Ashwin Lewis
If your iMac goes to sleep and won't wake up, there are several potential solutions. Firstly, check if your iMac is charged, as a drained battery might give the illusion that it won't wake up. You can also try adjusting your sleep settings, disconnecting external peripherals, or resetting the SMC (System Management Controller) and NVRAM (non-volatile random-access memory). If these solutions don't work, you may need to recover your data and reinstall macOS, or contact Apple Support for further assistance.
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What You'll Learn
Check for software or hardware issues
If your iMac won't wake up from sleep, there could be several software or hardware issues at play. Here are some detailed steps to help you troubleshoot and resolve the issue:
Software Issues
- Bluetooth Settings: Check your Bluetooth settings. Using a mouse or keyboard via Bluetooth can sometimes wake up your iMac. To prevent this, go to "System Preferences/System Settings", choose "Bluetooth", click "Advanced", and uncheck the option "Allow Bluetooth devices to wake this computer".
- Sharing Settings: Using shared services or resources on your iMac, such as a shared printer or accessing shared files, can interfere with sleep mode. To fix this, go to "System Settings", click "General", then "Sharing", and turn off any services you don't need.
- Network Access Settings: If you use a shared network, another user might be waking your iMac remotely. To prevent this, change your Network Access Settings by going to "System Settings", clicking "Energy", and turning off "Wake for Network Access".
- Sleep Settings: Ensure that your sleep settings are correctly configured. Check the "System Information" app/Power tab to view your sleep and power settings. Make sure the number after "Hibernate mode" is set to 0, as higher numbers indicate a deeper hibernation mode that may require a full power reset.
- Activity Monitor: Background processes can prevent your iMac from sleeping or waking up. Open the Activity Monitor ("Applications > Utilities > Activity Monitor") and click the "CPU" button to check for any unexpected CPU usage.
- Apps and Spotlight Indexing: Certain apps, such as Music or DVD Player, can keep your iMac from sleeping by accessing disks or the optical drive. Additionally, if Spotlight is indexing your hard disk, your iMac won't go to sleep. Open Spotlight to see if it's indexing, which can take several hours depending on the number of files.
- External Peripherals: Disconnect any external peripherals, such as USB or Thunderbolt devices, as they can sometimes cause issues with sleep mode. Disconnect them one by one to identify the problematic device, and then replace it if necessary.
- Software and Malware: Unwanted software or malware running in the background can interfere with your iMac's normal operations, causing wake-up problems. Use an antivirus tool, such as MacKeeper's Antivirus, to scan and remove any potential threats.
Hardware Issues
- SMC (System Management Controller): Errors in the SMC, which manages low-level settings like sleep and wake, can cause your iMac not to wake up. Perform an SMC reset by shutting down your iMac, then pressing Control + Option + left-side Shift (or right-side Shift for T2-based Macs) for 10 seconds. Release the keys and power on your iMac.
- NVRAM (Non-Volatile Random-Access Memory): Resetting NVRAM can be a fix. Shut down your iMac, then press the power button along with Option + Command + P + R for 20 seconds. Release the keys when you hear the startup chime twice (or when the Apple logo shows up and off twice for T2-powered Macs).
- Battery: If your iMac has been in sleep mode for extended periods, its battery may be drained, giving the impression that it won't wake up. Plug in your iMac and charge it for about half an hour, then try pressing the power button.
- Memory Modules: Using incompatible memory modules can cause issues with sleep and wake functions. Ensure that you are using compatible RAM with your iMac.
If none of these software or hardware fixes resolve the issue, you may need to recover your data and reinstall macOS, or seek further assistance from the Apple support team.
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Reset the SMC (System Management Controller)
Resetting the SMC (System Management Controller) can resolve some iMac issues, such as sleep problems, fan noise, and not starting up. The SMC is a subsystem on Mac that manages low-level settings of sleep and wake, hibernation, battery supply, etc. Therefore, errors in the SMC can result in your iMac refusing to wake up from sleep.
Before resetting the SMC, try each of the following steps in order and test the issue after each step to see if the issue still occurs:
- Press and hold the power button until your iMac shuts down. You will lose unsaved work in any open applications.
- Press the power button again to turn on your iMac.
- Press Command-Option-Escape to force quit any application that is not responding.
- Put your iMac to sleep by choosing the Apple () menu and selecting Sleep.
If the issue still isn't resolved, you can reset the SMC using the following steps:
- Shut down your iMac by choosing the Apple menu and selecting Shut Down.
- Press and hold the Control, Option, and left-side Shift keys on your keyboard for 10 seconds. If you use a T2-based Mac, use the right-side Shift key instead.
- Release the keys and wait a moment.
- Press the power button to turn on your iMac.
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Update your Mac
If your iMac won't wake up from sleep, there are several things you can try. Firstly, check if your iMac is simply out of battery by charging it for half an hour and then trying to turn it on. If that doesn't work, you can try resetting the SMC (System Management Controller), which manages the low-level settings of sleep and wake, among other things. To reset the SMC, shut down your iMac by holding down the power button, then press Control-Option-left-side Shift for ten seconds. If you have a T2-based Mac, use the right-side Shift key instead. Release the keys and wait a moment, then try to turn your iMac on again.
If your iMac still won't wake up, you should check your sleep settings. Go to System Preferences/System Settings and select "Bluetooth". Click "Advanced" and uncheck the option "Allow Bluetooth devices to wake this computer". If you're using a shared network, another user might be waking your iMac remotely, so you may need to change your Network access settings. Go to the Apple menu and select "System Preferences", then click "Energy Saver" and turn off "Wake for network access".
Another solution is to reset the NVRAM (non-volatile random-access memory), which is used to store certain system-related settings. To do this, shut down your iMac by pressing the power button, then press the power button along with Option + Command + P + R for 20 seconds. Release the keys when you hear the startup chime go off twice. If your iMac still won't wake up, you may need to recover your data and reinstall macOS.
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Check sleep settings
If your iMac goes to sleep and won't wake up, you may need to change your sleep settings. To do this, you can check the following:
- Check that the sleep mode is enabled.
- Change the amount of time that should pass before your iMac goes to sleep. To do this, click the pop-up menu next to "Turn display off on battery when inactive" and choose an option. You can also do this for when your iMac is plugged in by clicking the pop-up menu next to "Turn display off on power adapter when inactive".
- If you don't want other users to wake your iMac remotely to use its shared resources, go to the Apple menu and turn off "Wake for network access".
- If you are using a mouse or keyboard via Bluetooth to wake up your iMac, you can change this setting. Go to "System Preferences/System Settings", choose "Bluetooth", click "Advanced", and uncheck the option "Allow Bluetooth devices to wake this computer".
- If you are using a shared network, another user might be waking your iMac remotely. To change this, go to your Network access settings.
- If you are using shared services on your iMac, this can interfere with the sleep mode. For example, using a printer connected to your iMac or accessing shared files stored on it can wake up your device. To change this, go to System Settings, click General in the sidebar, then click Sharing, and turn off the service you don't need to use.
- If you have peripherals connected to your iMac, these can sometimes cause issues. Try disconnecting them one by one to see if this is the problem, then replace any damaged peripheral.
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Disconnect peripherals
If your iMac won't wake up from sleep, it could be due to issues with peripherals connected to it. Peripherals include any external devices such as a mouse, keyboard, or printer.
To identify if a peripheral is causing the issue, disconnect them one by one and attempt to wake your iMac after each disconnection. This will allow you to ascertain which peripheral is causing the problem. Once you have identified the problematic peripheral, you can try replacing it with a new one.
Additionally, you should check if your peripherals are connected via Bluetooth. To do this, go to the Apple logo, select "System Preferences/System Settings", choose "Bluetooth", and click "Advanced". Here, you should uncheck the option "Allow Bluetooth devices to wake this computer".
If disconnecting peripherals does not solve the issue, you may need to try other troubleshooting methods. These include checking your sleep settings, performing an SMC reset, or reinstalling macOS.
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Frequently asked questions
There could be several reasons why your iMac won't wake up from sleep mode. First, check if your iMac is charged. If it is, then try pressing the power button to wake it up. If that doesn't work, try resetting the SMC (System Management Controller) by holding down the power button for a few seconds to force a shutdown, then pressing Control + Option + left-side Shift key for 10 seconds.
If the above steps don't work, you can try resetting the NVRAM (non-volatile random-access memory). To do this, force a shutdown by pressing the power button for a few seconds, then press the power button along with Option + Command + P + R keys for 20 seconds. Release the keys when you hear the startup chime twice.
Yes, you can try disconnecting any external peripherals, as issues with connected devices can sometimes cause problems with sleep mode. Disconnect devices one by one to identify which one may be causing the issue. Additionally, check your sleep settings to ensure sleep mode is enabled, and that no other users are waking your Mac remotely.
