LATE 2012 27 inch IMAC Power Off Randomly

Hi Ryan, that would be great thank you. My iMac is at Apple right now and I will also report on what they do and if it works. I'm afraid though that they're just going to do a clean install again. They wont change parts unless they can replicate issue.

I have had the same problem with the same computer. Power goes off randomly during the day, exactly as if someone had pulled the power plug. (Checking Console gives a shutdown code of 0—power disconnected. No sign of overheating (fan is not audible) and computer will not restart using the usual methods (pressing button on back or pressing and holding button to reset). However, if the plug in the wall is pulled out then reinserted, the computer can be started normally. There are no problems with the house electricity, and the Mac has the same problems whether plugged into a power bar (with surge suppression) or the wall directly. I suspect it's a flaky power supply. Of course, it's just out of it's three-year warranty.

I still have the same problem. Made a Genius Bar appointment in March and they couldn't pin point the problem but

replaced the Logic Board, Display Panel (had a mild scratch on screen) and Power Supply regardless.. was up and running

for 3 months later.... shut down!

Going to try look at getting a new power cord (spotted a slight indentation)

Any other suggestions?

Quick update: I had my power supple replaced and it has addressed this issue. I had the service done at http://simplymac.com/ because, well, it's not packed and insane like the Apple store and I got a really thorough assessment (the guy that did my repairs reproduced the issue using diagnostic tools) and couldn't replicate after the UPS was replaced. He also ran my machine for 5 days after the power supply was replaced and couldn't reproduce it. So, the power supply was the culprit. Also, an interesting note....though the machine is "off" it's actually still running. He said he could see 3 of 4 lights on the logic board still on...suggesting that the computer was still in a semi-on state. Anyway, weird annoying problem and I hope it doesn't come back. I've been hammering this machine all morning and no issues.

After several trips to the Apple store and a local Apple repair shop, Apple replaced the logic board and power supply and so far computer is fine. Finally! So I can't say which is the issue because they replaced two things, but from the sound of it, it's probably the power supply since several other people fixed the issue after replacing that. It was frustrating to have to go to the store several times and to a local repair shop, but they were super nice and helpful every time I went in. My computer was also slightly over the warranty period and they still took care of it at no charge which they probably didn't have to.

I've got this problem with a Mid-2015 5k iMac (15,1).

Hi,

I have the same issue. Did your issue ever get resolved.

Thanks

Has anybody replace termal paste in the GPU and Core unit.

How does one lodge a complaint with Apple Support?