Strange fan issue


Artifical Lifeform
I have an iMac G5 1.8 GHz all right. Sometimes something really strange happens.

When I reboot, I hear the chime (this Apple Bong sound) and then the fan starts up. At first it's normal, then it gets faster and faster, doesn't slow down, it gets louder and louder... Everytime this happens I pull the plug because I fear that the fan will get too fast and then break.

When I then start up again, everything is normal.

Anybody heard of this before?
The fan will not break nor will it go "too fast." Fan speed is controlled by the software, and if there's no software controlling the fan, it will run at full speed as a precaution... it will not break or go too fast, though.

It sounds like on certain startups that your computer isn't starting up correctly... have you had any OS or system issues recently?
Nope I didn't have any problems...

The fan starts to spin faster and faster when I see the grey apple logo on the white background. I don't the system is completely running at that stage.
To be fair, if you've never heard the fan going full tilt, you'd be afraid something would break. In my Powerbook, if the fan went at full speed, I'd be afraid that it would take off!
There may be a small problem developing in that if you are truly unplugging the machine in the middle of start-up, on multiple occasions, well, I don't think the machine likes that.

I would recommend letting it start up, then do all the typical repairs (permissions, CRONs, etc.). As stated, the fan is run by software and it seems somewhere along the way, the software control was affected.
I have the opposite problem, my fan does not come on at all. I have a G4 powerbook (brand new), and have yet to hear the fan activate. Is this a software problem or a hardware problem? how do I chech it out? my computer gets quite hot sometimes, in fact I was burned nast night when I fell asleep with my PB on. interestly enough the worst burns were from the power plug where it rested aagainst my leg. any explanation for this?
I did a little test with a thermometer taped to the bottom of the case and it registered 130 degrees F. seems a bit hot to me. thanks in advance for any help.
mike in MD