CPU fan stop work in periods

Hi, I have
Motherbord - P35-DS3R
CPU: Core2Duo E6750 BOX
Power - 550W

My problem is that somtimes the CPU fan stop working.. I notice that yesterday he stop working.. I shut down the pc and start it again, the fun start working normal.. after that i was working for 5-6h rendering + games and the fun was working fine from 800-1000 RPS.. the temp was 32-35°C.. After that i let the pc to stay on until i sleep for 6 h, when i get up the fun didn't work again and the CPU temp was 45 °C.. the CPU is two weeks old, it have the Box FAN .
I wish to know can this be some software that can control or shut down the fan, voltage problem or the FAN have failure ? or anything else that can couse this problem.

Thanks

 

Hi, Again
I just get back from work, and power the PC
the fan start to work normal, but after 2 min he stop the temp was lake 22 C
Than i try to spin the fan and it start work, just litle toutch on him and he start spining, this happand tree times in 1h , he stop and i will touch it and he will continue with work

Any idea ?
Shood ireplace him ?

 

I would replace the fan. It will stop working sometime soon. Lucky for you, it is easy and inexpensive.

Post back if you have any problems.

E