After I did my last post on 4 Months After Switching Over From Windows To A Mac, I got asked about how I actually ran the Apple Hardware Test on loop mode.
To do so, you’ll need the Applications Install DVD that came with your Mac. This is the one that has a little block of text in the upper right corner that says to press D to launch the Apple Hardware Test when starting up.
Follow those instructions, and you’ll come to the Apple Hardware Test screen. After selecting your language, press Ctrl+L to go into loop mode. Remember to check Extended Testing too.
This test is a pretty good diagnostic tool for finding problems with your hardware. The bundled TechTools utility test in Mac OS just doesn’t do anything for intermittent, hard-to-find hardware errors – I mean, come on, it finishes in 5 minutes. This hardware test will take you at least an hour to finish just one loop. I highly recommend running it overnight while you sleep so that it can complete 5-7 loops. This so that you can know that it did a comprehensive test, and that any intermittent hardware faults (such as faulty RAM) can be triggered.
Now if the test does find an error, you’ll get a prompt about the problem it found. It could be for a variety of reasons, so write down the error and do your research afterward. If the test didn’t find an error, it may mean your system is fine, or it may be because the hardware test did not find the problem. Remember: This test is good for superficial errors, but it’s known to be unable to test for and detect the entire gamut of hardware issues.
To stop the Extended Test and exit Loop Mode, press Cmd+. (that’s a period). I found that pressing the Stop Test button didn’t work that great and the program didn’t seem to respond to it, but that shortcut worked immediately.