Resetting PowerBook and iBook Power Management Unit (PMU)
Please see the document provided via the link to carry out the reset , as there are many models and differing ways to reset PMU.
PowerBook G4 Computers: How to Identify Different Models , you will need to find out what Mac Power book you have ..
After the reset, on some iBooks and PowerBooks, the system clock is set to 00:00 etc.
This article refers to Apple products manufactured November 1997 or later. For products manufactured before that date, see "PowerBook: Resetting Power Management Unit (PMU)".
About the Power Manager
The Power Manager is an integrated circuit (computer chip) that is usually on the logic board of the PowerBook and iBook. As the name implies, it is responsible for power management of the computer. It controls backlighting, hard disk spin down, sleep and wake, some charging aspects, trackpad control, and some input/output as it relates to the computer sleeping.
Over time, the settings in the Power Manager may become unusable, which can result in operational anomalies with the computer. Examples include not turning on, not waking from sleep, not charging the battery, or not seeing the AC Adapter, among others.
Resetting the PMU is not intended for resolution of a stall or situation in which the computer is unresponsive. A PMU reset should not be necessary except as a last resort in cases where a hardware failure of the power management system is suspected. Performing a PMU reset returns the iBook and PowerBook hardware, including NVRAM, to default settings and forces the computer to shut down.
See below for instructions on locating the reset button or key combination for your model of iBook or PowerBook.
If your computer is earlier than the models listed here, see "PowerBook: Resetting Power Management Unit (PMU)".
Warning: Resetting the Power Manager on any PowerBook or iBook will permanently remove a RAM disk, if present, and all of its contents.
PowerBook and iBook models covered by the reset .
PowerBook G4 (15-inch 1.67/1.5GHz), PowerBook G4 (17-inch 1.67GHz), PowerBook G4 (15-inch Double-Layer SD), and PowerBook G4 (17-inch Double-Layer SD)
PowerBook G4 (12-inch), PowerBook G4 (12-inch DVI), PowerBook G4 (12-inch 1.33GHz), PowerBook G4 (12-inch 1.5GHz), PowerBook G4 (15-inch FW 800), PowerBook G4 (15-inch 1.5/1.33GHz), PowerBook G4 (17-inch), PowerBook G4 (17-inch 1.33GHz), PowerBook G4 (17-inch 1.5GHz)
PowerBook G4 (DVI) and PowerBook G4 (1GHz/867MHz)
PowerBook G4 and PowerBook G4 (Gigabit Ethernet)
iBook (16 VRAM), iBook (14.1 LCD 16 VRAM), iBook (14.1 LCD 32 VRAM), iBook (32 VRAM), and iBook (Opaque 16 VRAM), iBook (Early 2003), iBook (800 MHz 32 VRAM), iBook (900 MHz 32 VRAM), iBook (14.1 LCD 900 MHz 32 VRAM), iBook G4, iBook G4 (Early 2004), iBook G4 (Late 2004), iBook G4 (Mid 2005)
iBook (Dual USB), iBook (Late 2001), and iBook (14.1 LCD)
iBook and iBook (FireWire) computers
PowerBook G3 Series (Bronze Keyboard) (M5343)
PowerBook G3 Series (M4753)
PowerBook G3 (M3553)
Please see the document provided via the link to carry out the reset if your mac is not listed above , as there are many models and differing ways to reset PMU.
If there is still no change in the issue after testing , please try reseting the Pram:-
Resetting the Power Manager and PRAM
Resetting the parameter RAM (PRAM) when the computer is shut down also resets the Power Manager.
The following process resets both the Power Manager and the parameter RAM.
If the computer is on, turn it off.
Make sure the Caps Lock key is not down.
Restart the computer. Immediately after hearing the startup sound,
simultaneously press and hold Command-Option-P-R.
(If you do not hold down the key combination within 5 to 10 seconds after the computer restarts, you must repeat steps 1-3.)
Hold down the keys until you hear the startup sound again. Then release the keys.
If the computer shuts itself off, press the reset button on the back of the computer to turn it back on.
When the computer has finished starting up, restore any custom settings for the desktop pattern, memory, network, AppleTalk, trackpad, power conservation, and so forth.
Does this help?