External monitor problem iMac 2017 High Sierra.

I am not quite sure I understand everyone’s solutions here.

1. You should always have an OS backup before you upgrade. (If you did not backup, now you know you need to backup, always.) Apple provides Time Machine, use it. My machine backs up every hour if there is an issue after any installation then I go right back to when my system was working.

2. If you are using your computer for work and it is working good... you should never upgrade, (or at least wait until all the issues are addressed with a .1 or .2 release). If it is not broke... If you need the new OS then run a dual boot so you can test your system. ( I have been running 10.13 off a flash drive.)

3. Purchasing a new monitor is not going to solve this issue. It is well documented now and I can tell you that the .1 beta 3 release has addressed my monitor issues so hopefully it will address yours. It has also introduced new bugs so I don’t see it released too soon.

4. Apple support is only as helpful as they are knowledgeable. New OS releases are very unstable and I would take any advise to buy new hardware with grain of salt. If you can’t revert back to a backup then just be patient, this OS is still fairly new. The kinks will be addressed.

Matthew

I agree people should always be cautious in upgrading, but please don't blame the victim here.

I've generally found OSX updates to be pretty good, only minor issues.

High Sierra has **MAJOR** issues.

My thunderbolt port *does not work*. That is not a "whoops" issue. It's not just monitors, it's the whole thunderbolt port.

Then there's the issue where the `WindowServer` process has a **massive** memory leak (and is seemingly so common that everyone I know has seen it) which means OSX actually has to be rebooted every other day (in my case).

Note I do have other issues, I'm just making a point here... These people aren't installing betas and expecting everything to work... they are installing final releases and things are very much broken and beta quality (early beta quality, even!)

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Sadly I did not receive beta3, but beta2 at least fixed the memory leak... beta 4 just released last night, hoping to find my thunderbolt port working again 🙂

I am not blaming I am just trying to explain the reality.

Do you think Apple would postpone an OS release even though it had issues?

I know new OS releases are enevidable, but High Sierra seems to be suffering from the lets get it out instead of lets do this right.

There are a lot of issues with High Sierra and you can see by an immediate supplemental release and then a .1 update that is in the works.

The best thing to do is be patient while Apple fixes things.

Matthew

It is absolutely a software issue they obviously disabled it . I have a mini DVI to HDMI connected to my laptop and I have the HDMI hooked into a switcher which illuminates blue when there's power going through it there is zero power going through it they obviously disabled that when we upgraded to macOS High Sierra among other problems you also cannot play PS4 remotely on your Mac now they're a bunch of other things that you cannot do as well as these apps are no longer supported Kinda ***** that you have to wait to you something that you've used probably every day I use my Mac to watch movies and now I can't . they need to fix it .

I spoke too fast... The system went asleep and back. It doesn't manage to stabilize (turning black, showing low resolution...). Seems the problem hasn't be fixed yet. It was stable when I totally shutdowned and restarted my computer. I don't want to do it every time...😟

FYI, my display is connected via a brand new HDMI to mini Display connector

Jesper/ All,

I to was having a similar issue running dual monitors after upgrading to high Sierra, my newer monitor would work however not my older dell monitor. I finally went and purchased a new monitor made by AOC pretty cheap, bought a HDMI to lightening port adaptor since my first monitor was using the HDMI port. Surprise after rebooting my Mac Book Pro all screens came up and no issue since. I hope this helps!

Wait before celebrating. Here's what I've observed.

First I fully restarted my iMac 27 (2013), then plugged an ASUS HDMI 27 via a HDMI to mini display connection.

for like an hour, High resolution, stable, no problem. Then, the ASUS starts to turn dark for one sec, then 2... and after 2 hours, got totally crazy (dark, low resolution) and fully unstable. I have also some random issues with my iMac display when on Google. So, based on what I've read and observed for myself, I have the feeling that the High Sierra OS has flaws regarding the video control, which will solved once Apple decides to tell us what is going on...

My personal experience with an ASUS 27 connected (HDMI to mini display) to an iMac 27: totally random and fluctuating issues. Can work well for 2 hours, then, begins to turn black for a while, or even doesn't switch on (even if detected in the preferences). From all posts, whatever the display and way to connect it, it appears that there's a flaw in video monitoring from the High Sierra OS, and it has to be fixed by Apple. It's quite upsetting to see that they don't communicate on it while, in the same time, they claim they provide the highest service to professional and graphism, photo, and media... "So Sad!" as a US President could say....😉

Resetting the VRAM doesn't work for me also, tried a couple of times.

I could get it to work when I update to the stable build or from the stable build to the current beta (which I'm in at the moment). But after a while it stops working again. This might mean that something during the macOs builds install process makes it work again, like some cache being cleared. Already tried going into safe mode and then back and no luck.

As I've said before, installing a new build solves the problem for me. I've installed the new beta that came out yesterday and that fixed it but I still don't know if it's a momentary fix or if the issue has been really fixed by Apple.

I'll check on the next few days if the issue comes up again.

Tried it and it worked after 1 shutdown. But its back, and I think the flickering is worst than before... Don't know what the **** is going on. Might try usb-c to thunderport display or maybe get a 60W adaptor if this is a power issue.

I had to buy a new KVM after updating to El Capitan to get 1920 x 1080 because VGA no longer worked. When I updated to Sierra, I had to buy two different KVMs, an Aten and a Lynksys. The Linksys was stable, but I just updated to High Sierra on my 2012 Mac Mini and cannot get the resolution. I just bought a connect pro and several HDMI EDID ghost adaptors and none of them solve the problem. I tried them in front of the KVM and behind the KVM in front of the Mac. I cannot afford to update my 2014 Mac Mini because I cannot do my job and personal work without it.

I love these Mac Minis but I just don't understand why I need to buy new hardware every year to use the same Apple devices. Much as I love these Mac Minis I probably need to make do with them through their life and then u ultimately replace with iMacs.

i have the usb c to hdmi/usb 3 output dongle made by apple and plug the hdmi end of the connector on to that -which works great for the monitor that has the hdmi connection, but my monitor at my other house only has the display port. i'd hate to think i'd have to use an adapter that doesn't allow for the power supply to be plugged in at the same time - plus i need the usb to connect the data cable as i use the usb ports on the monitor to run my back up drive, optical drive and external keyboard with its own usb's. i also have no problem using the hdmi to hdmi for my TV connection on the rare occasions i want to hook my laptop up to it. this is a macbook 12", not the pro that has two usb c connections

d3vinda you are a blessing!! Saw your comment and went to the link, downloaded latest display link driver and also updated my onscreen control software from LG. My Ultrawide monitor is now back and kicking!! Can’t thank you enough!

Having this very issue with the recent upgrade done today where I updated to High Sierra 10.13.2, I was running the older version of HS before this.. My external Dell monitor was connected via the MBP's DVI port to the Dell's HDMI. As soon as I did the update the external screen is no longer working with my MPB late 2011.

I did the drivers update. I know the trick of disconnecting the cord to the monitor and then reconnecting. If I keep connecting and reconnecting the DVI adapter eventually the system will recognize the external monitor is connected but no image will be displayed on that monitor.

My DVI to HDMI adapter is an apple adapter and I've had it for maybe 5-6yrs so I am going to try to see if a new adapter might do the trick, but as it has been pointed out before, it is rather suspect that this happened right after an update.