MBP (Lion) doesn't go to sleep by itself

[hafr]

My MBP has always gone to sleep automatically as it should, but it started acting up a few weeks ago. From having to wake it up from sleep every morning and several times a day, it now only goes to sleep a handful of times per week - if that. The same thing happened a few months ago, but then it "fixed itself" after a week, no idea why but I reckoned it was some kind of app that had gone crazy.

No app should be the culprit, since the problem persists even if I terminate all of the apps running. I've always had the system defaults in energy saving settings, so the sliders there are not set to "never". I've checked with the console and fixed all the little things that were popping up (now the only thing showing after a night of idle is the Time Machine backups once an hour). I've tried the sharing settings-tip that some people are talking about. As far as I can tell, the HDD isn't being accessed. No new hardware, no new apps...

In short, I've tried just about everything I can think of and everything I can find by searching Google and the forum. But I'm sure I've missed something, so please throw all and any tips, tricks and solutions you know or have heard of my way and I'll even retry those I think I've done to see if this can be fixed.

 

[Garrett998]

I am having the same issue with my MBP running Lion.

No matter how long I leave my computer, it refuses to go to sleep (despite my energy saving settings remaining the default). I can, however, force it to sleep from the menu bar.

Also, when I shut my computer, it still makes a low humming noise (and the fans are running). This is normal for a couple of seconds, but the sound will disappear for a few seconds and come back–it won't go away. When I open my laptop while the sound is being made, my screen is already on but the turns black (the keyboard remains lit up) and to fix this issue I have to adjust my brightness (click the mouse/keyboard won't light up the screen).

So basically something strange is going on with my sleep function (note I am using a 15" late 2011 MBP).