I have 4 Imacs on my home network. 3 of them always restart after a power failure of any time duration but one only restarts if the power is off a maximum 15 seconds. If the failure is longer than that it won't auto reboot. All energy saver control panel settings are identical. Any suggestions? Could it be the internal battery? Thanks for any ideas.

Have you tried zapping the PRAM and resetting the mobo via the CUDA switch (or RESET button, actually)? If they don't help,a new battery would be my next try. It may take longer than 15 seconds for the power to drain from the system after the supply is cut off. Maybe try swapping the battery with one of the other units to see if the problem follows the battery before investing the $10 in a brand new one. The only other possibilities I can think of would be the PAV board or the mobo itself, neither of which are particularly cheap or easy to replace. -Chad

Thanks Chad. Yes, I did try those procedures (if you meant the reset button next to the programmers button on the in/out side panel). I am definately getting the standard low battery symtoms, the "1904" date so I have ordered a new battery from www.mac-batteries.com/ ( $6.44 which includes shipping). I have been unable to find out if the auto restart would even be related to a low/dead battery but it seems like it would make sense. paul

Yes, the lack of auto-restarting is due to the dead battery. The power goes out, the Mac forgets its power settings, and it won't restart. With a good battery, step 2 in that sequence doesn't happen. p

Thanks Pickle- I just checked the battery and the voltage was a big 0. It must have drained itself. That's great news. I had just finished celebrating when suddenly another Imac (400dv) went totally black and won't reboot although all voltages look normal on the boards. CRAPOLA. I'm troubleshooting it now. Any ideas?

Just as an FYI - keeping Macs plugged in keeps their batteries from running down. Replacing the PRAM battery on a Mac that has +5V trickle current on its PSU (all desktop Macs since about the IIcx in 1989) is almost *never* necessary - maybe once in 10 years or so - if you keep the Mac plugged in. First thing I'd check on the recently-dead one is cold solder joints. The fanless iMacs aren't as bad as the Rev. A-C, but the early iMacs have been known to have video board failures due to heat, which causes the solder joints to crack. p

thanks P- The new battery made everything normal once again on Imac #1. That dead battery may have occured due to a PMU crash. From the manual it says "...if the PMU crashes the battery life goes from about 5 years to about 2 days if the PMU is not reset.." I found only 4.75V on the trickle charge and 3.75V on what should be 5V at the J7 connector on the logic board in the dead machine. I eventually took it to my local Mac repair...no word yet. paul