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 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 4 months ago 10 times by Alex Santos
First, Reset the System Management Controller to Fix the Black Display on Boot
  1. Shut down the Mac and connect it to your MagSafe adapter and a wall outlet as usual.
  2. Hold down the Shift+Control+Option+Power button at the same time for a few seconds.
  3. Release all keys at the same time, then boot the Mac as usual.
  4. You can  connect with Apple customer support for more tips if above won't work.
This post was modified 4 months ago by Dave Hamilton