iMac screen goes black.  



I have a 2010 27” i7 iMac that has decided it no longer wants to display the display.

For the past few months the screen would randomly shut off every once in a while, almost as if it was put to sleep. Usually a few clicks on the mouse or a couple of taps on the power button would wake up the monitor. Then, about a week ago it became much worse. When starting up, the display will work for about 4 or 5 minutes before going black. Waking it from a long sleep will also see it work for a minute or two at most. Thinking it may be a heat issue I cranked the fans using iStat menus with no change. I’ve tried safe boot and resetting the PRAM, neither worked. Also watched the console when things go dark but didn’t notice anything that stood out. Luckily I still have our old Apple 20” lucite Cinema Display and an Apple DVI to ADC display adapter so this has become our “second” monitor.

I did open up the iMac in the past, once about 3.5 years ago to add a ssd drive when the spindle drive became too slow, and again a year later to replace said spindle drive with another ssd.

This computer doesn’t owe us anything, and it will be replaced after the keynote next week, but I was just wondering if there was anything else that I could try?


I had this problem for quite some time, but since I had a second monitor attached which always stayed on, I just lived with the problem (annoying but not catastrophic) for several months. I did notice that if I put my machine to sleep using hot corners, and wake it up manually, the primary iMac screen would come on momentarily but eventually go black again.  I tried all the other recommended corrective actions, with no success.  I finally got fed up with it one day, and disconnected the drive I used for Time Machine back-ups (in preparation to take it in for "repair", and the primary display came back to normal. I have not reconnected Time Machine and have not had the black screen of death since (going on 2+ months).

I have dealt with this issue for a while now. And I have tried EVERYTHING that I could find on any message board, blog, article, with the exception of opening up my imac. Nothing worked except 1) disabling the auto brightness, and 2) keeping my screen brightness down to the lowest setting (which made seeing anything next to impossible). If I did need to turn up the brightness, to see whenever my screen went black, I had to use shift+control+power, wait a couple seconds, then hit enter for the screen to turn back on, but it ALWAYS went back black until I turned it back down. I even thought it was an overheating issue and have been toying with the Mac Fan Control. Finally, TODAY (as in just a few minutes ago), I noticed that the clouds parted and it suddenly got brighter in my office. My screen immediate went black. I started wondering if the light sensor was doing it, even though I disabled the auto brightness. So I placed my hand over the top of the screen, used shift control+power, then hit enter and typed my password to turn the screen on. From there I turned up my screen brightness to the MAX, and my screen never went black at all. Took my hand off, and yep, back to black. So I went and got some black tape, and put it over the top of my monitor to block the camera, and whatever sensors are up there, and my screen is bright and staying on. It literally is a miracle. Like I said, my screen has been going black for a really long time, and nothing else has ever stopped it from happening.
Let me know if anyone else has success by covering the sensors.

👍Best of luck!

Firstly, requiring tape to cover the ambient light sensor so as to avoid the screen from sleeping is indicative of an issue that certainly requires diagnoses because it is simply not normal.

I suggest you start up the computer with command-R to get into the recovery mode. Remove the tape. Attempt to reproduce the issue while in recovery mode. If the issue is not reproducible then there is a software issue that is either system wide or user specific. If the issue is reproducible in recover mode I would bet my chances on a potential hardware issue.

1 Answer


I have 3 things you can try

  1. SMC reset
  2. From the terminal type caffeinate and hit enter. As per caffeinate's man description: caffeinate creates assertions to alter system sleep behavior. If no assertion flags are specified, caffeinate creates an assertion to prevent idle sleep. In affect, it prevents sleep component wide.

    Or caffeinate -d to create an assertion to prevent the display from sleeping.

  3. Considering you have already opened the mac up a few times, I wouldn't hesitate to suggest you open it up once more to ensure all the cables running the panel are firmly seated to their respective boards. It could be a thermal threshold that might potential loosen the cabling.

I am inclined to suspect a hardware issues here, this does not necessarily mean component failure but rather internal cabling coming loose due to thermal activity.

You mentioned that it has gotten worse, working only a few minutes before it goes dark and then waking it from a long sleep makes it work again for a short while. The long sleep might be enough cause related parts to contract and create a more firm grip as they cool. My first inclination is to analyze the cabling inside the computer related to the display but because it is the most intrusive you should check that last.

I don't necessarily suspect fault with the GPU because you reported the Mac working with another display.

The SMC reset should correct any misaligned readings as probed by the thermal sensors. I would absolutely do the SMC reset and then download the free Macs Fan Control and let it run at full to rule out thermal issues as the cause.

  1. Reset SMC
  2. Run Macs Fan Control and let it run at Max RPM (to analyze if thermals are causing the issue)
  3. Analyze if running fans at max has any positive impact to rule out thermal issues
  4. If while testing the mac operates as expected but with Max RPMs or somewhere in between you can have more confidence that this is a thermal related issue
  5. At this stage of your analysis it would be appropriate to isolate the issue further by investigating inside the machine, particularly in those areas that you intervened and perform a visual inspection. You should take this opportunity to blow any dust and so on using a can of compressed air. Then carefully disconnect and reconnect the cables coming from the display panel to their respective boards.

You said the machine doesn't owe you anything. The machine is still, even after all these years, an extraordinary performer. Since you have the skills and confidence to have cracked one of these open, consider fixing it before handing it down or selling it. If you don't have the time to do this please do your best to ensure it is correctly recycled, perhaps Apple can do that for you.

This post was modified 9 months ago 9 times by Alex Santos
This post was modified 8 months ago by Alex Santos