Chosen Solution
Hi, have had this problem for a while now, the imac just shuts off like the power was cut. Just wanted to know how to find the problem as I would prefer to fix it myself if possible. Have looked in the console but no power issues. Thanks for your help Gerry Update (02/20/2016) All the lights on etc. When I unlatch lcd light goes off. Can’t understand why it just shuts down. Don’t wanna buy a psu if it something else plus don’t wanna pay for unnecessary repairs if I can do it myself Update (02/24/2016) Still going off. All the led lights are on when supposed to be. Can stay on for a long time then go into sleep mode but when I start an app it goes off. Help with this would be greatly appreciated. Is there somewhere in the log where I would find out the problem? Update (03/03/2016) It’s a last shutdown cause the code number. I haven’t a clue what to try now. Took the logic board out yesterday. No dust on Gan or in the vents of the logic board Update (03/04/2016)
image Update (03/04/2016) Me again. Just did the full extended hardware test. No problem. Reinstalling el capitan at the moment. If my HD is dead would it still shut down while running off external drive. How do I check if fan behind. Logic board is running since I have to take it out to see. I think I might just have to give up and put some money away to buy another Mac
Most likely you have a temp issue. Have you opened the system up and cleaned it yet? I would start there. I would also recommend you install a sensor monitoring app like this one: TG Pro. If you buy the full version it will log the fans & temps upto the point of the system shutting down. So you can see if that is the issue. Paste a screen shot of the TG Pro console so we can see as well. Update (02/19/2016) If the system looks clean and the sensors all look good, it’s starting to sound like a power supply problem. What does the diagnostic LED’s doing? Now that you have the display off.
The same is happening to me. As Murphy I tried everything but nothing worked for me. One important point is that on safe mode it doesn’t happen.
I also have the exact same problem, and gave up on it since it cost too much to replace, so I’m throwing this here in case it can be of some use to others, I narrow it down to these: boot up OSX in safe mode = running fine installed Windows on it with VGA driver (NVIDIA’s) = instant shutdown remove said VGA driver from Windows = running fine so I guess it have something to do with VGA card, or the power supply can’t handle VGA in full power
Reapply thermal paste on CPU solved this problem for me. greetings, Rob van Vroenhoven / Yormac
