Hello Apple Friends and Users:
I was trying to fix a problem related to sleep mode and tried to use Activity Monitor to identify which apps may cause problems. For some reason the column "Preventing Sleep" is gone in Activity Monitor (OS X 10.10.5 on an Early 2008 24" iMac). I cannot find it anymore. I am also missing the "Avg Energy Impact" column, but not as much.
Does anybody have an idea what is happening?
Thanks,
Hal.
At the risk of an obvious question, you are looking at the Energy section of Activity Monitor, correct? "Average Energy Impact" is there, unless the columns have been re-selected — control-click on the column header to re-select the headers you want viewable. There's an "App Nap" column there which might be interesting to you, and the column that shows as "Preventing Sleep" is hidden in the column browser as "Power Assertion".
Thank you MrHoffman. I tried this, but the options to select "Average Energy Impact", "Power Assertion" or "Preventing Sleep" are simply not there. "App Nap" shows in the list as well as "Energy Impact" and several others. There is no difference in the columns offered whether I control-click the column header or go via menu View | Columns.
Okay. I'd then try a different and newly-minted and temporary user login on your Mac and see if that demonstrates similar misbehaviour. If it does not, then that implies something odd lurking in your local preferences; something in your login. If it does show similar misbehaviour, then I'd see if a reboot clears this, and would then try the usual recovery-partition disk repair, reinstall the 10.10.5 combo update, then reinstall OS X.
My tests were with OS X 10.10.5, for completeness.
You are right, there is a different behavior for the users in my machine! Interestingly enough, the column "Preventing Sleep" shows on the Energy tab for another user, but the option is not listed in the control-click selection. Very odd.
Do you know, which plist file I need to delete?
Shut down Activity Monitor everywhere, and have a look around for ~/Library/Preferences/com.apple.ActivityMonitor.plist
Perfect. Deleting the preference file did the job! Thanks!!
Hi, I have the same problem as OP, only my Activity Monitor is still not showing Preventing Sleep as a column to select. I am on a MacBook Pro, Version 10.9.4. I do not have the columns available to select on a Guest account, either.
I am attaching a screenshot so you can see what my options are. Do you have any suggestions on how to see if an application is preventing sleep? Thank you.
From what I can tell of it, you're running a version of OS X that's too old for that column. 10.9.5 is "current" in that release series, but that release doesn't have that "Power Assertion" column available. If you need this and if your Mac supports it and if your other software permits it, back up your disk once or twice to external storage (so that you have a recovery path, if something fails), and then upgrade OS X. OS X 10.11 is current.
Some columns missing in Activity Monitor
