How to Modify the iMac Fan Speedby Nicole Vulcan
Your iMac comes with a built-in fan that controls the internal temperature. It doesn't come with a native feature allowing you to turn the fan up or down, so if you want to control the speed or frequency at which the fan operates, you'll have to download a third-party application. The smcFanControl app will allow you to control the fan, though keep in mind that even those apps won't let you set the fan's speed below a level that is safe for the computer.
Navigate to the developer's website and click "Download" to begin downloading the smcFanControl application to your computer. As of June 2014, the application is optimized for Intel Macs with operating system versions 10.5 through 10.8, also known as Mac OS Mountain Lion, though it has also been tested and operates on version 10.9. Follow the onscreen instructions to download the application to your computer.
Restart your iMac by clicking the Apple menu and selecting "Restart." Wait for the computer to reboot. When the computer is restarted, you may see a temperature reading appear along the menu bar at the top of your screen.
Click the Apple menu, and then click "System Preferences." Under the "Other" heading, look for the "smcFanControl" icon and double-click it to open it.
Slide the bars under "Min Speed" to the left or right to adjust the speed at which the fans operate. Your iMac may have more than one fan -- thus will have more than one slider bar to adjust.
Adjust what information appears on the menu bar by clicking the dropdown menu next to "Menubar," and then selecting "Temperature & Fans," or another setting of your choice.
Click "Save" to save the changes you've made to the application settings.
- If you've replaced your iMac's hard disk or swapped it out for a solid state drive, you have another paid option for controlling your fan. HDD Fan Control is an application designed for iMacs that have had a drive replacement. It costs $35 as of June 2014, and will control your fan in much the same way as smcFanControl.