iMac screen goes black, but system runs fine in background

Heat Issue - I had this same issue with my 2007 imac after I upgraded to ElCap. The screen would go completely black while using the computer and it would only come back on after waiting awhile or pressing the computer power button multiple times. I tried everything suggested here, PRAM reboot, new keyboard, deleting preference log in profiles. Then I thought, what if the iMac is getting too hot and something is shutting down........I downloaded Mac Fan Control https://www.macupdate.com/app/mac/47386/macs-fan-control and set the available fans to turn on more frequently when upper temperature limits were reached. I had no idea my CPU and GPU were running at over 170 degrees. Well this SOLVED the entire issue of my screen going black. I have been running the imac now for 4 days, NO Black screen issues at all and the computer runs perfectly. Now, running the fans more frequently or at a higher RPM may limit there life a little, but a new fan is easy to replace. Hope this helps, one more free thing to try.

I tried a lot of stuff ;

- New keybord

- Screen settings

- Hitting my imac 🙂 and calling it rude words

Seems the best thing that helps is Macs fan control , once installed I still had it a few times but when I man. encreased the fan speeds the temp. stays low and my screens doesn't go black anymore ...

grtzzz Juan

I am not using OS X mavericks but just guess out for settings .

Please open system preferences and click on built - in display .

Check the options : Resolution default for display and adjust the brightness automatically .

---Please bare with me on this long post---

Hello all, I'm in a similar boat. Seems like I'm having several issues crop up right at once and after a certain point, it's costing me more money to repair the computer than to get a new one.

In early July this year my screen on my 2011 iMac started bugging out. Shutting down the computer and tried rebooting with no success. Took the computer in to a highly rated repair shop near me. They said the GPU died so I had them install another one. That cost $650.

Upon receiving my computer again, one of my two SSD drives failed and because the two drives were raided together my whole computer was unbootable. This was the same day I got my computer back from the shop, so of course I'm convinced they did something. I was able to unraid and reformat one of the drives by booting from an install USB. One drive appeared to be severely corrupted. I was finally able to recover the corrupted SSD drive, or at least I thought, but then the drive was intermittently being detected. I figured maybe there was a lose connection. I soldiered on with only one working SSD but otherwise working computer.

About two weeks after that, my computer fell asleep while I was gaming on my Xbox and listening to Spotify on my computer. I shake the mouse to wake up the computer and change the song but the screen remained black (song continued to play and I could even click in the right spot and pause the song). I was forced to hard reset the computer. Trying to boot up the computer the screen remained black. I searched online for possible solutions. I did PRAM and SMC reset a dozen times, tried changing my brightness, etc but nothing ever worked. Finally hooked the computer up to an external display and was able to operate it no problem.

I finally took my iMac back to the repair shop, I don't know if they did something or I'm just having all of these computer issues happening in the course of 4 weeks. I asked them to make sure they cables were all secure and nothing was loose.

I finally heard back and they said it's either 1.) The inverter board which would cost $150 to replace, 2.) the LCD which would cost several hundreds to replace, or 3.) they just absolutely would not know what it was.

Anyone have any thoughts of what it could possibly be?

I honestly don't know what to do at this point because I bought this computer only a year ago on eBay. I bought it used but its has a lot of great upgrades like 4 TB SSD raid and 2 TB HDD backup, the read/write speed is 4x that of a normal out-of-box Mac plus fully upgraded RAM, etc. It costs $1100 originally which wasn't so bad because I sold back my older iMac for $700 so I only got the computer for about $400. But after the GPU replacement of $650 and now whatever issue this is, I could have just bought a new computer.

Hi ,

I know the problem and it is a heath issue instead of a hardware issue.

Your screen goes black because your computer needs more cooling HD , CPU

You have to install Mac fan control so you can manualy encrease the speed of the 3 fans in your computer so the core temp drops. When you run spotify and some games it gets hot.

Cheers

I came across this issue on my late 2009 iMac 27 inch recently (Its been working fine up to Jan 2016 this year:

Symptoms:

-Screen panel goes black randomly while working.

-Screen goes off if the brightness is above 3/4 bars (for me it was progressive - 4 bars was ok, then it only stayed lit at 3 bars.

-Screen never goes off if the brightness is 100%

It certainly 'feels' like a hardware fault...

Ideas proposed so far:

Heat Related Hardware failure: Replacement of either Logic Board, Display Backlight (very expensive) Display Inverter ( not that expensive)

Risks: Permanent damage to your computer - further problems from taking everything apart.

My solution:

I was ready to sell my beloved iMac due to what I thought was an expensive hardware issue / wear & tear. Its NOT! Don't sell your iMac just yet!

Turns out there was a simple fix for me:

Install F.lux on your iMac. For some reason after I installed F.lux, I have no further problems with the display blanking.

I've been using what I thought was a dead iMac now for the last 72 hours with no problems at any brightness level.

To make extra sure, I disabled f.lux on my machine (Menu -> Disable) and it still works. I'm not sure whats really going on, but I believe F.lux is overriding the default behavior of the panel and preventing the blanking from happening.

Please try it out and report if you experience the same thing 🙂

After a serious scare, have a whole new iMac again!

Thanks,

Thanks for the suggestion Anonmusic unfortunately for me it didn't fix this most annoying problem.

I hope it carries on working for you

I've made a few comments here after getting this problem.

Re: 27' iMac (2011) Screen turns off

After discussing possible solutions with an Apple authorized service who ran diagnostics only to discover the problem was intermittent....maybe video card replacement, back light etc etc or even a new 27" Imac...

I just may have resolved the issue by nothing more than turning off "automatic adjust brightness" of all things in system preferences>displays just under the adjust brightness bar...

Interestingly this feature is only available on my 2011/12 27" Imac and not my 2009 20" even though both have El Capitan 10.11.6 installed.

Is this a definitive solution...it's only been a week but so far trouble free....only time will tell...

SOLUTION

You guys were right about needing to run the fans faster to cool it. When my late 2009 i7 iMac 27" is above 130F the screen kept shutting off. Lowering the brightness helped but didn't solve it. Now running fans at max speed, at 120F all is working great with max brightness. This took a LONG time to figure out but I hope it helps you. I'm going to look into getting some compressed air and maybe hire a pro to get some more thermal paste in there. Taking out the hard drive and swapping for a SSD should help to.

For the record, I am using fan software called TG Pro 2.18 on macOS 10.12.1 (Sierra) to control the fan.

It helped to have a remote software installed like LogMeIn or TeamViewer. I also setup a hot corner to toggle on/off sleep. When the screen goes black move the mouse to the corner, wait a few seconds and move the mouse again... it should turn on. To get it to stay on you need to boost the fan.

Too bad this isn't widely known, Apple needs better integrated fan software for older Macs. These problems will influence my decision making when I buy a replacement computer.

Hi Johnathan

Have you tried just turning off "automatic adjust brightness" in display preferences, I've had zero problems since.

Robert

Robert,

Unfortunately I don't have that option available in my display settings to try. I'm guessing the 2009 iMac model does not have a ambient light sensor?

The screen no longer goes black since using the fan software and configuring the fan speeds appropriately.

Well as long we've each found a solution that works.

I was all set to buy a new Imac, it was that close as we were given no definitive reason, even with a computer that was a given a clean bill of health, why the screen was shutting off and was extremely unnerving.

Still controlling fan speed or turning off automatic brightness are somewhat related in our case as it's directly related to software that control sensors that are relative to heat created by the display which is in turn is directly related to brightness....which in turn may be because of a bug or software glitch that prematurely and/or randomly tells the Imac screen to go into sleep mode but with no prevision (programmed command) to wake up.

Installing "TG Pro 2.18 " may just in in fact have had some similar effect in overriding this glitch, similar to turning off "automatic adjust brightness".

Just a thought.

Most definitely our solutions are related. When my brightness was full, the black screen issue occurred more often than if it was lowered. Currently I am aiming to keep my system between 40-50C (104-122F) with an avenge fan rpm at 1725 and it has not turned off once. My iMac runs as a server, it's on 24/7 so keeping it cool is a priority now.

I must say that I'm not overly impressed with Apple lately.

• I had to send in my iPhone to be repaired and my encrypted backup was corrupt when I tried to restore it. Apple level 2 support could not suggest any solutions other than future-proofing by paying for more iCloud storage instead of keeping a local backup (Google gives you 15GB cloud storage free, compared to Apple at 5GB)! Luckily I found third party software (iExplorer) to access my encrypted and corrupt backup so that I could retrieve my photos.
• My superdrive on my iMac was replaced by Apple techs under Apple Care warranty and still does not work.
• iTunes Match hasn't functioned properly ever. Songs are uploaded, not matched.

The list could go on...

I have been a loyal customer since the original iPod days and must say that there seems to be so many more software bugs and poor quality control lately. Keynote presentations are boring now without Steve Jobs, I often don't watch the entire event now. Techs aren't very knowledgable, they suggest basic solutions that you can find through Google faster.

I have been considering leaving the Apple ecosystem but with iPhones, iPads, iMac, Apple TV and App Store/iTunes purchases they have me locked in for now. I'll be replacing everything in 1-2 years time so we'll see what options are available then.

All the best Robert, glad your problem is fixed as well! If I do keep the iMac going, I'll likely replace the HD with a SSD to help with reducing heat. Apparently you can replace the superdrive with a SSD as well.

My life with Apple started back in the early eighties... programing them to run multi-image slide productions so I've seen my fair amount of bugs and whatnots along the way ....it's been an interesting journey but with no admittance to our currant problem it is as if no one is behind the wheel : (

I fought this problem for a whole year. Longer. Tried fans, everything. Nothing worked. Nothing. A great Korean tech guy nudged it into working for a while, then the right side of the screen went 50% dark. I wasted a year. My humble suggestion is to cut your losses and move on. Trying to get this problem fixed is a black hole.