI(MacMini) causing problems.

Good luck to every one. Hope that apple will solve it.

I hope that continues to work for you BranoB.

Just an FYI I have had great luck with Cable Matters cables, especially Ethernet cables. You get them on Amazon, they are fairly/low priced and come with a lifetime guarantee. The Ethernet cables have metal jacketed connector which stands up to a lot of plugging and unplugging.

I ordered new Cable Matter HDMI cables which I am pretty sure will be better than the cheap ones that came with my older ViewSonic monitor. I would prefer to use the HDMI port as I have a number of peripherals that will I would like to leave plugged into the four USB-C ports.

I'm running a 2018 Mac mini (Mojave 10.14.5) and every time it restarts I have to unplug the HDMI cord from the LG monitor - count to 5 and plug back in. I know it's on because when I tap the keys or mouse I can hear the bing from the speaker. Works fine after that even from sleep mode. Only on restart does the monitor show no signal. Thought it was because I bought refurbished. This Mac mini replaced my 2012 version which had no monitor problems. File Vault is off for me and doesn't make a difference. Any other ideas?

Now that I have joined the beta club and installed the new OS Catalina, I have not had a problem with my monitor not connecting on reboot and as well on cold start. Updating to Catalina has fixed all monitor problems for me. This after me having to return my 2018 Mac Mini and getting another only to have same problem. Monitor loosing signal. A lot!!!!!!!!!

I hope this will help others if they want to get beta Catalina and upgrade. Everything has run well for me on Catalina. No bugs to report, other than 32 bit apps are no longer supported. I can live with that now that my monitor connects how it should. Thanks for your time.

Desronto and Ravenx619, thank you for the encouraging reports and link to the Beta program. Since this 2018 Mac mini is used for business I am concerned about using the Catalina beta but being a very much a geek when I was younger I will probably end up downloading and installing the Beta after creating a Carbon Copy Clone of my Mojave install as there are two programs I need on occasion that are 32 bit. I feel really bad for those who returned their Mac minis thinking that they were experiencing hardware issues but can understand why they did it.

I just bought the Imac Pro instead. Guess what. No problems at all with the same Acer monitor connected to the same USB-C to MDP adapter I used with the Mac Mini! Same Mojave version as well. How come? Is it a hardware issue with the Mini 2018?

So glad I ditched the Mini 2018. All problems I had with the Mini are gone with this one. No crackeling audio either.

I have been using HDMI + USB3/miniport and that worked with 2xLG24UD58 in 95% of all boots. I did that because 2xUSB3/miniport worked in less than 10% of all boots. I have now updated Mac Mojave release 6 (10.14.6) and I am happy to report that it looks like that fixed it (as was in the release notes). I can connect both monitors on USB3/miniport and booted twice with no problem. Of course the proof is in the pudding so the next few days will show if it works in all conditions but so far, I am a happy camper !

I was ever hopeful that 10.14.6 would fix the issue with two 2018 minis and two different monitors (CMV and BENQ) that worked perfectly with the 2012 minis, but no... the monitors do come back to life if left for only an hour or two, but if left for much longer, they do not awake. Monitors are connected via VGA to USB-C adapters (the 2012 minis had VGA to MiniDP adapters).

Checking the mini by logging in remotely shows that it thinks it has an internal monitor as it no longer recognises that it has an external monitor even if the monitor is turned off/on. Pulling the video cable and reinserting it does cause the mini to recognise the external monitor again - I'm just worried about the wear and tear on the USB-C connectors and so now set the monitor and mini to never sleep at the cost of power consumption.

I upgraded my Mac mini i7 to 10.14 6 a few days ago.

this afternoon, one of two monitors blinked black for about 10 seconds, and then re-appeared. This was after a long time of very heavy cup usage.

‘My mini already had one fan fail... apple replaced it.

‘’It seems the internals of the mini simply cannot reliably support two monitors . Whether it is a heat issue, or firmware, etc. I do not know. After 8 months of ownership and 20+ times that monitors failed, external hard drives do not mount, refusal to allow encryption of external hard drives, time machine failures, etc., I have had enough.

sorry, 10.14.6 has not cured the long saga of two monitors.

I bought a new i9900 dell computer today with a pretty nice video card.

$1700 including 1070 video, 16 mb memory, 512 gb ssd, 2 tb hard drive, lots of expansion options.

something similar iMac pro from Apple is $5000+ And still months away.

I have to get on, and the Apple Mac mini is simply not reliable as a high end workhorse.

sorry, the mini simply appears to be a poor design for heavy workloads with two monitors.

Apple has failed. Apple sold a product that does not work reliably.

I have now been on Mac Catalina os for a month now and my monitor that was loosing connection on a regular basis has not failed once in a month of use. I can now say for sure problem solved. As with friend who had dual monitor trouble, after update no more worries. Catalina beta was my answer. Hope this helps others.

Was anything specific mentioned in the Catalina update notes regarding this issue? I am having this problem with an LG Ultrawide 34" monitor connected by HDMI to Mac Mini (monitor inconsistently sensing signal from the Mac upon startup).

Sometimes double-pressing the power button on the Mac seems to get it to send signal to the monitor.

I've had “problem solved” under 10.4.6 for quite a while now, though what really seems to have solved it was using an ancient Apple adapter just once, presumably to really confuse the thing. The fix persisted past the security updates so I'm going to call it good.

I'm using a similar approach to brutus inquisitor to save wear and tear on the USB-C plug/socket for the video connector. The 2018 Mac mini now runs 24x7 unless I'm away for a few days in which case I shut it down.

I suspect it's a firmware issue (most likely the T2 iBridge firmware) that Apple seem incapable of fixing despite several firmware updates, not to mention the two Mojave 10.14.6 "supplemental" updates.