iMac black screen - overheating
So… I tried everything from clean reinstalls, reseting NVRAM/SMC to blow the dust with a compressed air can. MacFansControl set to kick in after the temp reaches certain temp while using the screen at half the brightest …
The issue is that the computer will shut the screen off and after a few seconds (30 secs) the screen will turn on again. The cause is triggered on certain web pages with videos and other heavy on the GPU sites. I downloaded CINEBENCH to test this and after a few seconds of intensive GPU use I will get the black screen. I know the GPU/Mac is shutting it down to prevent damage.
I installed MacFansControl and all the values have temps ranging from 50ºc to 65ºc, with the exception of the GPU Diode that after reaching 103ºc or more will shut immediately. This is while running CINEBENCH. If the GPU isn’t in use the temp will remain at 60ºc.
What could be cause of this? The heatsink not working properly? Thermal Paste? Too much dust inside? Advice before sending it to repair (not apple). I think I could give it a try myself if the answer is to change the faulty part, clean it inside, or applying new thermal paste….
About the failing GPU case: What are the symptoms of a failing iMac GPU and how long does it usually take until total failure?.
My issue has been bothering me for 1 1/2 years approximately and I avoid it by only watching videos in places like YouTube, Facebook, DailyMotion, Apple Trailers, etc, not even 4K videos. Perhaps their videos/site have better optimization?
Working with Photoshop won’t trigger the black screen either. And I noted that after a clean installation of Mojave update the temps don’t rise in places they used to shut down the screen (like giphy com). But CINEBENCH will definitely push it to the limit and trigger it.
Any idea on how much money it will cost to fix (GPU) with Apple? As this is a 5 year old computer and I don’t have AppleCare anymore. I’m thinking about sending it to a technician that only works with Macs rather that paying Apple to fix it with a premium price tag. If I decide to open it, is there a way to really see if the GPU is the culprit? Like anything physical damage? Or some diagnostic software?
One funny thing is that I can’t get the black screen while in BootCamp, but I will try downloading CINEBENCH for Windows and testing the GPU again.
UPDATE: Booted from the BootCamp partition (Windows): downloaded Macs fan control and mason's CINEBENCH. Finished successfully and ran Open GL test 2 times, no black screen, Macs Fan Control showed the GPU diode reached 108ºC while the test was running. Could this be an OS/Software issue?
Or, perhaps the drivers for bootCamp are faulty and don't prevent damage by shutting itself down with high temps?.
UPDATE: After testing in Windows, I restarted into MacOS Mojave Safe Mode and tried to make it fail with no luck. The graphics are limited apparently.
After restarting normally into Mojave and running once again CINEBENCH I couldn't make it fail either even after running the test 3 time in a row. It did reach 108ºC each time.
For the last test, I tried running CINEBENCH, along a YouTube video in cinema mode and the landing page of gify com nothing! Temp reached 108ºC but keep going, The benchmark result just came a little lower because of the extra workload running.
Perhaps the days are getting colder but just a week ago I was getting black screens with CINEBENCH alone. Is this consistent with a failing GPU?
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