I recently purchased a T420 on ebay, and I like it a lot, except for the annoying fan that seems to insist on being on a relatively high setting all the time.

During a Google search, I came across this:

I set up thinkfan as suggested, but now my fan is even MORE annoying, sometimes going to a higher speed than I've ever heard before. The temperatures stay within safe ranges, though. Sometimes the fan will slow down more often with thinkfan and the above configuration, but the fan now seems to change speed every few second and it's distracting.

My first question is, does anyone know why thinkfan is even necessary in the first place? Every laptop I've ever used so far uses the BIOS to control the fan speed, the OS has nothing to do with it. I'm not sure why that is the case with Lenovo. Second, the idea of thinkfan scares me a bit, and I have a hard time trusting it.

I'm hoping someone here also has a T420 and has already figured out the great mystery of how to make the fan sane.