My Mac is possessed.

[panache45]

I have a G5 Mac. This morning I awoke to find it sounding like a vacuum cleaner, with a bright red light emanating through the mesh, near the bottom. The keyboard was dead, and the power button didn’t do anything, so I pulled the plug, then plugged it back in and restarted. There’s been no problem since.

What the hell was that about? That red light was scary.

[Sunspace]

Paging MacTech! Paging MacTech!

Maybe the power supply malfunctioned and was heating up? The ‘sounds like a vacuum cleaner’ seems to indicate the the fans were running at top speed. Is the machine clean inside (no giant dust deposits, etc)? Something might have shorted.

Or the motherboard was hosting a portal to hell.

[control-z]

Be sure you’ve backed up any important files.

[beowulff]

This is a common problem with G5 towers. It’s usually caused by the Kernel crashing before the machine goes to sleep, resulting in the fans going into full-speed failsafe mode. I have this happen every few months. It’s mostly an annoyance.

[seal_cleaner]

Open in single user mode, do an fsck. Also get a copy on Onyx (free).

[rbroome]

@panache45

I have a G5 Mac. This morning I awoke to find it sounding like a vacuum cleaner, with a bright red light emanating through the mesh, near the bottom. The keyboard was dead, and the power button didn’t do anything, so I pulled the plug, then plugged it back in and restarted. There’s been no problem since.

What the hell was that about? That red light was scary.

sounds like you were lucky to wake up that morning!
The Mac Ogre must not have been hungry…

Seriously,
There is an LED on the motherboard that lights up when there is a power supply problem (depending on the model there are 2 or 3 LEDs that mean different things). I haven’t seen a red light before, mine have been green, but possession is a funny thing.

Apparently unplugging your machine successfully reset the power supply.

[beowulff]

@beowulff

This is a common problem with G5 towers. It’s usually caused by the Kernel crashing before the machine goes to sleep, resulting in the fans going into full-speed failsafe mode. I have this happen every few months. It’s mostly an annoyance.

Happened to me again this morning.
So, now I have to do all the VooDoo which fixes the problem for another few months:

1. Reset the SMC by pressing the reset switch on the motherboard near the battery.
2. Zap PRAM (hold CMD-OPT-P-R down while booting).
3. Reset the Sleep manager by setting to defaults in the Energy Saver control panel.

Note that the suggestions to run fsck on your drive will not affect this issue. It’s also not a power supply problem.

[Cartooniverse]

Zap PRAM. This sounds familiar. When my older MacBook Pro was acting flaky, a friend suggested I do this. Seemed to help.

What is the PRAM and why does it need zapping? Sorry for the hijack, it does seem related to OP.

[beowulff]

@Cartooniverse

Zap PRAM. This sounds familiar. When my older MacBook Pro was acting flaky, a friend suggested I do this. Seemed to help.

What is the PRAM and why does it need zapping? Sorry for the hijack, it does seem related to OP.

PRAM (Parameter Random Access Memory) is a small non-volatile bit of memory where lots of system settings are stored, including the current boot disk, speaker volume, and apparently, some power management settings - which is why “Zapping” (reseting it to defaults) seems to help.