Fan too loud -> pmu?

[Raph HP <raph@gmx.fr>]

Hello,

I have a TiBook IV, and to my regret it is faster than the older ones
and with that... louder! Under Linux, the fan turns on after about half
an hour and never turns off. When I unplug the power supply, it turns
off after some time. Then I can re-plug it and it takes a time before it
turns on again. So, my questions are:

What does pmu exactly do? In the documentation, I found that it calls
the script /etc/power/pwrctl. Is that right?

I tried to run pwrctl with the arguments "minimum ac", but it does not
seem to work. How can I use it?

Where can I see in what state pmu is (like "maximum ac", in order to see
if my command worked or not)?

Do I have to try with pwrctl-local?

Thanks a lot for your help, please excuse my bad english

raph