By default, Apple runs your Mac’s fans automatically—with no way to configure them—and it ramps them up when your system gets too hot. The free Macs Fan Control app lets you manually control your fans. There are two reasons you’d want to do this—to allow your Mac to run faster but louder, or slower but quieter. Apple’s auto control aims for somewhere in the middle.
A Few Warnings
Your Mac throttles your CPU when it gets too hot, slowing it down significantly until the temperature gets under control. Usually, this kicks in before the temperature gets too high, but you can manually push your CPU farther by turning the fan speed up farther than Apple usually allows. This makes a lot of noise, which is why the auto-control tries to slow it down.
On the other hand, if you hate fan noise, you can manually turn them down. Keep in mind that this will make your system run a lot hotter, and could lead to system instability if you let it go too far.
With either option, you should monitor the temperatures of your CPU and other components and make sure you’re not causing damage to your system. It’s also possible that running fans at max speed for extended periods could lead to damage, so try not to torture your laptop.
Controlling Fans
Get started by downloading the Macs Fan Control app and moving it to the Applications folder. When it starts, you’ll see a list of all your fans and the option to set custom controls. “Auto” keeps the default behavior, but opening up “Custom” allows you to set a specific RPM value, or set a target temperature.
The sensor-based value option mimics the automatic behavior but lets you select how hot you want your system to be. You can push the maximum temperature higher if you want more performance, or lower if you’d like your fans to be quieter.
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Source: How-To Geek
