iStat Menus help control the speed of fans in your Mac. Please note that fans are always controlled by the System Management Controller (SMC) in your Mac — iStat Menus simply asks the system to increase the lowest fan speed. It can’t lower fans below the speed the SMC would normally use.
Fan control in iStat Menus works, even when the Sensor item is off.
There’s two ways to change the fan speeds of your Mac.
Setting fan speed via the menu
The easiest way to set fan speeds is via iStat Menus’ sensor dropdown menu. To set the fan speed, simply open the Active Set submenu, and slide the various fan speeds as desired.
Setting fan speed defaults
It’s also possible to create sets of fan speeds, and assign them to different situations — you can elect to use different fan rules when on battery power or when you’re charging. To edit the fan rules, click Edit Fan Rules from the sensors tab in iStat Menus.
You can then change the set at any time from the sensor dropdown.
Off vs default
With the fan control set to Off from the Sensor menu, iStat Menus will not control fans at all. With the fan control set to Default, the default fan speeds set within iStat Menus will be used.
Fan control issues
If you’re experiencing issues with fans, it may be worth Resetting your SMC.