Can anyone confirm this?
What are the character istics of a normal fan? how often does it run? is it variable etc .
Under normal operation, the fans are nearly silent. You usually can't hear them over the hard drive's spinning sounds.
My PowerBook G4 17-inch 1ghz (10.4.11) does not speed up the fans until the temps (per Temperature Monitor: http://bresink.com/osx/TemperatureMonitor.html ) reach about 140F/60C. They then ramp up and run faster until the temps fall to about 130F/54C, then revert to being silent. And about the only time the computer gets to 140F is if I'm playing a complex 3D graphics game (example: Unreal Tournament 2004 demo).
It's the same with later notebooks. My 2007 MacBook Pro will read fans and the default idle speed-2000 rpm--produces little or no sound. The fans have to get up to about 2400 rpm for me to start noticing them.
Unless you are getting sudden shutdowns that indicate overheating, I'd put the issue in the "No Problem Box." You can do a lot to help the PB run cool. First, don't use the computer on your lap or on a padded surface without a lapboard. The underside of the case acts as a heat sink and air must be able to move under the case.
Also, the hinge area on the back of the case is an exhaust port that needs to be unimpeded.
Regarding AHT, the only downloadable version doesn't work right. Apple put out a corrected version that they would mail you on CD, but I don't know if that offer is still on the table as the computers are now well beyond Apples' support cutoff.