Cold Weather Operations Force PowerBook PMU Reset

Batteries don’t work well in the cold, and with the -20°F nights we’ve had, I think I can say it’s been cold here lately. I woke my PowerBook from sleep in sub-freezing temperatures this morning and got a few minutes of work out of it before it put itself to sleep again. I popped it into my computer bag and ran off to work, where I was troubled to find it refusing to wake from sleep — even when plugged into the AC adapter in a warm room.

A PowerBook’s power manager (the PMU) will refuse to wake the computer when the battery is very low. The thinking is that to wake from sleep in such a state would likely result in complete power loss and a resulting loss of RAM contents.

Clearly, the extreme cold had confused the PMU and it needed to be reset. Many PowerBooks and iBooks have a PMU reset button tucked away among the ports on the back or side, but the aluminum G4s don’t. These ‘Books require an awkward keybord combo to do the job. Apple’s instructions, directly from the knowledgebase article are as such:

  1. If the computer is on, turn it off.
  2. Reset the power manager by simultaneously pressing and then releasing Shift-Control-Option-Power on the keyboard. Do not press the fn (Function) key while using this combination of keystrokes.
  3. Wait 5 seconds.
  4. Press the Power button to restart the computer.

The article has instructions for the following PowerBooks and iBooks:

And a another article has similar instructions for really old school, pre-G3 PowerBooks.