I just bought a refurbished G5 and have been using it for a few days with no problems. It is an early 2005 dual 2.3ghz. Anyways, yesterday, I left it on for a few hours while I was gone to download something, and when I came back, the fans were at full speed. Thinking it had a memory leak or something that was causing it to max out the cpus, I felt the air coming out, and it was cold. I then remembered seeing a lot of talk about fan troubles with the g5. I have tried to reset the pram, nvram, pmu, and reset-all in open firmware. I have also pulled the motherboard battery, which is the only thing that did anything to the fans. Other than after pulling the battery, the fans start at full speed from when I press the power button. After the battery being pulled, it takes like 5 seconds after i press power, almost in unison with the boot sound, for the fans to turn on and ramp up to full speed. I have been trying to find a solution to this since it started yesterday with no luck. I also downloaded istat (i believe that's what its called) and a few widgets that monitor temps and fans, but none of them seem to be able to read the fan speeds. The temps are low (120 for cpus, 80 ambient, 130 memory heatsink), so it's not overheating, but the fans are stuck at full. Is the last step trying to contact apple and see if they can run a diagnostic to identify the problem, or is there any other way to try to fix it?