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iMac 2017 (late) thermal throttling issue

D

DN667

macrumors newbie
Original poster
Nov 24, 2009
28
1
Hello all,

A few days back we've suffered from several power failures at our home. Whilst the issue was resolved, it seems that this has broken my late 2017 27" retina iMac.

The system is slow beyond being usable, the fans are blowing at full speed continuously and after some digging around I've found that it is throttling the CPU speed due to supposed overheating. This really isn't the case: this issue starts happening right at the boot (even before Ventura is booting) and per the thermal readouts, the system hardly touches 30C (yes, I'm in a cold part of the world).

My question is.. how to fix this? I'm considering TurboMac to prevent the system from thermal throttling (which kinda feels like a last resort measure). Is there a better way? Might a sensor be damaged and would replacing that sensor resolve the issue?

Thanks, for somebody who's getting desparate ;)
 
DN667 said:
Hello all,

A few days back we've suffered from several power failures at our home. Whilst the issue was resolved, it seems that this has broken my late 2017 27" retina iMac.

The system is slow beyond being usable, the fans are blowing at full speed continuously and after some digging around I've found that it is throttling the CPU speed due to supposed overheating. This really isn't the case: this issue starts happening right at the boot (even before Ventura is booting) and per the thermal readouts, the system hardly touches 30C (yes, I'm in a cold part of the world).

My question is.. how to fix this? I'm considering TurboMac to prevent the system from thermal throttling (which kinda feels like a last resort measure). Is there a better way? Might a sensor be damaged and would replacing that sensor resolve the issue?

Thanks, for somebody who's getting desparate ;)
Click to expand...
First step to try is to "Reset SMC" which controls power and fans.

How to reset the SMC on an Imac? - Apple Community

discussions.apple.com discussions.apple.com
 
I was having almost the same issue. Installed Turbo boost switcher pro and an external boot drive and now temps and fans work correctly. Using Safari instead of Google/Brave browsers helped tremendously too.
2017 4.2 GHz Quad-Core Intel Core i7
 
Bigwaff said:
You wouldn’t happen to have Fusion Drive storage in your iMac?
Click to expand...
Nope. Actually.. I bought the 1TB flash drive back then, but it failed over a year ago. Ever since I've been running from an external SSD, which works just as fine. I don't suppose that the internal drive (which is still sittnig there, being dead) is giving me any troubles...?
 
OK, slight update. After installing and applying TurboMac as well as Mac Fan Control I've come to the point that I can make the system useable for a short amount of time. It's always a bit sluggish (not the snappy experience I'm used to), but somewhat useable. However, after some time the throttling is back. Powermetrics tells me this is due to PRO_CHOT and PRO_GHOT, which should mean that both my CPU and GPU are getting (too) warm. I'm disagreeing here, as the iMac feels pretty cold and the temperatures don't ever exceed 35C. Pretty confusing...
 
DN667 said:
Well that's an interesting tip. However, it seems that this program is not available for download? I get to their website, but their download location seems to be offline. I hope this to be a temporary issue...
Click to expand...
I purchased it from the author about 4 months ago. I checked today and its seems to be available here. If I remember correctly it doesn't work if you try to use PayPal?

 
Last edited by a moderator:
Chuckeee said:
Perhaps a more pedestrian, mechanical issue is to blame. Are either the air inlet or exhaust obstructed or clogged with dust?
Click to expand...

I'll check for that soon. I don't expect this to be the case as this issue 100% coincided with the power loss in my house. It would be great if you're right tho.
 
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