My iMac does not sleep after install of El Capitan

Hello, I have the same issue. The display turns off, but I can hear my Imac is still working. It happened just after I upgraded to El Capitan. Restart didnt help. Don't know to fix. I installed the latest version of OS X from app store. My Imac is late 2012 27". Didn't find any solution for this problem

Hi, I can partly confirm this behavior after installing El Capitan. Even System fell in sleep when I force it to do, it does not happen automatically anymore.

iMac (27", mid. 2011, running SSD on Thunderbolt, OS X El Capitan 10.11)

Regards

I have a late 2013 27" iMac and I'm having the same no sleep problems after installing El Capitan 😟

If I set my Energy Saver to 1 min nothing happens, I don't even get a blank screen! I've disabled Wake for Network Access, and Power Nap nothing works..

I've never had this issue until up until El Capitan, guess there are a few bugs to be worked out...

Sigh....

Hi,

seems I got it fixed now ... after some google ... I did the general steps like SMC, NVRAM Reset. I also deleted Macintosh HD > Library > Preferences > System Configuaration > com.apple.PowerManagement.plist.

Afterwards it worked ... what it still does.

You can also check what devices prevent sleeping with command:

pmset -g assertions

Good luck + regards!

<Edited by Host>

Funny... Now that I've rebooted my machine a number of times all of a sudden it'll now sleep without issue, power nap even works!

I haven't changed a thing!

Once again *BUGS* hahha..

Hopefully everyone else's machine came to their senses as well!

Thanks for that command, very helpful!

-KC

I've rebooted my iMac 2011 many times (El Capitan), but still no sleeping ...

In my case, after

pmset -g assertions

it says

Idle sleep preventers: IODisplayWrangler

Does anyone know what this means? Or - even better - how to solve it?

Having the same issue (mid-2011 iMac, 19"). Won't sleep even after manually trying and/or will sleep and keep re-waking after a few seconds.

I found the same IODisplaywrangler item as above. Cure?

This seems to apply to more hardware. Not just iMacs. I am on a mid 2012 MBP, and it will not sleep UNLESS I close the lid. That seems to trump it.

I have tried quite a few things, resetting SMC, resetting print system, removing the sleep image, deselecting BT looking for a keyboard and mouse on startup, removing shares (had none..but someone suggested that..) etc.

IODisplayWranger is still preventing idle sleep though. Seriously hope someone comes up with some kind of solution.

One theory I had was that the optimization going on after installing El Capitan was doing this..however I upgraded the day it was released, and I have had the MBP on for quite some time since. If it is still doing some background magic I wish it would tell me..

I will try the "reboot a bunch of times" trick now.. Oh Joy! 🙂

Same here - iMac mid 2011. Not even "PleseSleep" can make my iMac sleep. And to put it to sleep with the "Sleep" under the Apple menu does not make it sleep. Nothing makes my iMac go to sleep. I also get the "IODisplayWrangler" when running the command "pmset -g assertions".

This must be a bug in El Capitan.

Same issue : mid 2011 iMac 27". Doesn't won't to sleep anymore since El Capitan.

And I can confirm that the recent El Capitan update this week did nothing to improve the situation.

Reset PRAM did help with me ... for now, at least.

But, El Capitán is een version with a lot of small, but irritating bugs.

Also afflicted with the same problem on my later model iMac. I'll try the PRAM reset and see if it helps me. It's interesting to see this affecting many late-model iMacs.

Tried the firmware resets and it had no effect on the non-sleep problem for me. But if one wants to try it, here are the instructions.

Time to sit back and hope Apple addresses this in an update very soon. 😟

How to do an SMC Reset:

https://support.apple.com/en-us/HT201295

- Shut down the computer.

- Unplug the computer's power cord from both the wall and computer.

- Wait 15 seconds.

- Attach the computer's power cable.

- Wait another 5 seconds and press the power button to turn on the computer.

How to do a PRAM / NVRAM Reset:

https://discussions.apple.com/docs/DOC-3603

- Shut down the computer.

- Locate the following keys on the keyboard: Command, Option, P, and R. - You will need to hold these keys down simultaneously in step 4.

- Turn on the computer.

- Press and hold the Command-Option-P-R keys. You must press this key combination before the gray screen appears.

- Hold the keys down until the computer restarts and you hear the startup sound for the second time.

- Release the keys.

" Reset PRAM did help with me ... for now, at least. "

But after a few days it was the same old trouble.

More is that since El Capitan is on the throne,

I do suffer a lot of problems and crashes.

Apple, where are you ?