Sometimes your Mac may suffer from glitches or some unwanted systematic behaviour. This could be due to many things and the list is almost endless.
It could be hardware or software based but working that out too can also be difficult. I have recently been asked to diagnose an iMac’s strange behaviour and sent a list of possible solutions to the member. I thought that I would try to compile some possible diagnostic tests that members can try and, in doing so, help work out and perhaps even solve their Mac’s problems.
I will list each method using letters then numbered steps within it if required.
Here is how...
Also note: If you have a wireless or Bluetooth keyboard then the tests that involve holding down keys as you start your Mac may not work as these devices are not enabled until the end of the boot process. In this case you will need a wired USB keyboard.