27 iMac (2012) crashes and requires smc reset to turn on

Apple needs to be honest and recall these Macs.

I expected better of Apple than this.

They appear to be hoping that the affected users like us will just give up.

i took my imac 27 late 2012 apart and changed the thermal paste. I had read someone say that was the reason for the heat problems and would fix the reset problems. I had installed macs fan control and could see the temp spiking just before the resets. Alas no luck.

When i put the computer back together i attached the monitor screen with masking tape instead of double stick tape in case the paste didn't work. Then i saw this thread and decided to try the new power supply. Amazon sells the power supply (Liteon) for $65.97 with shipping. So i ordered it and got it today. Just installed and stress tested it. I test with high def video files at full screen. These seem to spike the gpu temps on macs fan control. Anyway it seems to be working. If i see another shutdown i'll report back.

My computer is now failing during shut down.

When I next try to start the computer up nothing happens. I have to unplug it, wait a while, plug it back in and then start the computer up.

It might be time to replace the Delta PSU with the Liteon.

Mine's been fine since I did that!

Had this problem for almost a year with random shutdowns as much as twice a day. 1st trip to Apple store came back with the usual 'we couldn't find anything wrong with it'. Just had a 2nd trip to the Apple store and told them that I believed it was the PSU at fault and they replaced it. Computer was ready 24hrs later. This was almost 3 weeks ago and haven't had a single shut down since. I'm keeping my fingers crossed.

Also, Apple didn't charge.

Reporting back:

zdz80 wrote:

i took my imac 27 late 2012 apart and changed the thermal paste. I had read someone say that was the reason for the heat problems and would fix the reset problems. I had installed macs fan control and could see the temp spiking just before the resets. Alas no luck.

When i put the computer back together i attached the monitor screen with masking tape instead of double stick tape in case the paste didn't work. Then i saw this thread and decided to try the new power supply. Amazon sells the power supply (Liteon) for $65.97 with shipping. So i ordered it and got it today. Just installed and stress tested it. I test with high def video files at full screen. These seem to spike the gpu temps on macs fan control. Anyway it seems to be working. If i see another shutdown i'll report back.

Its been 10 days since replacing the power supply. Everything works and no shutdowns. The old supply was a Delta.

I have looked at the old supply for problems(puffed caps) and didn't see any. I have since looked harder and one of the 1500 uF 16volt caps looks different. It has very faint signs of puffing.

I have no idea how long the new supply will last and am actually thinking of buying a spare.

Surprise, surprise.

iMac 27" 2012 3.4 I7 1 Gb Fusion 24 Gb Ram running El Capitan

Last week it just turned off. Thought it was electricity interruption. Nope.

Had to turn off at the wall to restart.

Has been randomly turning off all week. Can get it to run for a few days and then it all starts up again. Today has been the worst. Lucky to get 20 minutes out of it before a shutdown. So far 6 times today and it requires a few minutes with the power off at the wall before it will boot.

Initially tried UPS but no go, looked at fan speeds and temperatures. Nothing extreme. Tends to crash around 54 degrees Celsius on the GPU. Have tried with boot disk running Yosemite and Bootcamp Windows. All shut down so not software related.

I have located many posts on forums explaining the same issues. Console indicates "0" as the cause which follows the trend.

Am going to approach Apple for a response before I endeavour to replace the power supply.

After reading through the whole 31 depressing pages of this thread i thought i'd add my name to the list.

I have the same exact problem as the rest of you, the imac cuts off, need unplugging for a while before it will work, then does it again etc.

Mine is the 3.2 i5 processor and have 24gb RAM

I use mine mainly in windows via a boot camp partition so it's happened mainly there although it has done it in OSX too.

I've used windows 7 and 10 and the last couple of varieties of OSX while this has been happening.

(I've also never had Safari installed in Windows and never use it in Mac OS in case anyone actualy believed that could be the cause)

I haven't contacted Apple about the issue yet, as with the unplugging workaround and the hassle of dragging a 27" computer through a shopping centre i've just been putting it off.

My first thought when it started happening was the PSU and that still seems to be the most likely cause.

This is my first mac computer and will most likely be my last.

Same issue here as well. I took the machine to a certified tech, they couldn't replicate the issue. Once I had the machine home and running it started right back up. Brought it back in and they were able to replicate the problem. They replaced the PSU and I went home happy as a clam. Within three weeks the problem was back and that's when I started digging for more info and wound up here.

I've been on a mac for nearly 15 years and for the first time feel truly let down. Unfortunately I'm not going to move my workflow to a PC and am faced with swallowing another 3k + for a new home machine.

So, is it too soon to determine if the Liteon power supply may be a answer to the problem ?. Have ordered one and decided there is nothing to lose in having it fitted.

Hey, Has apple responded at all? Same issue here.

Also how has Apple not noticed a thread with 31 pages, and almost 50,000 views.

someone tried to replace the CPU?

is it possible that the problem is only with higher i5 and i7 and not the basic i5 and i7???

Same model here. Had psu changed (also logic board and a new hard drive) in March. It's now begun to fail again. I'm getting less than two hours out of it before the power fails. Disappointing to say the least. I also can't get an appointment at the local Apple store which is even more annoying than the fault and that's saying something.

Same issue over here : iMac@3,4Ghz i7. Computer that cost 3000€ 3years ago.

A friend had the same issue, and his PSU was a LiteOn 😟

So i am not sure this is coming from the Delta PSU... unless he is an exception.