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In sleep mode, my iMac screen lights up with a black screen and then off.

This happens as a regular cycle of about 10 seconds over and over. Screen On, Screen Off. This is a mid-2011 21.5 inch 2.5GHz i5 with 8GB ram. OS X 10.10.2. I have tried unplugging/flashing the memory. I have unplugged all peripherals and made sure there are no bluetooth devices (other than the keyboard) in range. Can't find this particular condition anywhere else on the forum. Thanks in advance.

iMac, OS X Yosemite (10.10.2), Mid 2011, 21.5 inch

Posted on Mar 31, 2015 5:30 AM

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Question marked as Best reply

Posted on Apr 2, 2015 1:59 PM

Greetings KSchullerToronto,


I understand your iMac is entering and exiting sleep repeatedly. That does sound troublesome. The following article provides troubleshooting steps which you may want to explore:


OS X Yosemite: If your Mac won’t go to or stay in sleep


If your Mac won’t go to sleep or stay in sleep, here are some possible solutions:

If your Mac doesn’t go to sleep when you expect it to, or if it wakes up unexpectedly, you may need to change your sleep preferences. If that doesn’t work, something may be waking your Mac.

  • Check your system’s sleep settings:

    Make sure the sleep settings are set the way you want. To view sleep settings, choose Apple menu > System Preferences, then click Energy Saver.

    Drag the slider to set the amount of time that should pass before your computer goes to sleep. For more information, see Schedule a time for your Mac to turn on or off or go to sleep.

  • Check your system’s network access setting:

    Other users may be waking your Mac remotely to use its shared resources. If you don’t want this to happen, choose Apple menu > System Preferences, then click Energy Saver.

    Then deselect “Wake for network access.”

  • Check your system’s Bluetooth settings:

    Bluetooth devices can wake your Mac. If you don’t want a Bluetooth keyboard or mouse to be able to wake the Mac, choose Apple menu > System Preferences, then click Bluetooth.

    Click Advanced, then deselect “Allow Bluetooth devices to wake this computer.”

  • Check your system’s sharing preferences:

    People using shared services on your Mac can prevent it from sleeping. For example, they may be using a printer connected to your Mac or accessing shared files stored on it. To check to see that you’ve enabled the right set of sharing preferences, choose Apple menu > System Preferences, then click Sharing.

    Then turn off any services you don’t need to use by deselecting the On checkbox next to the service.

  • Check to see if something else is waking your Mac:

    Check any of the following:

    • Unexpected keyboard presses or mouse and trackpad clicks: Key presses and mouse or trackpad clicks can wake your Mac. If your Mac wakes when you’re not present, something may be pressing the trackpad or mouse button, or keyboard keys.

    • Apps: Apps that access a disk can keep your Mac from going to sleep. For example, iTunes accesses your disk to read the songs it plays, and DVD Player accesses the optical disc drive to play movies.

    • Spotlight indexing: If Spotlight is indexing your hard disk, your Mac won’t go to sleep. Click the Spotlight icon User uploaded file on the right side of the menu bar of your Mac to see if Spotlight is indexing. Indexing can take several hours, depending on the number of files on your Mac.

    • Connected storage and devices: Malfunctioning USB, FireWire, and Thunderbolt storage and devices may keep your Mac from going to sleep. Disconnect those devices and see if your Mac goes to sleep. If it does, reconnect each item, one at a time, until you find the one that’s malfunctioning. Contact that device’s manufacturer for more information.


If these steps above provide no results, your iMac may need to be serviced. The following link should help you get started with the process and has links with additional information on topics such as warranty and service pricing, battery replacement, and express replacement service.


Apple - Support - Service Answer Center





Thank you for contributing to Apple Support Communities.


Best,

Bobby_D

2 replies
Question marked as Best reply

Apr 2, 2015 1:59 PM in response to KSchullerToronto

Greetings KSchullerToronto,


I understand your iMac is entering and exiting sleep repeatedly. That does sound troublesome. The following article provides troubleshooting steps which you may want to explore:


OS X Yosemite: If your Mac won’t go to or stay in sleep


If your Mac won’t go to sleep or stay in sleep, here are some possible solutions:

If your Mac doesn’t go to sleep when you expect it to, or if it wakes up unexpectedly, you may need to change your sleep preferences. If that doesn’t work, something may be waking your Mac.

  • Check your system’s sleep settings:

    Make sure the sleep settings are set the way you want. To view sleep settings, choose Apple menu > System Preferences, then click Energy Saver.

    Drag the slider to set the amount of time that should pass before your computer goes to sleep. For more information, see Schedule a time for your Mac to turn on or off or go to sleep.

  • Check your system’s network access setting:

    Other users may be waking your Mac remotely to use its shared resources. If you don’t want this to happen, choose Apple menu > System Preferences, then click Energy Saver.

    Then deselect “Wake for network access.”

  • Check your system’s Bluetooth settings:

    Bluetooth devices can wake your Mac. If you don’t want a Bluetooth keyboard or mouse to be able to wake the Mac, choose Apple menu > System Preferences, then click Bluetooth.

    Click Advanced, then deselect “Allow Bluetooth devices to wake this computer.”

  • Check your system’s sharing preferences:

    People using shared services on your Mac can prevent it from sleeping. For example, they may be using a printer connected to your Mac or accessing shared files stored on it. To check to see that you’ve enabled the right set of sharing preferences, choose Apple menu > System Preferences, then click Sharing.

    Then turn off any services you don’t need to use by deselecting the On checkbox next to the service.

  • Check to see if something else is waking your Mac:

    Check any of the following:

    • Unexpected keyboard presses or mouse and trackpad clicks: Key presses and mouse or trackpad clicks can wake your Mac. If your Mac wakes when you’re not present, something may be pressing the trackpad or mouse button, or keyboard keys.

    • Apps: Apps that access a disk can keep your Mac from going to sleep. For example, iTunes accesses your disk to read the songs it plays, and DVD Player accesses the optical disc drive to play movies.

    • Spotlight indexing: If Spotlight is indexing your hard disk, your Mac won’t go to sleep. Click the Spotlight icon User uploaded file on the right side of the menu bar of your Mac to see if Spotlight is indexing. Indexing can take several hours, depending on the number of files on your Mac.

    • Connected storage and devices: Malfunctioning USB, FireWire, and Thunderbolt storage and devices may keep your Mac from going to sleep. Disconnect those devices and see if your Mac goes to sleep. If it does, reconnect each item, one at a time, until you find the one that’s malfunctioning. Contact that device’s manufacturer for more information.


If these steps above provide no results, your iMac may need to be serviced. The following link should help you get started with the process and has links with additional information on topics such as warranty and service pricing, battery replacement, and express replacement service.


Apple - Support - Service Answer Center





Thank you for contributing to Apple Support Communities.


Best,

Bobby_D

Apr 14, 2015 7:13 AM in response to bobby_d

Thanks for your suggestions. After all the recommended fixes proved unsuccessful, I brought it in for service. It appears to be a software issue as the problem only happens when logged in to my account. Logging in as a guest stopped it, as did operating the machine from the technicians HDD.

We are wiping the HDD and doing a clean install of Yosemite. We'll then restore from time machine. If the problem recurs, we'll do it again but without the time machine restore - in other words re-installing the programs one at a time.

In sleep mode, my iMac screen lights up with a black screen and then off.

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