iMac screen goes black, but system runs fine in background

Try doing 2-3 SMC resets and see if that changes the behavior. Normally you do not need to use the power button to put the machine to sleep if you set up the timer to your liking in System Preferences - Energy Saver. If you have not done a SMC reset before please click Intel iMac SMC and PRAM resets for instructions.

If you only did 1 PRAM reset please do 2 more. You can also restart in safe mode, this will clear some caches. It is possible 1 or more us corrupt. Operate in safe mode to see if the problem still occurs. To restart in safe mode when your hear the start-up tone hold down the shift key until a progress bar appears.

Philip,

If you suspect a temp or fan issue I'd recommend two things. First is monitor the temp by installing iStat Pro and post the temps your machine is showing.

For the fan, if you suspect a fan or sensor has failed then run Apple Hardware Test in Extended Mode 2-3 times back to back. If any errors occur then it has confirmed you have a hardware issue and need to take your iMac in for repair. I don't have instructions for AHT but here is Apple's link:

http://support.apple.com/kb/ht1509

Did you run AHT 3X in Extended Mode back to back?

my one year old 27" iMac randomly goes black screen at least once a day..... I can hear itunes still playing music and machine running

nothing awakes screen besides hard power button a few times or turning off surge...

have any of you determined wheter a Graphics Card issue versus a software issue?

thanks,

Had this problem crop up in my 2008 iMac over last couple of months. Tried lowering the screen brightness, SMC reset etc.. in vain. It got so bad that it would only turn on every 3-4 days and would stay on for 10mins and then black again.

Took it to the Genius bar, new graphics card.. (parts + labor = $180), now 2 days later running strong.

Here's the line item from the repair. Add $39 for labor.

Hope that helps!

My iMac was doing the black out screen too. I read through ALL of the posts on this discussion.

Here was my solution:

> Disk Utility Repair. Twice.

> Turned screen brightness down, but not to 50% like other suggested. Just a bit lower than I've had it.

> I did notice that my computer was getting hot. By touch. I have iStat widget. My CPU temperature was reading 52˚C - 58˚C ... that's hot. My computer is well-ventilated and exhausts are clear from obstructions.

>SMC reset. Three Times. Let the iMac cool off for a good 4 hours.

After this. My iMac worked without a "black out" but only for about an hour. Then it happened repeatedly.

I did and Apple Hardware Test. 2 times in "Extended Mode". Recieved two seperate errors. One of those errors I looked up was about a "Fan faiing"

I downloaded and install SMC Fan Control. I set up 3 custom fan speed presets. Watched the temperature closely while I worked normally.

Video work with FCPX. Multiple windows open with Safari, Calendar App, Mail App, some finder windows. I also started to use Photoshop and Illustrator.

The temperature did start going up. I made sure that I balanced the SMC Fan Control to keep the temp under 50˚C.

3 days now. Hard working computer. Backups going, multiple drives connected. Applications and video and processor intensive work.

NOT ONE black out since I did the Apple Hardware Test and intalled SMC Fan Control.

Will post if a change happens. So far, I'm not seeing the need for an Apple Genius Bar visit. *fingers crossed*

Hey Everyone -

I've been reading these forums for a while, having the same issues as everyone else, off and on for the past year or so. (I posted here and got no real response, but to bring it into the Apple store - https://discussions.apple.com/thread/5818360)

I did all the tests again last night, ran a hardware test (no issues were found), PRAM, blew out the vents to get rid of dust, added the app for fan control. Turned the baby on again, and it still went black on me.

Found that the only way to get the screen back on again was the short cut shift+control+eject and then wiggle my mouse again to wake it up. But it turns off again after 30 seconds or so. So it's not really a heat issue. And I feel like it comes and goes. I went two months without it really doing this, and then it started up again.

I'm noticing the screen gets a little jumpy when I have the brightness at a low, which I thought would do the trick, and surprise, it doesn't. So now I have it really high, and my eyes are buring from their sockets!

I'm not on Apple care anymore, and don't really want to fork out the money to get it fixed, cause I want to invest in a MacBook Pro. But my iMac, other than the screen sucking, works like how an Apple "should be" working.

I was curious if purchasing a monitor in general (HP or Dell), and hooking it up to the iMac and sharing the screen would be a good second rate option (since it seems like it's the screen that has the issue and not the computer in general), and if anyone else has done this? I know it's kind of a second rate option, but I'd love to hear what people's advice on this would be.

On and on!!!

Tara

Instead of buying a second HP or Dell, you should try taking the iMac to the Genius bar and give them a shot. They usually give you a free estimate and the charges are pretty nominal Apple doesn't want to make money on repairs and its amazing how inexpensive their services are. In my case the graphics card fix cost $180 and now my computer is running strong for 4 months with no issues.

IMHO an external monitor hooked to iMac would cost you more and is a band aid solution than a real one.

Good luck.!

Have the same problem with black screen. I can ssh into the iMac. Is there any log that could give some clue to the problem?