iMac screen goes black, but system runs fine in background

You did reply gomoweb. Thanks.

I'm just a little reluctant to bite the bullet right now. I can't face the thought of reinstalling all the apps and getting them back to where I like them.

I guess it'll happen one day when I'm at my weakest and the tears are flowing down my cheeks.

It's just frustrating that even though myself and I'm sure many others have submitted reports to Apple and we're not seeing any response. Feeling abandoned. 😟

Still confused gomoweb, but if it's software related as you say, then it has to be something related to the system management of the mother board or similar, not related to the macOS version installed, because after some more tests that I've done today I can confirm that affects also when the macOS system is not launched yet.

My problem was going worst everyday... yesterday and this morning, my iMac screen remains on just for few seconds after start the computer, and practically instantly goes black. When I try to select with which partition I want to start the computer pressing the ALT key of the keyboard after the chime sound, also the screen goes black after few seconds and I can't see the drives to select. Also, after read your message, I've tried to create a Bootcamp partition and install Windows 7 on it. The problem still persist, even while I was installing Windows, the progress bar and the message "Windows is installing" was showed, but the screen of the iMac went black and I had to continue installing through the second display that I have.

So, perhaps here there are a lot of people talking about a similar problem, but while for some of them perhaps it's software related, I think for others can be perfectly hardware related. In my case, it's obvious is not only related to software, or at least not related to my macOS version, because the screen goes black also when installing Windows on Bootcamp, when starting the system from a recovery partition, or even in the disk startup selection option, etc.

But well... you're right in one thing: certainly there's something that affects the stability of the issue, and when we play with the system doing changes, somedays the issue seems to disappear or appear less time. An example:

Some hours ago, just after try to install Windows on bootcamp and see that my problem still persists even when installing Windows, I have done 3 SMC resets, 2 PRAM resets, tried again to start from a recovery partition (it asked me to pair again the magic mouse and apple keyboard with bluetooth) and finally deleted again the Bootcamp partition. Well, it's strange but since then, now I'm using macOS normally and the iMac screen remains on for more than one hour... Sure it will become black again later, but now it's more stable than before doing all of this things, because this morning the screen was going off constantly, just after 5 seconds.

So... yes, really there's something that affects the leds management, I don't know what is, but something seems to have some incidence on it. In PCs, I remember that exists something called the "BIOS" that manage the hardware when the system (Windows) is not installed or launched yet. Perhaps there's something similar in Apple computers (not only EMC or PRAM) that becomes corrupted and causes this problem... And perhaps a new fresh installation like you did, can help and change something.

Thank you for sharing your experience. I took my iMac (mid 2010) into the Apple authorized independent repair shop, and he said he would need to keep it for a few days and run some of the same diagnostics that Apple did. He says Apple just want us to buy new computers.

I couldn't leave it and lose that many work days. Still working fine with external monitor, but at 1920 width. I definitely am not going to invest in a new display screen.

Maybe a clean install.

Hi ChoPraTs Yes you could have the screen going black during installation of windows because it is being installed through the OS as boot camp is part of OS. I think the difference between our two systems is I had windows installed before I started having the black screen problems. Unfortunately, you're trying to install it on a corrupt system. I take it you use timemachine and have a backup of your current system if so download the latest version of the os there is a good article on livewire about the steps to take see the link below. I would bet a pound to a penny that your problem is software related. and there is nothing wrong with your hardware My Mac has now been running nearly 8 or9 weeks the last 7 days now with continuously and the screen has not blacked out once. There is something similar to the Bios on a Mac as Macs run on the Unix system. Once the Apple logo appears on the screen that is when the OS takes over. Good luck I hope you fix your problem I hope some of what I have said helps How to Perform a Clean Install of macOS Sierra

Gomoweb,

I think I'm going to do a clean install on my iMac to see if it helps. I upgraded to Sierra about 5 months ago. I believe that's when the dark screen started happening. You don't suggest going back to a prior system like Yosemite or Mavericks?

Hi, Michael I didn't I'm Running Sierra 10.12.5 if you click o the link I gave ChoPrats tit will give you one of the best set of instructions on the how to do a clean install. also be for you start I would suggest printing out the instructions and reading them through a couple of times to get your head around them. I'll let you into a little secret "Most people don't read instruction manuals and that's why I make a good living out of fixing Computers" Also you'll need a 16GB usb stick. Good luck and let me know how it goes.

Back on June 26 Apple store wanted to try a software solution, ie., reinstalling Sierra. It didn't work. They said next step is to replace display. I didn't think it was worth it. I ordered a new iMac—the 3.5 GHz. They refunded all the payments I made for repair. New computer is nice and fast.

OK, so there seem to be several causes of this similar problem from reading the replies here. Here is another cause!

My iMac 27 Mid-2011 has had this problem for a couple of months and I have been SO frustrated with it. I use my iMac for Photoshop and Lightroom in my studio and alongside it I have a Windows 10 machine for bookings, email, general browsing, etc. I just find it easier with dedicated machines. The iMac screen would go back at regular intervals and sometimes would only stay awake for a few seconds before going black again. I figured out that if I gave it the Cmd, Alt, Eject to actually put it to sleep, then I could wake it up, but trying to wake it up without first putting it to sleep, just didn't work.

I also noticed that my Windows machine was intermittently having issues with response to the keyboard and mouse. They were around 20" away from the machine and moving them closer seemed to work mostly, but sometimes it didn't. More frustrations! I then started wondering if with both machines running Bluetooth keyboards and mice it was interference. Switching off the Windows machine didn't solve the issue, but then the penny dropped. Mobile phones! I have two mobiles in my pocket. An iPhone 6S for personal use and a Samsung Galaxy Edge 6+ for business use. Both had Bluetooth switched on. I disabled Bluetooth on both mobiles and Hey Presto! Problems with both machines solved.

Interesting to read your story gohunter, I will save that for later in case my blackouts come back but here's my very different story which also seems to have fixed my iMac. I have been suffering with screen blackouts for years now—I think there’s some confusion between the 2009 backlight failure and the mid 2011 blackout problem. For the record, mine is the 27” mid 2011 with HD 6770M video card and Mavericks. I have had long periods (months) without blacking out, usually with the brightness set to 3 blocks but recently it became unstable again and I was constantly having to use Ctl-Shift-Eject to see what I was doing. (My iPhone is always on the desk with Bluetooth on)

So my latest fix came about when I was to trying to get the Fan running faster with SSD-Fan-Control - thinking this was an overheating issue. This was giving me some success and I was running with the screen much brighter for longer periods but it didn’t last. Interestingly the iMac was running pretty warm at the back even with the fans blowing hard and getting quite noisy. I then accidentally launched SMC Fan Control - I forgot it was even installed and it’s not likely to be a good idea to have both these fan control apps working on the same machine. So I set SSD Fan Control back to Auto and hit the Reset button in SMC Fan Control to return to defaults. That required a reboot and I did PRAM reset for good measure at the same time and now my iMac is perfect. Running much cooler, no fan noise, and no blackouts with the brightness midway. One other thing I did was to tick auto brightness in the Display Settings. So out of all this, I don’t know what actually made the difference but I am very happy with how things turned out. Hope it helps someone.

I was having this same problem as well and so the computer has been standing unused for a couple of months until i could afford to fix it - in the meantime i have got a new iPhone so I went to switch on the iMac so that I could quickly back up my old phone before the screen gave out, then I could plug in my new phone the next time and the back ups would just run in the background even after the screen went off was the theory. However when I went to switch it on it was making the startup noise but nothing was happening on the screen at all and then the computer was just switching itself off and not even trying to boot up..??!!! HELP!!!!

Experienced this "black" screen problem on my late 2009 iMac. It started a couple of months before it was booked in to have an SSD drive fitted. It happen twice a day initially, but by the time it was taken away to have the new hard drive fitted it was every ten minutes or so. During the SSD install it also had its logic board replaced due to faulty connector and upon return the machine is so much faster, but the black screen problem is still there. Done the PRAM resets and the other one and turned down the screen brightness ( which helps prolong the cut out time but still not a permanent solution). Tried fan speed software, but no better.

Decided this morning to look at energy saver settings and discovered they were set at 5 mins for display and computer sleep. I increased them to 1 hour, ignoring the warning about being more costly to run and also wearing out the display and drive sooner as I wanted the thing to work!!! and voila the black screen has vanished. I've even turned the brightness back up to full which previously seems to crash the screen to black and no problem.

So don't spend money on software, or hardware try this simple adjustment of your "sleep" settings in System Preferences - Energy Saver first and see if it that resolves it for you. I assume an IOS software update must have altered these settings at some point as Ive never been into Energy Saver before

Thank you to everyone who shared their story. I have been reading through the posts here and on the web, watching videos on YT the last few nights trying to ascertain the correct fix for the blackout screen problem on my, late 2009 Imac 27” 2.66 GHz i5 16GB Ram ATI Radeon HD 4850 512MB. I sincerely appreciate all of your notes and experimentation. This is my fourth Apple computer in 21 years, the last was a short-lived G5, and I hope they will eventually come clean and address the issue.

My previous diagnosis may have been correct, it certainly worked much better for a few weeks but then for the first time I started having the well known issue where the left side of the screen goes dark. I followed the fix on YouTube: (Apple iMac 27" Dark Side Screen Failure - The Manufacturing Fault Apple Will NOT Admit!! - YouTube ) -this involves digging out the plug at the back of the LCD screen and soldering the wires directly to the board. Not easy to do, I can tell you. But now several weeks later I'm very happy, and the iMac has been good as new.

This is very frustrating and so many people seem to have the problem. I'm a 2010 27" iMac user. I am a little surprised that Apple didn't issue a product recall. It also makes me nervous about ordering parts on eBay because how far along are they from failure, too?

At the moment, I have El Capitan installed, having firstly gone back to Snow Leopard just to see if the problem exists there, too, which for me it does. I have tried so many of the suggested quick fix solutions but none have worked, sadly, though I greatly appreciate all of the suggestions given.

Clearing the PRAM briefly seemed to work but only for a minute or so. The only way I can get the iMac screen not to go completely black is to have the brightness set to its lowest point. If it's a very cold day, I can have it around 20% higher than that but not for long.

This model has had so many problems, for me, including the noisy Seagate hard drive. I am going to strip down the iMac and replace the thermal paste on the CPU and graphics card, which I should have done long ago, the temperatures were a little higher than other users and, in my opinion, when under load for long periods, are really too high for long term stability of the iMac. I resorted to using the iMac as a screen for a computer but it still got very hot. Like a lot of people with the 2010 27" model I have cloudy areas on the screen from dust that requires very carful surgery (ribbon cables) and aluminium tape (does anyone know what tape Apple/LG use) to remove that dust.

I hope the next generation of domestic iMacs feature the same cooling system that the iMac Pros use and that there is some concession made to people who want to upgrade memory and storage. It's unlikely that my replacing thermal paste and re-seating cables will make a difference (to the blackouts) but I will report back, either way. The iMac is long enough out of warranty that it seems worth a go.

My mid 2011 iMac hasn't so much as blinked since I did the fix in my previous comment. research this fault and the fix for that will cure your black screen too: (Apple iMac 27" Dark Side Screen Failure - The Manufacturing Fault Apple Will NOT Admit!! - YouTube )