I'm using an iMac 11,3 (27 inch, mid 2010) with an external display (an NEC EA232WMi).

Over the past week or so (beginning just prior to 10.9.2), when the iMac's display sleeps, the external display won't stay asleep.

It keeps waking up.

I can see the power indicator repeatedly going back and forth between the "on" and "energy save" modes. When it wakes, it shows its usual message about not receiving any video input signal. The iMac's internal display doesn't (visibly) do anything at all.

It doesn't seem to be related to any apps-- if I reboot the iMac and leave it there at the login screen until the display sleeps, the same thing happens.

This only happens when the display is off but the iMac is still awake. When the iMac sleeps, everything seems normal.

If I move the external display to a different Mac (which is also running 10.9.2), the display sleeps normally, so it seems to be specific to the iMac.

I did an SMC reset and even zapped the PRAM (yes, voodoo) but they had no effect. What can I look at to figure out why the iMac keeps waking the external display?

Additional: Wondering if this might be related to an external device, I tried unplugging everything from USB. No change. Turned off Bluetooth? No change.

Update with some requested information:

  1. Console logs. All that I get is the following. In this test, the main display slept at 10:10 AM and the external display problem appeared. I let it continue until 10:16 AM. These are all the messages that appeared in Console.

    3/15/14 10:10:14.227 AM WindowServer[127]: device_generate_desktop_screenshot: authw 0x0(0), shield 0x7fa8028e4910(2001)
    3/15/14 10:10:14.253 AM WindowServer[127]: device_generate_lock_screen_screenshot: authw 0x0(0), shield 0x7fa8028e4910(2001)
    3/15/14 10:10:14.581 AM WindowServer[127]: device_generate_desktop_screenshot: authw 0x0(0), shield 0x7fa8028e4910(2001)
    3/15/14 10:16:10.580 AM WindowServer[127]: handle_will_sleep_auth_and_shield_windows: Deferring.
    3/15/14 10:16:10.582 AM WindowServer[127]: CGXDisplayDidWakeNotification [59971881496111]: posting kCGSDisplayDidWake
  2. System report "Graphics" data. Looks OK to me, let me know if you see anything that seems wrong.

    ATI Radeon HD 5750:
      Chipset Model:    ATI Radeon HD 5750
      Type: GPU
      Bus:  PCIe
      PCIe Lane Width:  x16
      VRAM (Total): 1024 MB
      Vendor:   ATI (0x1002)
      Device ID:    0x68a1
      Revision ID:  0x0000
      ROM Revision: 113-B9710C-238
      EFI Driver Version:   01.00.417
      Display Type: LCD
      Resolution:   2560 x 1440
      Pixel Depth:  32-Bit Color (ARGB8888)
      Main Display: Yes
      Mirror:   Off
      Online:   Yes
      Built-In: Yes
      Resolution:   1920 x 1080 @ 60Hz (1080p)
      Pixel Depth:  32-Bit Color (ARGB8888)
      Display Serial Number:    1X312924NA  
      Mirror:   Off
      Online:   Yes
      Rotation: Supported
      Connection Type:  DisplayPort
      Television:   Yes

Update 2

In case it helps, I uploaded a system profile of my iMac which I generated using system_profiler -detailLevel mini.

Update 3

Since @Buscar웃 is deleting their answer, I'll add these details here:

  • "Wake on Network" is disabled
  • There's no screen lock (no password required to wake the Mac)
  • All sharing services have been disabled (several were active, including screen sharing and DVD sharing, bu disabling them had no effect).

Update 4

In case it's useful, the cycle time of the wake/sleep process is 8 seconds. Meaning, if I watch the display and its power indicator, this cycle repeats every 8 seconds:

  • Monitor shows its "no signal" screen
  • Monitor goes into power save mode
  • Monitor comes out of power save
  • Repeat

Update 5

I tried doing a safe boot; this also had no effect.

Update 6

Just for completeness I also used the external display's menu system to reset it to its factory defaults, but again, this had no effect.

  • 1
    I am having a similar issue. Mac Mini 2012 with Thunderbolt display. Keeps waking up the external display. I thought I was crazy, but it seems that I am not the only one. Haven't found a solution, but thought you might want to know that it happens to me too.
    – user71886
    Commented Mar 2, 2014 at 16:05
  • I dont't own an iMac (I have a MacBook Air), but is the main display linked to the external display? What I mean is if the main display sleeps/dims, does the external display sleep? Commented Mar 13, 2014 at 21:19
  • When the main display sleeps/dims, the external display continually sleeps for a moment before waking up. That is the problem I'm trying to fix here. Commented Mar 13, 2014 at 21:20
  • Yes, I reset the SMC a couple of times. Commented Mar 13, 2014 at 22:11
  • Open System Preferences -> Energy Saving Disable "Power Nap" Report wether it still happens Commented Mar 14, 2014 at 15:15

6 Answers 6


Lets get more surgical here.

Facts are: The external monitor stays in sleep mode on another Mac. It is unknowen if that mac has a Mavericks installed.

The Console report shows nothing unusual.

The Monitor configuration profile is still to be questioned (since it identifies the monitor as TV capable?

Recommended actions:

Use the PleaseSleep app http://www.dragonone.com/products/macosx/pleasesleep/

Alternatively -Verify, Repair or replace the existing ICC profile

To verify use the Colorsync Utility and publish the current monitor profile

To repair use the ColorSyc utility and perform the repair of the external Monitors ICC

Alternatively download and install new ICC profile

New ICC profile for TFT monitor http://www.tftcentral.co.uk/icc_profiles/nec_ea232wmi.icc

  • The other Mac is also running 10.9.2. I don't know what "Television: Yes" actually means in the system report, but for what it's worth both Macs show it that way. PleaseSleep didn't make any difference (but it seems to be about making the Mac sleep, not just the display). I verified, repaired, and finally replaced the profile, still no change. Commented Mar 17, 2014 at 3:21

Have you tried either of these commands to see if some process is preventing sleep?

pmset -g assertions

pmset -g log

  • System sleep isn't the problem, nor (I think) is internal display sleep. It's just the external display. Commented Mar 20, 2014 at 0:26

It could be related to the energy saver option to "wake for network access". Just an idea.


These steps will potentially help isolate hardware/software issues. Since the monitor and cables appear to work with another Mac, apparently it's a local hardware or software issue. You can restart and perform a hardware test following these instructions from Apple (complete test takes a few hours, run overnight) by holding d prior to chime on restart, disconnecting peripherals, etc.

Testing from a clean install on a known working partition will eliminate software. If that works good news! And, I'm sorry, as you're looking at an in place reinstall best case; or clean install... this is the last thing I ever want to hear as a suggestion. :) Have you tried an OS reinstall or clean install?


Go to the system prefs -> power options then configure the sleep option.


This is a workaround.

I have a similar problem to the OP. I found that I can make the display sleep and stay asleep via the command line:

pmset displaysleepnow

In contrast, the external display wakes immediately after sleeping when I use the hot-corner method. Since display sleep problems can have many causes, my general advice is to try different methods of making the display sleep.

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