My Mac is acting very strangely…
There are all sorts of reasons your Mac might be playing up
Has your Mac started to run slowly? It’s likely there’s a process hogging CPU cycles or RAM. It could be a browser pop-under window that’s using Flash, or an application that’s run into trouble. To find out what’s causing the problem, launch Activity Monitor from the Utilities Folder in Applications. Click on the CPU tab and then click ‘CPU %’ to sort processes by the number of processor cycles they’re consuming. You should be able to see if there’s an application or process hogging the CPU. Once you’ve identified the process, Google it along with the symptoms and the model of your Mac. That should point you to relevant support articles and discussion threads on Apple’s website.
Everybody be cool
One problem, particularly with the MacBook Air, is over-heating. On hot days, in a room without air conditioning, the Air and sometimes the MacBook Pro can become so hot it seems to take steps to cool itself down. Undocumented by Apple, it appears that while the fans are kept well below their maximum speed by OS X, when it gets hot the OS implements a process – ‘kernel_ task’ – that hogs processor cycles. It deprives other apps of them, and forces the Mac to slow down to stay cool.
You can deal with this by downloading and installing smcFanControl. This allows you to set your Mac’s fans at a higher speed, thus keeping the insides cooler and reducing the need for kernel_task. It’s risky though, and isn’t a longterm solution – Apple limits the fan speed for a reason. It also significantly reduces battery life. Move the Mac to a cooler location instead, or use an external fan or an air-con unit to keep it cool.
If your cursor becomes a spinning beachball, the reason could be too little RAM and an overfull hard drive (keep at least 10% free), or an application that’s run into trouble. Fire up Activity Monitor to diagnose the problem, and, when the beachball appears, check it to see what’s causing the problem. Quit the process. If that fixes the problem, check to see if there’s an update available for the troublesome app.
A beachballing cursor could be down to too little RAM and an over-full hard drive – keep 10% of it free
Check for software updates to diagnose problems whenever they occur. Also check the login items for your account in the Users & Groups pane of System Preferences. Remove any you don’t need (but Google them beforehand, if you’re unsure what they do).
Serious hardware problems, such as a display that’s distorted, can be diagnosed by running a series of checks. The first thing to do is to reset the NVRAM (known as PRAM in earlier Macs). This doesn’t solve as many problems as it used to, and it’s unlikely to fix yours, but it’s quick and easy to do. Shut down your Mac, and then with ç+å+ P+R held down, power it on again. Your Mac will start up and then restart. When you hear the startup tone a second time, release the keys.
Still no joy? Boot into Safe mode by starting up with ß held down until you’re past the Apple logo. If the problem persists in Safe mode, it’s a hardware issue. The next step is to run a hardware test; shut down the Mac and power on with D held down until the hardware test starts. Select your language, and then choose Basic Test. Wait until it’s run through its tests and read the results. If that doesn’t diagnose the problem, run an Extended Test.
If the results confirm a hardware problem, you’ll have to take it to a Genius Bar. Check ifixit.com first, in case you can repair it yourself.