Disclaimer: Apple does not necessarily endorse any suggestions, solutions, or third-party software products that may be mentioned in the topic below. Apple encourages you to first seek a solution at Apple Support. The following links are provided as is, with no guarantee of the effectiveness or reliability of the information. Apple does not guarantee that these links will be maintained or functional at any given time. Use the information below at your own discretion.
The fans in the PowerMac G5 are software controlled.
This means that the MacOS X kernel reads the temperature sensors located inside the PowerMac's case and periodically updates the fan controllers with information regarding how fast the fans should be turning.
However, if something goes wrong and the operating system cannot relay this information, say because the kernel panicked or a system hang of some type occurred, this information will not be sent.
When this occurs, the fans will ramp up to their highest speed in order to protect the components on the inside of the case. Since the temperature sensors are not being read, the most prudent measure for the system to take is to provide the maximum cooling it is capable of, to prevent any possible heat damage to system board components or internal storage devices.
The question then becomes a matter of diagnosing exactly why the kernel has stopped communicating with the fan controller. If a system panic message appears on the screen, the cause is obvious, but if the screen simply remains blank, analyzing the situation is much more difficult.
The number one thing to check is what types of devices are attached to your machine. Many third party USB devices, particularly hubs, do not precisely follow proper protocols and can cause problems, particularly when the PowerMac has entered or is awakening from sleep mode.
Another prudent measure is to run the various hardware tests located on the Apple Hardware Test disc that originally shipped with your machine. This may show that a hardware issue has arisen with your machine; this is particularly important if your system is new, as the most likely times for any electronic component to fail are when it is new and at the end of its useful service life.
Finally, if you have made any modifications to your system, such as adding additional memory or installing an additional internal disk drive, you may also want to try removing those in order to see if your problems persist.
Do you want to provide feedback on this User Contributed Tip or contribute your own? If you have achieved Level 2 status, visit the User Tips Library Contributions forum for more information.
Replies