Chosen Solution
Hello, my iMac 27in 2011 model started having issues with display. I was looking all over the internet trying to find a solution, but nothing worked or was exactly the same problem as mine. The issue: When I turn the iMac on, everything works fine except the internal screen is black. External screen works fine. When I load into the macOS, and when I change the internal screen resolution (I have to do it multiple times, maybe like 20x switch between two different resolutions), the internal screen turns on and works normally until I turn the computer off, then I have to repeat the whole procedure. I tried all the easiest stuff such as reset SMC and PRAM, Recovery and Safe mode etc, using a flashlight.. Now I tried replacing LVDS cable, but also did not make any difference. I also checked the diagnostic LEDs: When I turn the computer on, 1, 2 and 3 are on, 4 is off, until I change the resolution (as described above) and the display turns on. Then the LED 4 is also on (obviously). But when I put the display to sleep by using a keyboard shortcut (Control+Shift+Eject), the internal screen turns off as it should, but also the LED no.4 turns off - is this normal behaviour? Also what I noticed is when I use the keyboard shortcut to put the display to sleep, in the past the screen was slowly dimmed until it was off. Now, when I press the keyboard shortcut, the display just goes black instantly. This machine works perfectly otherwise, so I don’t want to put it away. If you have any suggestions, that would be highly appreciated. Thanks
I’m suspecting your PRAM battery is failing. Go into the Date & Time settings in your Preferences. Unlock the settings and turn off Set date & time automatically. Now let the system sit turned off for the night in the morning check the data & time is it correct? If it’s not the battery needs replacement.
