My Mac will not sleep

Are you on a network? Try going to System Preferences > Energy Saver and uncheck "Wake for Network Access."

This is for a Mac that won't sleep.

Here is Apple's KB article HT1776 with their tips.

Mine follow;

USB devices and hubs often cause Macs to not sleep or wake quickly from sleep (notably HP printers and scanners, HP all in ones, and Cannon scanners). Disconnect all USB except for keyboard and mouse and try. If it sleeps, add one back at a time testing after each one to find the culprit.

If you've set your Mac to receive faxes, it may not be able to sleep. It might also have a damaged preferences file.
If you use your Mac for faxing, open System Preferences. click Print & Fax, click the Faxing tab, and uncheck the Receive Faxes On This Computer box.

If that doesn't work or you've never faxed on your Mac, go to Finder/Hard Drive /Library/Preferences/SystemConfiguration and delete the com.apple.PowerManagement.plist and com..apple.AutoWake.plist files (if your Mac asks, type your admin. password).
If the latter file isn't present in the folder, go to user name(probably your name)/Library/Preferences, delete the com.apple.systemuiserver.plist file, and reboot your Mac.

Hope this helps!

P.S. One member here reported this ( Michael Gleason);
"I have had this problem with my IMac G5. It is surprisingly irritating. LaCie's Silverkeeper backup software was the cause. By default it gave itself permission to wake up the computer to check if a backup was needed. Do you have this or a similar program installed which has scheduled activities including wake-up permissions as an option?"

Dave Hamilton provided this link, xlr8yourmac.com, to a member, which addresses failure of deep sleep with some users that updated and added new FireWire and USB card.

Also, here is Apple KB article TA2469 about PCI cards and sleep.

tomhorvat adds this; After few days of messing around I found out that I had desktop background (wallpaper) set to change every 1 minute.
After unchecking "Change picture..." in system preferences (under Desktop/Screen saver), my powerbook went to sleep all by itself.

Tristan Currier noticed this; "I have a Canon printer(shared) and my imac would not sleep. I opened up printer/fax in system prefs and noticed it said the printer was in use when it was off. Opened up the printer queue and noticed about 7 pending documents. Deleted them all and now it sleeps.
Check the printer queue!"

Allan Jones says "sometimes there is Network activity: launch System Preferences > Energy Saver > "Options" tab and uncheck "Wake for Ethernet network administrator access."

One user has had success, after trying all these tips, using an App. called PleaseSleep. I've never used it though.

Good Luck!  DALE

If all else fails (as it has with me) there is a little app called Lights Out

This never fails. The disadvantage is that it will put the computer to sleep after the specified interval, even if it is in the middle of doing something. However it can be configured by application so that if for example you want to leave Photoshop batch processing 10000 files it will do so without sleeping.

Also gas hot corner option to prevent auto sleep if required.

My mac mini has suddenly refused to auto-sleep after a preset amount of time. It's always worked in the past but not as of a few days ago. No hardware/software changes have been made. I've tried all the tips your mentioned above, including resetting SMC/PRAM, and unplugging all external cables.

I've even booted into Safe Mode and it still won't auto sleep. It DOES sleep just fine if I hit the power button or select Sleep from the Apple menu. But refuses to sleep after a preset amount of time.

I've also tried Repair Permissions in Disk Utility. I am going to end up wiping and reinstalling OSX but figured I'd post here first.

Thanks so much for any help you can give.

Look at the kernel log in console. Type 'wake reason' in the text search. It should tell you what system is waking it.

Looking in the console I see nothing when I search for "wake reason" or "wake". I see no mention of the computer even trying to sleep, unfortunately.

Message was edited by: zarathustrian

Is the Energy prefs set to not allow sleep? If it is not even trying to sleep, you won't see a wake message.

When you looked in the console, did you look at the kernel.log, or just All Messages or Console Messages?

My energy pref is set to allow sleep, yes. I have always had it set to 15 minutes before sleep, but since it stopped working, I've tried changing it to 1 minute, and 5 minutes, etc.

How do I specifically look at kernal.log? I had it set to All Messages.

Scroll down the list and look under private/var/log.

I had the same problem, and eventually discovered it was the USB memory stick I had been leaving plugged in. As soon as I ejected and removed it, problem solved.