Ever hear a Mac's desktop fans go into overdrive under normal operating conditions? Or felt a Mac laptop go from a normal temperature to a more-than-toasty lap roaster in under a minute? Those are times when a Mac was running hotter than it should have been.
What are the long-term effects of overheating on a Mac? Beyond warmer temperatures and additional noise from the fan working overtime to cool its operating environment, you can expect to see slower performance. Long term, damage to core components may occur--for example, heat can affect battery life on a laptop.
While current hardware uses internal temperature sensors to shut itself down before parts become dangerously overheated, it still helps to keep an eye on things before your Mac gets too hot. To this end, Bjango's $16 iStat Menus application is excellent, with a temperature gauge in the Finder's menu bar as well as readouts for your incoming and outgoing Internet bandwidth, hard-drive capacity, and RAM and CPU usage. iStat Menus told me that my MacBook Pro's temperatures swung between 130 and 177 degrees Fahrenheit while I was installing World of Warcraft, so the software gives you an idea of just how warm things can become under the hood of your Mac.
Your Mac is not alive, but where heat and airflow is concerned, it's essentially a breathing thing--give your Mac some room to breathe.
If it's a desktop machine, try to keep it at least 18 inches from the wall for the fan to take in air, circulate it, and then expel it as necessary.
If you love flopping on the bed with your MacBook and Netflix before bed, try to clear some room for ventilation to keep things cool. Netflix or anything that uses Adobe's Flash Player tends to add a lot of overhead to your Mac's workload, requiring more out of the fan system.
Update the firmware
Yes, a "firmware update" sounds a bit scary and technical, but it's generally for the best. If your fan's going into overdrive for apparently no good reason, be sure to run OS X's Software Update to ensure that you're running the latest firmware for your machine (OS X will find the most current version), and if you aren't, download and install it.
It shouldn't take more than a few minutes, and with fan and cooling fixes incorporated into the updates, this sometimes takes care of the problem.
Though computer fans get the air circulating, they also pull in dust and don't always get rid of all of it. Dust bunnies accumulate and have wild dust bunny parties, and since everyone loves a party, more dust bunnies appear, and the build-up makes it difficult for the fans to keep the system cool.
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