This article explains why PowerBook and iBook computers sometimes do not go to sleep, regardless of the sleep time settings in the PowerBook control panel or Energy Saver control panel.

The following activities may prevent a PowerBook or iBook computer from sleeping unless a low-power condition occurs:

• The PowerBook or Energy Saver control panel Sleep slider selections are set to "Never."
• The serial driver is open and active.
• File sharing is turned on.
• AppleTalk is active (even if the computer is not logged on to a file server, and even if the computer is not connected to an AppleTalk network). Check the AppleTalk control panel or the Chooser to determine whether AppleTalk is active on your computer.
• An internal modem's auto-answer function is on.
• Some third-party applications keep the computer busy, not allowing idle processor time for sleep to occur.
• If you have any System 7.5 Apple Guide help file windows open.
• The CSW 4000 Series Background extension. Use the Extensions Manager control panel to turn off the CSW 4000 Series Background extension. This disables background printing but allows the PowerBook or iBook to sleep normally.
• Version 1.0.3 or earlier of the PowerBook control panel. In this case, the computer does not sleep automatically after the "System Sleeps" time interval has elapsed. (You can still put the computer to sleep by selecting Sleep from the Special menu or closing the computer's cover.)

There is a known issue with the password security feature on the PowerBook 5300 and 190 series computers. If you open the Password Security control panel and password security is turned on and it is set to "ask for password on wake", the PowerBook does not sleep. One workaround is to turn off the "ask for password on wake" feature. If this is done, the PowerBook can be put to sleep. This issue can be resolved by installing the System 7.5 Update 2.0 (or later system software), which includes the Password Security 1.0.3 control panel.

Check to make sure that there are no extensions or control panels in the System Folder that may be causing the computer to assume that the system is busy. (For example, the FocalPoint II INIT has been shown to cause this; others may also.)

Make sure there are no applications currently running that would keep the system busy. (For example, Microsoft Word's automatic repagination option keeps the system awake.)

An extension called Insomnia came on the Install Me First disk with some versions of the system software. If this extension is mistakenly put into the Extensions folder in the active System folder on the hard disk, the PowerBook does not go to sleep. It should be removed from the hard disk. Insomnia is an extension that keeps the PowerBook from going to sleep during the installation process when starting from the Install Me First disk.