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Model A1419 / Late 2012 / 2.9 & 3.2 GHz Core i5 or 3.4 GHz Core i7 Processor, ID iMac13,2

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Flickering Backlight, but not in Safe Mode

Hi, my main iMac screen is flickering spastically and annoyingly. But all is well in Safe Mode, and the two Dell monitors I have attached to the display ports all work great. What can I do? I was thinking if I knew the NVIDIA Kexts that run in Normal mode, I could somehow try and exclude them. I’d just run in Safe Mode, but I have no Audio device there. Any advice? thx!!!

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When you are running in Safe Mode you are not using the dedicated GPU instead you are using the intergraded graphics engine inside the CPU. Give your symptoms I suspect your GPU is failing or overheating.

Lets give this a try install this app TG Pro This will allow you to more effective monitor your thermal load. You will want the full version so you can gain access to the logging function. Post a snapshot of the main window manning sure all of the sensors and fan is visible for us to see how it looks when you encounter the issue Adding images to an existing question

If you could this new You may need to open the system up and give it a good dusting. This is not a trivial task in the newer models as you’ll ned to get this kit [linked product missing or disabled: IF174-005] as well as the cards (2 sets) Plastic Cards and lastly this [linked product missing or disabled: IF145-224-2].

Besides the tools and sundries from iFixit you’ll want to get a small soft paint brush to help loosen the dust and a can of can’ed air to blow it way.

Plastic Cards Image

Product

Plastic Cards

$2.99

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2 Comments:

Great answer. But is there anyway to just programatically (remove kext file) so that when the machine boots in Normal mode, it just uses the CPU graphics? I'm looking for a quick fix until I can get a new one. I put the iMac behind two 24" displays, and that's working for now, but not ideal. Thx!

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Well thats going to cost you! ;-}

Yes! its called gfxCardStatus

But before you go down this path lets get a capture of your systems thermals first.

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