How to set cpu fan speed on e6420, its on 0rpm help!!

Hi, i m having issues to set my cpu fan speeds, the problem is it starts to spinning when the cpu temp raise up to about 65°,  then go up to about 3500rpm and when the cpu cools off, it stops again, i really dont like having the temps going to 65 with only 15% of cpu usage, i want to set my fan to continously spin, but idk how, if anyone know how to do it, pls help me, thx!
pd:i m using ubuntu linux.