Mac Running Hot? Control the Fans

With summer weather* and high-powered Macs comes the inevitable: heat. Your Mac should be able to manage that heat with its own fans, but sometimes a little tweaking can help considerably.

There are lots of variables when it comes to managing heat in modern, high-powered Macs with Intel Core i5 and i7 processors. The Energy Saver settings, the workload on the Mac, say, with heavy video processing, and the ambient conditions are a few. Some household rooms are not well ventilated, and sometimes the Mac is put to work in a place that has some summer sun and not a lot of cooling.

Our Macs have temperature sensors and fans, and Mac OS X is designed to kick those fans on when needed. But those fans are also designed to run quietly, and that means low RPMs, perhaps in 1,000 RPM range. You may net even be able to hear your Mac’s fan running that that speed. However, there may be times when you just need a little extra fan speed — something you can hear and offers warm (no pun) fuzzies.

smcFanControl is an app that’s designed to give you that little bit of extra manual control for judicious use. It’s an app, but its user interface is restricted to the Mac OS X Menubar for ease of access and a good user experience. Here’s how it looks on an older MacBook Pro:

SMC Fan MacBook

Note that it sees the two fans, left and right. You can check the sync box to slave the sliders. You can control the display of the temperature and fan RPMs in the popup, and even change the color of the text in the Menubar. By bumping up the minimum RPM a few hundred RPM, you may get just what you need. Other settings allow you to create a named setting based on the power source. That’s what the “+” does in the upper right corner. In this app, nothing is altered until you click the “save” button at the bottom. For safety, all settings return to the default when the Mac is restarted.

It really is a nifty app because you can monitor the temperature of your Mac’s insides with just a glance at the Menubar.

Here’s how it looks on an iMac.

smcfan iMac

Note that, in the case, it sees three fans: the optical disc drive (ODD), the hard disk drive (HDD) and the CPU. It doesn’t make sense, here, to slave the sliders because you probably don’t want to or need to change the ODD default setting — considering how seldom we use our DVD drives.

This app will require an administrative password. That’s because, by the design of the Mac OS X kernel, an admin password is required to access hardware. The author explains all that in the excellent FAQ.


Some may have the view that it’s unwise to get carried away with an app like this, and they’re right. Excessive driving of the fans could bring them to early failure, and there are always lingering concerns about voiding the Apple warranty. However, in an inspection of the Apple forums, I didn’t see that anyone had that problem with this app.

A judicious, careful use of this app is called for. One can sense, by feeling the air coming out of a desktop Mac’s vent whether the machine is running warm or scorching hot. The same can be said for a MacBook resting on one’s lap. If you suspect that the Mac needs just a little prodding for a short time, that’s fine. But it doesn’t seem wise to crank up the RPM by thousands and forget about it.

With careful use, this app can get you through those 100 degree sumer days and take some of the load off your Mac, especially if you have some intensive processing to do for awhile. Finally, that little bit of extra cooling could avert an expensive hardware failure if, for some reason, the Mac’s cooling system just isn’t doing a great job.


* At least for those of us in the northern hemisphere.