Mavericks screen lock occurs immediately instead of after 15 minutes of sleep I'm on OSX 10.9 on a late 2013 Macbook Air. iCloud Keychain is disabled, FileVault is turned off, and my Energy Saver settings are all at their defaults. I want to require a password after 15 minutes of sleep or inactivity, which should be straightforward. However, I am getting some strange behavior. 

A- With the Require Password &lt;option&gt; hours after sleep or screen saver begins option in the "Security and Privacy" preference pane unchecked, my machine does not ask for a password if I close and immediately open the lid.

B- With the "Require Password &lt;option&gt; hours after sleep or screen saver begins" option in the "Security and Privacy" preference pane checked and the timeout set to 15 minutes, my machine requires a password if I close and immediately open the lid.

I want to be able to wake from sleep without a password if it has been less than 15 minutes since I last used my mac. This should be simple, but for some reason the appropriate setting isn't having the desired effect. Any ideas on how to fix this so the setting works as it should?
I have tried to replicate and analyze your problem.

The key word here is close the lid and "immediately" open it again.

There is a file called com.apple.screensaver.plist located in your user library preferences folder that should change when you change the settings for password timer. 

While observing it there is actually a slight delay in writing that file, since a temporary version is written first. If you do the immediate stuff it is possible the .plist file is not correctly completed so your 15 min delay is not working.

In your case I would take a wild ques that plist file does not change the settings to 15 minutes and it is stuck to the "Immediately" request password.

That can also be caused the corrupt ACL permissions, or the immediately action you are doing.

Make sure the plist file has the accurate date/Time stamp before attempting to close the lid.

To test log in as another user and try again. If it works with other user reset your ACL.