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Model A1312 / Mid 2011 / 2.7 & 3.1 GHz Core i5 or 3.4 GHz Core i7 Processor, ID iMac12,2

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iMac keeps rebooting at startup

On startup my mac has a gray screen, the apple and progress bar come up and then stops halfway through. Then it waits a few minutes and tries to reboot. I get the same thing.

I put a new HD in, thinking that was the problem and installed new MacOS.

Was working fine for 6 hours and then the screen went gray again and it keeps rebooting.

Hardware test says its all okay.

  • Tried safe mode.
  • I can get it to come up in Target Disk Mode.

Also Tried:

  • Zapping NVRAM
  • Reset SMC

Any other suggestions?

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Does anyone think this is a graphics or logic board. Hardware test showed everything was okay.


Steve, I have same problem, did you get a solution? I would be grateful to hear what it is.

Robert H


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Hello I also have the same issue happening on a 27” imac. Luckily I do have access to the tool in our IT department and have an IT background. i was able to use Disk Warrior recovery tool on the USB stick. The imac booted from the USB stick and I was able to perform the hard drive repair. DW did detect a problem with the partition but only when it did a deep scan otherwise it said it was fine.

It was fine for some time then it started happening again.

I did have the hard drive replaced about 3 years ago from an apple certified repair company.

I have a time machine backup. I’m not worried about the data. I’ll have them swap the hard drive. It’s the cheapest solution at this point. I don’t have the money to replace the logic board. I’ll post the result when I get it repaired.

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Hello, Just an update.

I swapped the HD with an SSD and the white screen issues arose.

It was the GPU on the motherboard. I brought it to a certified mac tech and they "baked" the logic board. I still have my SSD drive in the mac and I'm running the OSX SSD fan software.

The cost was a little over $200 dollars Canadian for the repair and he gave e a warranty of 3 months.


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Try to reinstall OS X again. Shut down the computer, then press the power button. Immediately hold the Command and R keys. Continue holding them until you see an Apple logo or a spinning globe. Click on "Reinstall macOS". An installer should display itself. Follow the steps it guides you through. Keep in mind that this will erase all of your data on the drive you are installing macOS on.

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This did not help I used Command R - nothing but gray screen.

Tried command option R and comes to a spinning globe, progress bar goes to the end and I get another blank screen.


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I had a similar problem not sure if it’s exactly the same as yours without seeing your machine… The first time it happened I did an internet download of a new operating system… Then it died again a little while later maybe two weeks or less I hardly use it so I’m not sure but it wasn’t very long…At this point I’m pretty sure it’s a faulty hard drive. The other thing I noticed was the hard drive no longer showed up in disc utility… I like to play around with old iMacs as a hobby so I have an external SSD with an apple os on it… I plugged it in via external usb 2.0 on the back and it boots every time... I’ve picked up a couple of Samsung SSDs and I’ll replace the 1tb disc drive with those. I’ll see if I can add a picture to this.

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Steve McGowan zal eeuwig dankbaar zijn.

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