iMac won't go into sleep mode in Yosemite

I've been having the same problem: The energy saver functions that put the screen and then the HD to sleep shut down the screen, but not the HD no matter how I set them. I CAN put the HD to sleep with the file menu command or the computer's power button. I have just about all the things mentioned in this thread with no luck. What I did eventually discover was that if I signed out of iCloud, the HD was finally allowed to sleep. Evidently there is something that iCloud does that interferes with the energy saver sleep command. Looking in Terminal I see "Sleep prevented by UserEventAgent". Looking further, there is a "background task" called "co.apple.bird.sync". "Bird" (which sometimes shows up in Activity monitor, sometimes not) has something to do with synchronizing iCloud. This is what lead me to try signing out, and it worked.

Unfortunately, this is not a good long-term solution, because I want my iPhone and my iMac to communicate. Does anyone have any idea how to prevent iCloud from interfering with the Energy Saver sleep function?

I've been fretting over this for weeks and have just fixed the problem! I realised the problem started happening around the time I had downloaded a new application. This application had set itself to open on startup, which was getting on my nerves anyway because I hardly ever use it. So I went to "users and groups" in "system preferences" and deleted it, amongst others, from the list. And now my imac is sleeping soundly.

Same here. iMac, mid-2011, freshly installed Yosemite. Display will go into Sleep, but hard drive won't spin down. Or does so erratically.

I had this problem as well. I fixed it by simply running verify/repair disc permissions, then restarting. My iMac will now sleep (via short cut key - option/command/eject, or pressing power button, or selecting from menubar/Apple/sleep) - and it will now stay asleep.

I'm having the same issue.
I tryed to do this, and it didn't work for me. It went to sleep after 2 minutes, and then started again right after.
Any other suggestions?

Hi, I've the same problem since Yosemite. I noticed a lot of CPU activity caused by Chrome so I shut down Chrome and the screen went to sleep. I need to keep an eye on this one before I can be certain that Chrome is the problem.

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Well, ten minutes later. No special CPU activity with Chrome and now the screen goes to sleep. Chrome must have been doing something at the time to stop the system from powering down. This could be a problem when one leaves the desk and expects that the Mac will be protected. Very bad if one is on battery power and finds that there is no power left.

Chrome is not the problem for me. And I don't even have a lot of CPU activity.

My screen shuts down... But I can hear the harddrive running. It shut's down after a couple of minutes. But then it starts up again a second after.

Hi there,

I have a Mac mini running Yosemite and sleep does not work either. The monitor shuts off but the mini stays on. The indicator light on the front stays at its fixed setting, instead of slowly pulsing, when sleeping. Interestingly, if i click sleep from the Apple menu, sleep works.

I'm Having the same issue. All power setting are correct but will not automatically enter sleep mode.

All,

Same situation here. iMac 13,1 goes to sleep, and wakes up immediately. If I select Sleep from menu, my display goes blank immediately, then after a couple of minutes the unit goes to sleep (I can /feelhear the hard drive still spinning until it does), then wakes back up almost immediately, sometimes activating the display sometimes not, but I can tell the unit is still "powered" on and not full alseep.

Robert

Sleep - Why your Mac might not sleep or stay in sleep mode

Sleep - Won’t

Yeah Eric... I think most of us knows this.

But the problem for us started after we upgraded to Yosemite. It worked perfectly before.

Pretty much know this by heart. I can shutdown all services/apps, etc, and the system still will not sleep. Went to sleep fine in 10.9.5 and have not changed anything or any settings except for the upgrade to Yosemite and iCloud Drive.

Robert

Don't know if it's relevant here, but my iMac is sleeping fine using the power button PROVIDING ... it's not in the middle of a Time Machine backup. It also wakes periodically to do system automated things, but left alone will sleep again on it's own.

Send Apple feedback. They won't answer, but at least will know there is a problem. If enough people send feedback, it may get the problem solved sooner.

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