What should I do? In activity monitor kernel_task is using 249% of the CPU and the fan speed is 3601 rpm , what should I do? I have just recently formatted my computer.
iMac 27″ 5K, macOS 10.15
A multiple 100's percent kernel_task CPU usage generally means your Mac is overheating. When the intel chip gets too hot, the kernel_task will put the chip into a low power idle mode so it can cool down. Because the kernel_task is keeping control of the CPU for an extended period of time, the scheduler thinks the kernel_task is using a lot of CPU, when in fact it is trying to keep the intel chip from melting inside (literally).
You can have excessive heat from:
A multiple 100's percent kernel_task CPU usage generally means your Mac is overheating. When the intel chip gets too hot, the kernel_task will put the chip into a low power idle mode so it can cool down. Because the kernel_task is keeping control of the CPU for an extended period of time, the scheduler thinks the kernel_task is using a lot of CPU, when in fact it is trying to keep the intel chip from melting inside (literally).
You can have excessive heat from:
I have this iMac in the same room for 4 years now, I don't have air conditioning but have a fan for the computer during its operation, it is only recently that I have this problem. Probably my Mac have it's vents blocked since from start I did not have this cleaned inside.
I had this problem for months and tried all the reset advice and everything. None of it worked. It's actually being caused by dust build up in the fan vents. If you look at the vents under the monitor they will likely have a lot of dust. The kernel hogging of the CPU is meant to control heat, but Apple seems to have made it more sensitive during a recent update which makes it appear to be a software problem. I bought a plug-in blower online (because they are more powerful than canned air dusters) and blew out a huge amount of compacted dust from the iMac. Now my fans don't even need to turn on anymore and the kernel task has not once taken over my iMac. It was crashing between one and four times a day before from simple tasks like having safari open. I've been running five or six apps at a time now with no slowdown at all. I got my mac in 2018, so computers that are several years old are likely to be the ones having this problem. Spread the word: It's dust in the vents.
Since you have already erased your Mac's system drive, and re-installed macOS, the other option would be to try resetting your Mac's SMC.
Ref: How to reset the SMC on your Mac - Apple Support
I already have twice, and also tried ti zap the PRAM.
See my other reply in this thread about dust:
Can you tell me the brand and model of your vacuum?
Kernel _task runs wild in my iMac 2017 running on Catalina I have no other app open, I just have it re formatted due to this problem. Please help.
