Why won't my iMac display sleep?

Question

Level 1

63 points

Why won't my iMac display sleep?

Odd. I updated no software or hardware and changed no preferences, yet beginning yesterday my iMac refuses to allow the display to sleep. Current Energy Saver settings are:

Computer sleep: Never

Display sleep: ~5 minutes

Put the hard disk(s) to sleep when possible: Enabled

Automatically reduce brightness before display goes to sleep: Enabled

The display does not dim nor go to sleep after any period of time. Any suggestions?

iMac (20-inch Early 2008), Mac OS X (10.7.2)

Posted on Jan 17, 2012 9:17 PM

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Answer 1

Iynque

Level 4

1,151 points

Jan 17, 2012 9:22 PM in response to Don Morris

Try resetting the parameter RAM by shutting down and holding command+option+P+R during startup. Hold these keys until you hear the startup chime again, then release and startup normally.

You may have to re-specify settings like power and mouse sensitivity, but it will often fix this issue.

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Answer 2

Don Morris Author

Level 1

63 points

Jan 18, 2012 10:32 AM in response to Iynque

I said ten point seven, not seven -- um, yeah, that worked. Been so long since I had to do that that I forgot it existed. Thanks!

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Answer 3

BulaRae

Level 1

24 points

Mar 6, 2013 7:17 PM in response to Don Morris

I have this same problem just in the past week or two and the first things I did was zap the PRAM and it seemed to solve it for a day or two. What else could it be? We need to get to the source of the problem.

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Answer 4

Don Morris Author

Level 1

63 points

Mar 6, 2013 7:35 PM in response to BulaRae

A running process may be preventing the display from sleeping. As I recall, that was the real culprit with the issue I had above. Check out this article for troubleshooting tips.

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Answer 5

Sep 26, 2013 8:49 PM in response to Don Morris

I was having the same problem after the power went off one evening. I followed Iynque's advice and "shutting down and holding command+option+P+R during startup" fixed the problem. Thanks.

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