I have a PowerMac G5 11,2 Dual 2.3 Ghz with the Overtemp LED red light on the logic board coming on. it isn't on during bootup, or during anything processor intensive, only when the computer is "idle." Heres the thing though, the computer works fine, and the fans are spinning at normal speed. The fans go faster as soon as I do something processor intensive, as its supposed to. Here is another kicker that I can't solve, the light goes off as soon as it is doing something. So if I do something like say encode an entire DVD, the light is off, and the computer looks normal. It isn't the air deflector, as I've done that test and troubleshooting already. I have been reading through Apple's service documents, and they said I may need to run the Thermal Calibration Tool, a tool that looks like is only available to Apple Service Techs (of course there must be other ways to obtain access to this tool, but i will not discuss it here simply because it may be against the rules.) It is also something that looks like I shouldn't be touching because if used incorrectly, it looks like it could just destroy my entire computer! HELP ME! The computer works fine, and has been working fine, despite this annoying red light. I just want the red light turned off so I know that everything is AOK, and fine. Any solutions? I've Googled and Googled, and it looks like the only people who have problems are when the entire computer doesn't turn on, but mine does turn on and works great. They also said it could be water pump problems, but my Mac is air cooled (thankfully) and not liquid cooled. Also, I would like to add, other than the light, I have not had any of the other symptoms that others with the light on have been having. The computer doesn't randomly go to sleep, nor does it ramp fans up and down sporadically. The computer just works, I just want the light off unless something really is broken. I am not having any thermal runaways, and temps are completely normal. I've tried SMU reset, as well as PRAM reset.