Why won't my iMac won't "wake up" from sleep mode?

I realize this is an old string, but I'll tell you what I discovered, but first some background. I'm new to the Apple environment. I just got my first ever Mac in the form of an iMac. I also thought I was having this problem, but I discovered if I click the mouse or push the enter key on the keyboard and just wait for almost a minute, it will eventually take me to the login screen. The other thing I discovered is, after one of these events Safari will not load any sites. For this I discovered that turning off and back on Wi-fi Safari works with no problems. I think the Wifi thing is an issue with our particular setup in our house. May not have strong enough signal where my iMac sits. At least, that's what it seems to me. Well that's my 2 cents... hope it helps someone.

Hello cjoplin,

It sounds like your Mac will occassionally not wake from sleep. I would use these troubleshooting steps from the article named:

OS X: When your Mac doesn't sleep or wake

http://support.apple.com/kb/TS5357

Reset SMC

The System Management Controller (SMC) is involved in managing power on your computer. Reset the SMC on your Mac if you are having difficulty sleeping or waking your computer.

Reset NVRAM/PRAM

Nonvolatile RAM (NVRAM)/Parameter RAM (PRAM) stores some power-related settings.Try resetting NVRAM/PRAM if you are having difficulty sleeping or waking your computer.

Test with external devices disconnected

Some external devices can prevent your computer from sleeping. Try disconnecting items other than your Apple keyboard or mouse from the built-in USB, Thunderbolt and Firewire ports on your Mac. If this resolves the issue, try reconnecting your external devices one at a time until you find the device preventing sleep or wake. Check the documentation that came with the device, or contact the device manufacturer for more information.

Try Safe Mode

Check to see if the issue still occurs when the computer is started in Safe Mode. If this resolves the issue, it could be related to a third party software item such as:

• a login item
• a startup item
• a third party kernel extension

Try another user account

Try creating another user account, or log in as guest. See if your computer sleeps and wakes properly from the additional user account. If it does, your issue may be related to one of the following:

• a login item
• an app open in the original user account

You can disable login items from the Accounts pane of System Preferences. Try opening only one app at a time in the original user account to determine which app is preventing sleep. If you isolate the issue to a particular app or login item, check its documentation, or contact the developer of that software for more information.

Thank you for using Apple Support Communities.

All the best,

Sterling

I had these same sort of issues and tried everything. Turns out it is a known issue and Apple has a replacement program for the bad video card in many iMac models. The bad card causes grey screens, black screens, sleep issue, hard drive slowness, system spins, kernel panics, and more! Wow, all fixed at no charge at my local Apple Store!

See:

iMac (27-inch): AMD Radeon 6970M Video Card Replacement Program - Apple Support

Disregard.

Thank you Sterling!

Per your advice, I restarted in SafeMode, put the iMac to sleep and it woke up fine. So, like you said, that indicated to me there was likely a software conflict. So I rebooted normally and looked at my login items and found that there were two items that had the yellow triangle alert next to them (said they were missing) so I deleted them. Then I unmounted my two external hard drives and unplugged them. Then I deleted two pieces of experimental AirPlay software I had been testing (AirParrot and AirServer), then rebooted. On reboot I put the iMac to sleep, waited 30 seconds, hit the space bar and it woke up perfectly. So I set the screensaver to 1 minute, and the "turn display off" setting to 2 minutes and let it run through that routine. I hit the space bar and it woke up perfectly. I have now plugged back in all hard drives and rebooted and done those tests again and it all appears to be fixed!

Thanks again!

UPDATE: I spoke too soon. The problem has returned. I give up. Going to the Apple store.

hi, i also have the same problem that really annoying. i found this issue since i bought a macbook pro 15 early 2011 from my uncle few months ago. he said that the problem started since day one. i upset why didn't he report to the apple store in a first place, he said that the problem didn't bother him. so i started searching for a solution on the internet. i can't even remember how many times I've tried every single solution i found, and I'm sure i I've tried them all, but the problem still persist. but, few days ago i tried logging in with a guest user and put my macbook to sleep for a night and what happened just really surprised me, the mac woke up PERFECTLY, the thing that never happened to me since i bought my uncle's mac. and i wonder what the **** was happening on my main user login and i realised that the guest user doesn't need a password when it wakes from sleep, so i tried to back to my main user login, and disabled the password when log in then put it to sleep overnight, and voila my mac woke up perfectly! tried a few times and the screen freezes when waking up problem never happened since.

did you enable password on your system?

if so, try disabling your password and see what happen.

maybe its not a solution to everyone though, but at least you will know if your mac hardware is doing fine.

thanks

Do you have DuetDisplay or another application that might be messing with display driver stuff?

I had this problem on my macbook, and here's what I did:

I Googled this problem and found out that Things like DuetDisplay may be causing it.

After much Googling and testing, I found the folder that contained DuetDisplay.kext (/Library/Extensions on my macbook pro early 2015 running MacOS Sierra). I just deleted it and restarted my laptop.