I have a very old laptop I'm trying to rehabilitate and use with Debian: it's got an AMD Turion chip and 1G of RAM.  Works fine.  But one annoying problem under Linux: the fan runs flat out all the time.  If the 'sensors' command is correct, the CPU has never gone above 35C, so the fan isn't running like that because of the heat.

I also used this machine recently to run Darik's Boot And Nuke (aka "DBAN") on a hard drive: that's a Linux kernel, and the fan wasn't running full out.  Not sure what that proves, except that the fan doesn't have to run full out under a Linux kernel.

I've installed "lm_sensors," I've installed "fancontrol", I've run 'lmsensors-detect' (which is 'sensors-detect' under Fedora and Ubuntu - I've tried three Linux OSes with essentially identical results).  I've run 'pwmconfig' which tells me "There are no pwm-capable sensor modules installed."  I've written a file into /etc/sensors.d/fan-speed-control.conf that said this:

    chip "k8temp-pci-*"

    set fan1_div 4

(This last at the suggestion of ArchWiki, which says reducing the fan multiplier can make it accessible to Linux.)  But running 'sensors -s' to reload the config is greeted with "Error: File /etc/sensors.d/fan-speed-control.conf, line 2: Unknown feature name k8temp-pci-00c3: No such subfeature known."  On an off-chance I tried "fan0_div" and "fan2_div" but same answer.  This has exhausted most of the mainstream remedies suggested by Google.  At this point I'm stumped: can anyone else suggest ways to get a handle on this fan?