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Question: Mountain Lion won't wake from sleep

I have a mid-2011 Macbook Air 13". Since installing Mountain Lion (and immediately upgrading to the latest SMC firmware update), the machine will not wake from sleep. When I close the lid, it goes to sleep fine. Upon opening the lid, the screen turns on (apple logo glows on outside of monitor, faint glow from screen), but it remains black, nothing ever appears. Only way to fix this is to hard-reset the machine. Machine was fine under Lion, most definitely related to that upgrade, but still unclear how.

I've tried 3 different things that I found in other forums, hoping to consolidate them here.

1. Reset SMC (

2. Reset PRAM (

3. Set the startup volume specifically in the startup disk system preference.

None of these have fixed my issue.

Is this issue more widespread? Seems that others are reporting it on a variety of SSD macs, but that could be a red-herring.

NOTE: this was an upgrade, not a clean install. I will attempt a clean install onto an external bootable drive in a few days to see if this is a hardware/SMC issue, or a Mountain Lion issue, or a 3rd party software conflict problem that crept in during my upgrade.

Any other advice out there?

MacBook Air (13-INCH, MID 2011), OS X Mountain Lion

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Jul 28, 2012 8:08 AM in response to wkoffel In response to wkoffel

Additional info, the machine works fine from a "shallow sleep", but not when hibernating.

I changed the hibernate mode to RAM only with:

sudo pmset -a hibernatemode 0

and it seems to wake from sleep fine. Of course, this risks running the battery down since the contents of memory aren't saving safely out to disk, so it's not a long-term acceptable solution.

Jul 28, 2012 8:08 AM

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Jul 28, 2012 3:54 PM in response to wkoffel In response to wkoffel

I have instaled "SmartSleep" app and change hibernate settings to sleep only. I Think it has the same effect of your command. My Imac 27 is working better without freezing.

I had the same issue when i did the upgrade from Snow Leopard to Lion and used the same software. When I returned to sleep+hibernate everything was fixed.

I think there is something corrupted in /Library/Preferences/SystemConfiguration/ when you upgrade.


My pmset -g output is:

Active Profiles:

AC Power -1*

Currently in use:

hibernatemode 0

halfdim 1

womp 0

networkoversleep 0

sleep 30

powerbutton 0

ttyskeepawake 1

hibernatefile /var/vm/sleepimage

autorestart 0

disksleep 10

displaysleep 1

Jul 28, 2012 3:54 PM

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Jul 28, 2012 3:58 PM in response to paulofromnew york In response to paulofromnew york

So, after I confirmed that worked, I wanted to test more variables, so I set hibernate mode back to 3 (safe sleep, save to RAM and disk).

And the issue has gone away for me! At least for now, for a few hours of playing, sleeping, letting it sit on both power and disconnected.

I will update this ticket again if the issue creeps back.

Jul 28, 2012 3:58 PM

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Jul 29, 2012 11:33 AM in response to jefffromjamesville In response to jefffromjamesville

Well, Jeff. Changing the hibernate mode is a pretty well-documented and "safe" thing to do. There are lots of instructions online that will step you through it, only takes 10 seconds and may well solve your problem.

Theory in this thread from ellisonjay that the hibernatemode is also a culprit for him. p123456

I really wish I'd checked to see what my hibernatemode was set to when I was having problems before I manually reset it. But this simple fix has been working for a couple days now, so I'm pretty optimistic it was related to those pm settings.

Jul 29, 2012 11:33 AM

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Jul 29, 2012 4:45 PM in response to jefffromjamesville In response to jefffromjamesville

This should help you Jeff:

`man pmset` at the terminal.

"We do not recommend modifying hibernation settings. Any changes you make are not supported. If you choose to do so anyway, we recommend using one of these three settings. For your sake and mine, please don't use anything other 0, 3, or 25.

hibernatemode = 0 (binary 0000) by default on supported desktops. The sys- tem will not back memory up to persistent storage. The system must wake from the contents of memory; the system will lose context on power loss. This is, historically, plain old sleep.

hibernatemode = 3 (binary 0011) by default on supported portables. The system will store a copy of memory to persistent storage (the disk), and will power memory during sleep. The system will wake from memory, unless a power loss forces it to restore from disk image.

hibernatemode = 25 (binary 0001 1001) is only settable via pmset. The sys- tem will store a copy of memory to persistent storage (the disk), and will remove power to memory. The system will restore from disk image. If you want "hibernation" - slower sleeps, slower wakes, and better battery life, you should use this setting."

[repost from:]

Jul 29, 2012 4:45 PM

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Jul 30, 2012 9:52 PM in response to wkoffel In response to wkoffel

I am having a similar issue. At first, my alarm clock 2 application would not wake the Mac from sleep. Help desk had me reset the computer and RAM, and then it worked. Now my keyboard will not wake the Mac from sleep, only my mouse. Please let us know if there is a fix for this, it is very frustrating.

Jul 30, 2012 9:52 PM

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Jul 31, 2012 8:00 AM in response to wkoffel In response to wkoffel

Hi Guys

Yep, I have a similar issue but with an added twist which is that my 2011 MBA seems to also wake itself up occasionally since I upgraded to Mountain Lion.

Several times now I have put it to sleep (either by closing the lid or selecting 'sleep') and waited for the lights to go out and everything quiet. Then I open my bag some hours later to find it red hot and fans going like crazy. If I then open the lid, the machine does not come back up fully. Maybe I see the mouse cursor but nothing else. Then I need to hold the power button until it goes off again.

Taking a look with pmset I see that hibernate mode is set to 5. I have never modified this, so this is how my machine came. Interestingly this is not one of the values described as 'recommended' by Ellisonjay and is allegedly not the default shipped value for this machine (should be 3).

According to this article:

Mode 5 is fully hibernated mode (no power to RAM) which for a machine with SSD seems to make sense as the time penalty of reading back from SSD should be not so large.

So, yes, I want hibernate mode to work but, in the meantime, I hope mode 3 will at least stop my machine from waking up and frying itself inside it's case.

Jul 31, 2012 8:00 AM

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Jul 31, 2012 8:05 AM in response to Boris2012 In response to Boris2012

Interestingly, my iMac is sleeping "deeper" than ever, it's just hard to wake it up! I sleep next to my computer, and it seems like it's doing a better job of turning off my external hard drive (set on auto mode) and is quieter throughout the night. It's just really hard to wake it up, and when I do, the clock is wrong for about 10 seconds while it is waking up.

Jul 31, 2012 8:05 AM

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Jul 31, 2012 2:32 PM in response to wkoffel In response to wkoffel

Just a quick follow up.

I've now changed hibernatemode from 5 to 25 and, so far, it works just fine.

So, this is just going directly into full hibernation (no power to RAM). This is the behaviour I have always had with my MBA since out of the box. For an SSD based system, I don't see the need for anything more complicated than that. It's the most power efficient and resume time from hibernation is just 3-4 seconds for me anyway.

Jul 31, 2012 2:32 PM

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Jul 31, 2012 3:28 PM in response to dselevan In response to dselevan

I was just at apple store and genius said that happened to him also. He said to tell the computer not to put hard drives to sleep in power settings.

Jul 31, 2012 3:28 PM

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Question: Mountain Lion won't wake from sleep