Late 2012 iMac locking on Sleep

Ok. Try moving all the cables/ports/wires (such as the wired mouse and keyboard) to the opposite side of the large cable that is plugged into the middle back of the iMac.

I'm not sure if it will work (worked for me though and a few other people), so also try looking at how many minutes it takes to go to sleep and the preferences once it does go to sleep. Your problem seems to be a 'one of a kind' but as you said, "There must be a solution."

When it's asleep, try awakening it by pressing the power button (no longer than two seconds, or the computer will restart).

If none of these moves work, I believe you should definetely seek out an Apple Specialist. (You should still have that warentee, since it works for a whole year.)

Hope I've helped you!

-Sanga1999

If it is a Late 2012 27" iMac then it is Brand New. Take it back for a full refund and get one that works correctly. Or some other make model of computer that works correctly.

After Re-Reading, Actually reading your full first post, you may be asking to much of the system. RAID 1 with an external and putting the drives to sleep may be more then the system can take. You do know that it takes a period of time for the system to Wake external drives after the system comes out of sleep mode? that is more then likely part of your problem. The system hangs because the external is still asleep and when the system hangs it never wakes up the external.

I think the RAID is the problem, not the computer. Read Shootist.

Well, just spend a little more time now:

If you did not already, do the SMC reset.

If you did not already, do the PRAM reset.

I'd like you to copy/paste the following 3 commands in Terminal:

sudo pmset -a hibernatemode 0

sudo nvram "use-nvramrc?"=false

sudo rm /var/vm/sleepimage

then quit Terminal, restart the mac.

do you have the same issue?

Hey Ktulu9876, you're not alone, same story here.

Brand new iMac Late 2012 27 Screen, 3,4 Ghz i7, 16Gb Ram, 3TB Fusion, 2GB Graphic Card.

When it goes to sleep it never wakes up again after, i have to unplug the cables and plug them in again and then it works.

Simply unacepptable, talked to the Apple Care Hotline already, they have no clue what I was telling them,

the person from the hotline did some tricks, thore resets which are told above included but none helped.

BUT seems like the 21 also had a sleeping problem which is why the brought out an "EFI Update" on the 17.12. but ONLY for the 21 inch.

I am also very confused if I should return the iMac or wait if there will be also an EFI Update for the 27inch.

Looked all over the Internet if somebody else has the same problem but your post was the first one i found about this MAYOR problem.

Also my old usb hub (2.0) was not useable anymore, i had to get a new 3.0 hub.

Seems like this thing just needs to get sorted out but not from customers, Apple needs to take care of this.

What do you think?

I have a similar problem with my late 2012 27" iMac.

If left alone, it goes to sleep, but then it can't wake up. Sometimes if I hit the keys on the keyboard enough, it powers up (complete with the startup chime); other times I have to reach behind and turn it on again.

At first I thought some of the kids were doing me a favour and turning it off. No such luck, it's doing it by itself.

My temporary solution is to make sure the computer never sleeps.

The firmware update 2.0 for the 21" iMacs sounds like it addresses issues like this, but apparently won't work for 27" iMacs.

iMac

27-inch, Late 2012

Processor 3.4 GHz Intel Core i7

Memory 8 GB 1600 MHz DDR3

Graphics NVIDIA GeForce GTX 675MX 1024 MB

Software OS X 10.8.2 (12C2037)

Similar issue here on my late 2012 27" iMac.

If left alone, it goes to sleep. It does not wake up, instead it reboots. After a reboot the bluetooth mouse will not reconnect until I switch the mouse on/off. Same with the magic track pad.

Issue has all the symptoms of bugware...

Yeah similar issue here... Late 2012 iMac full spec 27". Turns itself off and on again after about an hour in sleep mode, had it 1 day and already done this about 3 times? Do I call for a replacement? So annoying as its for business and now I am losing out on time/work as cant rely on this for work...

Are people still having issues?

I found my issue. It is the memory modules from crucial that make it crash. I upgraded the internal memory with 2x8GB modules from crucial. An apple upgrade kit. When I put them in, the sleep issue is there. When I take them out the problems is gone. It is very consistent. I tried swapping the modules to a different memry bank, but that made no difference.

I now contacted crucial and will post back here how this story continues.

Anyone else with the same issues that did a memory expansion?

McHerb you legend... that's exactly what I found out, now you have confirmed it, I have rectified my problem....

LISTEN OUT ALL MEMORY UPDATERS

I have spoken with Crucial, basically you need to have the exact and correct version of the memory you buy off of them, I simply searched and bought what looked right before, but now after calling them, despite same spec memory (I bought 2x16GB kits of memory), they have a specific one that works with Apple only.

So if you are having the sleep problem, it is not your iMac (well for memory updaters potentially), it is the memory is not the right sort, in my case anyway.

I have just re-ordered the correct one's from Crucial... 2 x 16GB kits (2 x 8gb sticks) to make it 32GB and the memory code from Crucial for this product is: CT2C8G35160BMCEU. Or just give them an actual call when ordering to make sure you get the right kit.

They are sending me a new kit and they think this is soley the problem why I was having the SLEEP issue, not because my iMac is faulty.

Hope this helps some people rectify their problems?

In hudreds of threads here in this forum, it is said again and again, that you have to buy the exact specification of RAM. Not exact specifications can cause a number of issues, the most important one is Kernel panics.

On the Crucial site is a very precise configurator, so buying "...what looked right before..." is not enough.

not this time Lex. I have the right modules, specially for late 2012 iMac, all the right specs. Tech support crucial was like.....uhhhh.....uhhhhh......shoot!

The ones I have in my iMac are: CT3650279

These are the right modules with the specs:

DDR3 PC3-12800 • CL=11 • Unbuffered • NON-ECC • DDR3-1600 • 1.35V • 1024Meg x 64 • Part #: CT3650279Apple iMac 3.4GHz Quad-Core Intel Core i7 (27-inch, Late 2012)

Still they cause an issue. Will keep you updated on progress with crucial Tech Support