Imac diagnostics will not start in Mavericks
Hard drive is clicking at start up sometimes and when I come back to my Mac after it goes to sleep, sometimes I can't get a login screen. I have to manually reboot at times.
OS 10.9.5 Mavericks
Processor 2.66 GHz Intel Core I5
Memory 4 GB 1067 MHz DDR3
I'm thinking hard drive failure but can't get to the hardware diagnostics at start up.
Any help greatly appreciated.
Mark