G5 booting issue

My g5 Has the Same Problem! When this problem with The hyperventilating Fans occurs I just Power the g5 down and wiggle the ram sticks a little bit .... that does the trick I think it's some kind of connector or ram problem

Also Check your hibernation settings

G5's cannot hibernate/safe-sleep. They can sleep, but not hibernate as laptops and G4 PowerMacs can be modified to do.

There was an issue with the G5s oh so long ago that if you let them sleep they would not wake up and you were forced to shut them off and turn them back on. Apple "fixed" this with a firmware update, but I've since then always set the G5 I use to never sleep. I let it turn the monitor off, but not sleep.

I know this is not entirely related to the issue here, but maybe setting the Mac to not sleep might help.

Of course that G5 was on 24/7 (including weekends and holidays) and my boss was paying the power bill each month…

This is again, likely a sensor issue.

See my posts in this thread.

I've had my share of these problems with G5 units.

Flowchart for G5 Fan Speed Concerns:

Zap PRAM;
Check airflow door light sensor;
Dust system with compressed air (can, or compressor);
Reset PMU;
Run Apple Calibration test;
Update Firmware;
Check HDD position; some systems default to one bay or the other;
Check primary components (RAM, HDD/SMART Status).