Chosen Solution
Hi, My mac 2012 had black screen and fan yesterday. Then I powered off it and retried. This time it has loaded Catalina desktop and a few seconds later restarted. Now when I ry to power on either it shows black screen with fan sound or it desktop, restarts. I did NVRAM PRAM reset. I tried pressing D on keyboard to diagnostics but it did not load diagnostics. I tried recovery mode. It entered recovery mode but when in language selection halted and restarted. I plan to unmount, then try unplug and plug some cables inside. I appreciate any idea or suggestion. Thank you very much.
See if you missed a firmware update. Press and hold the power on button for 8 seconds and see if it starts blinking rapidly. If so, release the button and allow it to update the firmware. This will show as a oval long progress bar on your screen, just let it do its thing. If it doesn’t flash rapidly, then NeverMind.
