Sidebar Sidebar
Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.

2019 27" iMac Fans at Full Throttle ... Any Suggestions?

jmoore5196

jmoore5196

macrumors 6502a
Original poster
May 19, 2009
845
348
Russellville AR
I've attentively read all the threads I could find on this topic and I've purchased Macs Fan Control, HDD Fan Control, iStat Menus, reset the SMC ... all to no avail. I have to produce audio on a daily basis, which is impossible with iMac fans running at 3600+ rpm. I'm on the verge of selling the iMac and going to a MacBook-based workflow.

My iMac is a 3.6 i9 with 32GB RAM and a 1TB SSD. I've had it since the fall of 2019.

On occasion, I can shut down the iMac at night and pull the power plug, then leave it out of the socket until the next morning, at which time the fan behavior is normal for several hours.

If I do leave the machine plugged in after I log out at the end of the day, the fans often spin up in the middle of the night, seemingly of their own accord.

Sometimes, just using the machine for an hour or so will - for no apparent reason - induce the fans to throttle down. I don't really have any high-usage apps ... I use Adobe Creative Cloud apps daily, but that's about it. I do no video editing or gaming at all.

If anyone has any suggestions, could you share them? I'm at wits' end.
 
It sounds like the system management control (SMC) is out of whack. Pulling the plug from the AC socket and leaving it for several hours or off overnight resets the SMC. But then it goes out again. I recommend contacting Apple since your iMac is still under Apple Care. You may wind up having to send your iMac in for repair since the Apple Stores are closed. Don't know what the repair will involve but it may mean changing out the logic board.
 
  • Like
Reactions: throAU
+1 agree. In the mean time you could try Turbo Boost Switcher if you haven’t already. I have a 2017 i7 functioning normally but the turbo boost off makes a real audio difference to me keeping the fans much lower at full CPU crank (which is still like 4GHz not 4.4 I think so not huge loss)
 
I'll certainly try Turbo Boost Switcher! Thanks.

At the present, unplugging in the evenings and plugging back in the next morning seems to solve the problem. I've no doubt I need a new logic board when the Apple Stores reopen.

I really appreciate the responses.
 
Another thing..... You should probably contact Apple support and get on the record with your problem. No telling how long Apple stores are going to be closed. I believe Apple will provide you with shipping materials and prepaid to them if they decide you need to send it on in. But either way, get on the record with them and document everything.
 
Just to bring everyone up to speed on this little saga, I did take the iMac into the Apple store is early July. I was told that all the hardware was functioning normally.

The tech’s only suggestion was to do a manual reinstall of a recent back up. He wasn’t specific about what element of migration assistant might have been responsible for the SMC issues.

I did tell him I wanted the issue noted in case I could not resolve it within my warranty period. If reinstalling the OS and then manually copying over my files doesn’t produce any benefit, I think I’ll just sell the iMac and move to a MacBook Pro.
 
Take a video of it happening. That will often force their hand. The issue sounds intermittent so they aren’t going to be able to diagnose it with their standard tools. Fans often “fail” to max RPM when the sensors aren’t reporting back any data.
 
rkuo said:
Take a video of it happening. That will often force their hand. The issue sounds intermittent so they aren’t going to be able to diagnose it with their standard tools. Fans often “fail” to max RPM when the sensors aren’t reporting back any data.
Click to expand...
I'm well aware of how the fans in my 16" MBP can really ramp up when connected to my LG display. But they're bearable in contrast to the roof-lifting blast from my iMac.

I'll certainly video the next occurrence. I'm not sure another trip to the Apple Store is in the cards for me, though ... I'm so tired of dealing with the problem that I just want to move on to another piece of hardware.
 
I wanted to update this thread: I wiped the hard disc and reinstalled piece by piece via drag-and-drop. I tested the system after adding each component; the overall effort has taken 3 weeks, but it's been worthwhile.

The typical fan speed now seems to be around 1450 rpm, which is bearable.

However, the fans ramp back up anytime I launch an Office365 app or OneDrive. For example, I just launched Word and the fans spun up to around 2600 rpm almost immediately. When I quit Word, the fan speed dropped almost immediately.

I'm not charitably inclined toward Microsoft, but I admit I find this rather strange. Any ideas why MS apps might tax the system in this way?
 
You can install a temperature monitoring app. The fans should correlate directly to the CPU temperature and likely CPU activity (or GPU activity). There's really no mystery beyond that ... examine the process of the offending app in more detail and maybe you'll find something.
 
I installed temperature monitoring apps some time ago. As I said, I'm not inclined to like anything Microsoft produces, but I'm unsure why the modest demands of a word processor would send my fans to full blast.
 
Well, the all-on, all the time problem reappeared, so I called Apple. This time, their remote diagnostic could see a problem with the fans. I got a service appointment with an authorized service center and dropped off the iMac on Sunday. We'll see what happens next.

I cannot calculate how much time I've squandered on this issue. Meanwhile, my 16" MBP is doing desktop duty, with fan speed averaging 1800rpm. No complaints there!
 
You must log in or register to reply here.
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.
Top Bottom
Back