MacBook Pro fan won't turn off

MacBook Pro - the fan won turn off. constant humming


[Re-Titled by Moderator]

Posted on Sep 16, 2021 8:51 PM

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Question marked as Top-ranking reply

Posted on Sep 17, 2021 8:18 AM

mikemcf31 wrote:

MacBook Pro - the fan won turn off. constant humming


Old issue, new issue, what changed?



The fans on MBP are always on if the Mac is on— this is not an issue.


The fans idle ~1800-2000 rpm and you typically do not hear them,

they can ramp up to ~6000 rpm under a heavy load and sound like a jet engine—this is hard to ignore.


You can see from Terminal.app fan speeds and temps, copy and paste:

sudo powermetrics -n 1 --samplers smc | egrep -i "FAN|CPU die|GPU die"\n


Keep your Mac notebook within acceptable operating temperatures

https://support.apple.com/en-us/HT201640



Uninstall all third party apps that are Cleaners/Optimizers/Anti-Virus/VPN

these are all known to cause issues.




If your issue continues you can trouble shoot further you can:


—Try a SafeBoot https://support.apple.com/en-us/HT201262



Takes noticeable longer to get to the login screen, does a 5 minute disk repair before it fully boots up, and certain system caches get cleared and rebuilt, including dynamic loader cache, etc.

Login and test. Reboot as normal and test. Caches get rebuilt automatically.


In Safe mode third party system modifications and system accelerations are disabled, it removes malware, etc hampering smooth operation, however a reboot will put it back to normal mode.


2 replies
Question marked as Top-ranking reply

Sep 17, 2021 8:18 AM in response to mikemcf31

mikemcf31 wrote:

MacBook Pro - the fan won turn off. constant humming


Old issue, new issue, what changed?



The fans on MBP are always on if the Mac is on— this is not an issue.


The fans idle ~1800-2000 rpm and you typically do not hear them,

they can ramp up to ~6000 rpm under a heavy load and sound like a jet engine—this is hard to ignore.


You can see from Terminal.app fan speeds and temps, copy and paste:

sudo powermetrics -n 1 --samplers smc | egrep -i "FAN|CPU die|GPU die"\n


Keep your Mac notebook within acceptable operating temperatures

https://support.apple.com/en-us/HT201640



Uninstall all third party apps that are Cleaners/Optimizers/Anti-Virus/VPN

these are all known to cause issues.




If your issue continues you can trouble shoot further you can:


—Try a SafeBoot https://support.apple.com/en-us/HT201262



Takes noticeable longer to get to the login screen, does a 5 minute disk repair before it fully boots up, and certain system caches get cleared and rebuilt, including dynamic loader cache, etc.

Login and test. Reboot as normal and test. Caches get rebuilt automatically.


In Safe mode third party system modifications and system accelerations are disabled, it removes malware, etc hampering smooth operation, however a reboot will put it back to normal mode.


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MacBook Pro fan won't turn off

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