Chosen Solution
A friend tried to update their Mac to Sierra but the update failed part way through. Now the computer she tried the install on is running its fans constantly and the CPU usage is bouncing between 80%-200% almost entirely due to kernel_task. I’ve tried reseatting all the connectors on the board as well as an SMC reset and PRAM reset. I’ve also cleaned out the fans. Online people are suggesting messing around with system files, I’d prefer to avoid that solution if possible. Computer Specs: http://www.everymac.com/systems/apple/ma…
First a common problem in this series is worn HD SATA cable. You may want to first replace it. As you didn’t give us which model you have here I can’t tell you what guide to follow or what you’ll need for parts. Go to this site: EveryMac - Lookup and plug the systems S/N in it will spit out your systems specs. Once you have it paste the URL here so we also know. In any case you may need to wipe the drive down and re-install the OS.
