Macbook2,1 late 2006 fan not spinning

My macbook is very hot, the fan never starts. I tried some softwares like Fan Control 1.2, scmfancontrol 2.4 and Macs Fan Control but each of them is giving me always 0 rpm on the main (right) fan…

Why? What can I do?

The system is a very fresh install of Lion, updated to the last, 10.7.5

Ps: I remember that before going to reinstall it, a manual control on the fan was working...