iMac 27" Screen goes black repeatedly, but then settles for a while?

I picked up my iMac today from Apple. They replaced the LED backlight boards. I've been using it non-stop tonight (about 6 hours straight) and have not experienced any problems. Everything on the Mac is how it was, the drive was not erased for a Lion reinstall. So far so good. If it starts acting up, I'll post another update.

Hey guys(and/or gals =P),

I just stumbled on this thread after digging up my 07 iMac that I've had packed up since it "died" on me 4 months ago. I am a gamer and was playing the new Diablo 3 game that just came out when I started having a similar problem. jjhaffner, glad to hear that you resolved your issues with yours.

I'm getting ready to do the flashlight test(I'm waiting for my display to turn off) and I had a question if anyone had a second monitor hooked up to his/her computer while the display was turning off? I wondered if a second monitor might remain on if it was a display issue, but to no avail, the external shuts off along with the main display.

I feel foolish right now also because I took it in to get diagnosed and repaired, and the tech said it was a logic board issue which would be a $1,200 fix, all of which would be chargeable to me due to my lack of continuing apple care. He then recommended that I just try and get some money out of it by selling it as an "as is" computer on ebay for spare parts. With that recomendation he offered to wipe the computer for an additional fee which, regretably (now that I have another idea to try), I accepted.

The shift+ctrl+eject hotkey doesn't work to bring my display back on, but I'm wondering if that's the case because I don't have any OS on it yet. I'm waiting for a friend to lend me his Install Disk to get it booted back up. Hopefully I can run the full setup fast enough before the screen dies on me. Or maybe I can just use a flashlight =). That'd be fun.

I'll update you what happens, but my big question is, did anybody try using an external monitor through this process and what did it do while the screen blacked out?

So I tried the flashlight test and I couldn't see anything, it was pitch black. Am I missing what I should be looking for or is it tough luck? What tips do you have to spot the picture w/out backlight?

I had this problem also. My hard drive stopped working because of all the sudden stops without properly parking the drive. I had to reformat it, but couldn't get the operating system to load. The fine Apple Geniuses were able to load a system. I took it home and it immediately started going to black again.

I did massive research on the web and solved the problem, and came up with a reason for the problem.

The cause is heat. The SMC fan is not cooling down the system which is then shutting down because of the heat.

There is a temperature sensor in the drive to supposedly prevent this. However, if you've changed your drive like I did, and replaced it with a drive that did not have a temperature sensor, thent he fan controll gets all confused, doesn't turn on properly, everything heats up and then shuts down.

This also happens on factory installed drives when the temperature sensor goes bust. A lot of Apple's early drives for iMacs and MacBooks were really cheap and the sensor failed. I had to replace my factory isntalled drive because it failed. (Thank you time machine).

The solution is a simple FREE software download called SMCfancontroller that turns your fan on at specific RPMs, and turns it off when you aren't overheating. I installed the software and haven't had a "go to black" moment since. The software can be downloaded here: http://www.macupdate.com/app/mac/23049/smcfancontrol

There is also another fan controller called Ultrafan which is also free.

There is a paid fan controller, but you don't need it. the free ones work exactly the same. The paid fan controller gives you a 1 HOUR DEMO, which is not enough to evaluate whether or not it works.

BTW if you drive has failed and you have a time machine backup, which backed up before upgrading to Mountain Lion, DO NOT UPGRADE TO MOUNTAIN LION until AFTER you've restored your time machine backup. Install Lion first, do your time machine restore and then install Mountain Lion.

I found out the hard way that Lion time machine backups are not recognized by Mountain Lion.

Hope all this helps.

Awesome suggestion! That fixed the problem for me. Now I just have to figure out how to get Lion back on my computer without repurchasing everything =). I just talked to apple about my journey, and they didn't give a rats ace about the problem, or at least in helping me get back to my previous OS (right now I'm stuck with Tiger). NOT IMPRESSED APPLE!!! Thanks guys for the help in getting a fix. It's weird because the fan app that I downloaded said that my computer's temp is -197F, so I think that's what my computer was doing, it was self preserving. Glad to have a fix.

I know it is a late response but, i have the similar problem. But the difference is I bought mine less than 4 months ago!? It's a late 2011 27 in. model. I brought it to the genius bar yesterday & they called me today that saying it passed all their test. My friend said that apple doesn't have any true "technician" at the store because they'll just hooked it up their system & run a diagnostic without them doing any hands on stuff?!? Meaning, they didn't open it up to see if their might be a loose connection or a short. In any event, they said they played all my HD videos via iPhoto (which I didn't care) & played HD YouTube vids. They said they let it play all night or whatever & no black screen. So I have another appointment with them tonight & I asked them if i can try to replicate it (hopefully)!!! They sure! So let's see what happens

27in Imac 3.1 Ghz intel core I5 screen goes black

I have the exact same problem, so frustrating. I took my Imac into the apple store and they said they couldn't reproduce the problem.

I found that if i turn my screen light down to the dimest setting it stays on without any issue. With full brightness it can happen every 30 seconds, though it is still unpredicatable. When it happens, the computer still runs playing songs etc. I have to tap my power botton to get the screen back up again.

I feel apple needs to take responsibity for this problem. Its not fair that people who pay over 2000 dollars for their product have to be jerked around. I have read countless post where they can't reproduce the problem then send you home with some bogus trouble shooting solutions. If this many people are having the same problem, it needs be addressed.

I hope we all can find a solution for this problem!!!

HERE IS THE SOLUTION

The problem is overheating. This usually starts if you have replaced the harddrive. My original harddrive was one of the really cheap Chinese ones that Apple had purchased with a high failure rate. They were crap. I replaced it with a great 2 terrabyte drive. Unfortunately after I replaced it I started having the going to black and shutting down problem. If you have the original harddrive it might be that it is working, but the temperature sensor is no longer working. I'd recommend you replace the harddrive, also. I bought my 2tb drive from ifixit.com. They are a great site. There are youtube videos that will walk you through replacing your harddrive, step-by-step, unless you have a local fixit place. Apple will not replace them with drives they don't sell.

The original harddrive had a temperature sensor that told the fan when to spin to cool everything down. Without that sensor the fan misreads the temperature and shuts the machine down. BTW this constant shutting down and revving back up is not good for your drive.

There are several solutions.

Solution #1: Try a free software program called smcFanControl. Here's the url:

http://www.eidac.de

Solution #2: If that doesn't do the trick you can buy a more robust fan controller for $29.95. Their site also has a complete explanation of what is happening:

http://www.hddfancontrol.com

Solution #3: Go to amazon and search for small desktop fans. Buy a really small one and just put it on your desk behind your MAC and run it to cool down the back of your Mac. That will also work.

It is a heat problem. I'm surprised that the people at Apple don't know this. I find that as long as my iMac is running at 52°C I'm fine. But once it gets to 54°C or more, it starts going to black and shutting down. Then when the fan spins down I can click on my mouse and it'll start back up and I'll be find for a while.

Like many of you, I took my iMac into the Apple store also and they couldn't replicate the problem because the store is airconditioned and the machines don't often get above 54°C. So they aren't going to shut down.

I hope this finally solves the problem for you guys. I know I was extremely frustrated. If it doesn't solve the problem don't hesitate to contact me at yvettegr@me.com.

Good luck. -- Yvette

ricardoh123,

If you still have the warranty... use it!!! I did. It saved me a lot of money!!! Roughly $1000.00!!!

OK. If you have an iPhone/iPad, record the issue, try to replicate it again and then show it to them! It's way better than explaining what the **** is going on. A recorded video is considered a documentation. (This is a continuation from my 1st post above) During my 2nd appointment, I've tried everything to replicate my issue and... No issues. They did another diagnostic, passed with flying colors, and I picked it up the next day.

I hooked up everything at home and then after an hour or 2, the same thing happened?!? My screen went blank with the music/email notification sound/volume going up or down still sounding off. I recorded everything on my iPad from turning it OFF to ON to doing the normal stuff I typically do. In this case, watching Youtube. I was unfortunate yet, fortunate to replicate while recording it on my iPad because it happened again and again.

Long story short I visted the genius bar a total of 9 times to resolve this issue!!! I complained about it & it went all the way to corporate customer relations.

Long story SHORTER, they replaced my video card, the mother board, & the monitor. My computer is working fine. No more blank screen with sound.

So the only issue (which happened 2 times so far but it's not a huge issue) is... I get these different color prints on my screen & then it freezes. The best way to describe these prints is like... removing a adhesive tape from a screen but the adhesive is still on the screen. I don't know but that is it.

So use your warranty & record all issues!!!!

wow, 9 times, thats insane. Sounds like they should have just given you a new computer : ) I use mine a lot for work. Its hard to leave it there for a week while they wait to replicate the problem.

Great idea to record the problem happening to have documentation. My computer is only covered for another 4 months so I really want to get this sorted out.

Does anyone know what their policy is for a defective product? Like at a certain point are you entitled to just get a fresh computer? Seems fair enough, thats a lot of your time to be wasted driving and waiting.

thanks for the reply

hmmmm

my computer will never go to a black screen if my light is at the dimmest setting, that's telling. Overheating maybe, but the computer's hard drive doesn't shut down, only the screen light. I can still use my computer with my mouse just no clue what Im doing

Also this happens even when using my computer in a really cold room.

It seems like the LED light over heats maybe?

so far Ive read a lot of fixes

logic board

power supply

stuff running on bus power

over heating

I wanted to put this out there so we can all find a solution.

thanks for your reply

i honestly thought i was going to get a new computer but i just wanted my computer back. Reason being, when i first turned it in, school was about to start less than a week. When I turned it in the 4th time, i asked them if they can expedite it since school already started. They said, "yes and it'll be ready tomorrow morning."

The next day I went to class and called them around 1pm and inquired about the status since I didn't get a phone call. they simply told me, "we'll call you when it is done." I told the rep that they said that my computer was supposed to be done in the morning today! The rep transferred me to a technician. The tech told me that they're doing a diagnostic. I asked how long will that take? He told me hours or even DAYS!!! I was cool with that and let it slide. But i was curious on "how long does it take to do a diagnostic."

Originally, all i wanted to know is, "where are they at with my computer?!?" Now I'm researching by making a phone call to apple support. I asked him and told him, "the apple store has my computer. How long does it take for them to do a diagnostic once it is connected to their computer system?" He said, "AN HOUR but definitley in a day!" I told him that the tech said it takes days!! the apple support guy told me he was lying!!! Now I'm super furious!!

AND that's when I've made my complaint based on the fact that he LIED to me.

Corporate customer relations made sure that my computer was getting top priority despite the fact that the tech at the store couldn't figure what's wrong with my iMac. But hey! I got new a video card, motherboard, and a new monitor!!!

In any event, video recording is best for documentation versus providing the symptoms based on hearsay. you can be super illiterate about computers but, if you show a video of what's wrong, they'll automatically know what's wrong with it... supposably

Yup! 9 times visits. 9 times means

1 time = drop it off for random going to sleep/black screen while using it but you can hear the music or video you're watching.

2 times = picking it up despite passing the diagnostic "with flying colors" that's what they told me. same issues happened again at home.

3 times = appointment; trying to replicate but couldn't. went back home... got the black screen again and VIDEO RECORDED it. They said that my outlet may not be giving enough power. I tested my outlets and there's enough power

4 times = drop it off and showed the video

5 times = pick up. New video card Black screen again and video record

6 times = drop it off and showed the video

7 times = pick up. New logic board Same issue and recorded it

8 times = drop it off and showed the video

9 times = pick up. new monitor and everything is working fine!!

despite having to go there 9 times, I saved a lot. I said, "$1000" from my previous post. Actually, $1375.00!!! And that's including labor. you have the warranty, use it!! why spend the cash to get the parts and trying to hook everything up yourself (if you have the tools, equipment, knowledge, and labor) or paying somone to hook it up?!?

But then again... I don't know how long you can live without your computer.

Hey!! since it is overheating, try vacuuming where the fan ***** up the cool air!! it is located on the back just above the power cable. the air intake looks round. It might be clogged with dust.