Mac Running Hot? Control the Fans

| How-To

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.

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Lee Dronick

I have found that a small desk fan can help break up the heat bloom around a Mac, or Pc. Sure warm air rises and cooler air moves in, but extra help is nice.

Stan Winstone

That sounds like a great way to fry your machine/void your warranty…

John Martellaro

Stan: Perhaps I should have added some strong cautions in the article grin


a small desk fan can help break up the heat bloom around a Mac

I add a roughly 1” high block at the back to let the fan blow underneath. Plus, it puts the keyboard at an angle more comfortable for me.

Lee Dronick

I add a roughly 1? high block at the back to let the fan blow underneath. Plus, it puts the keyboard at an angle more comfortable for me.

I assume you are using a MacBook, I too have my MacBook raised up about an inch. I am using my father’s old engineer’s scale and it is the perfect length. Kind of an in honor sort of thing.

On an iMac make sure you clean the circular vent on the back, just below the stand’s hinge. It is easy to miss that.


I assume you are using a MacBook

You assume correctly. I failed to specify that for my MBP 15”.


On an iMac make sure you clean the circular vent on the back, just below the stand?s hinge. It is easy to miss that.

Thanks for the tip.  I had not noticed the small opening before.

Lee Dronick

Thanks for the tip.? I had not noticed the small opening before.

It is a hassle to vacuum out. I use a cardboard tube from a roll of paper towels as a vacuum hose extension. Tape off the end and cut a hole in the side of the tube so that you can press it against the vent. Occasionally I will remove the bottom of the iMac and vacuum that opening. Lint and such will of course contribute to overheating.

Dorje Sylas

I have no qualms about using smcFanControl. Apple made a design choice for quietness over cooling and it occasionally bit me in the rear with my Mac Pro before I started controlling the fans. I noticed most often when in Windows XP through BootCamp, the fans just did not want to seem to speed up at higher temperatures. Especially when running graphics intensive PC games. It’s some of the few times I’ve had a Mac shut off on me due to heat overload.

I’m also coming near the end of my Apple Care and I’d rather have to replace a fan then have the processor or motherboard crisp on me due to Apple’s choice not to deal with the heat issues in their products.

A good tip for using smcFanControl is to create multiple fan profiles and know which of your Apps will tend to put heavy loads on CPUs and GPUs. That way you can self-regulate without having to crank your fans up to max every time you turn it on.

Until Apple starts heat testing their computers in the Arizona summer with intensive graphics use, I’ll decide what’s the best speed for my computer’s fans.

John Martellaro

Reader Sylas:  I think that’s a very sensible approach. It nicely punctuates the spirit of the article. Thanks.

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