CPU fan issue / overheating

[ricksavery]

I have just installed a new motherboard, cpu (AMD FX6300), psu and graphics card. All running OK then odd rythmical noise from one of the fans.
Turns out the cpu heatsink fan works fine at first then turns off for a second, runs for a couple of seconds and so on . . .
The heatsink is not the stock AMD one and worked flawlessly on the previous cpu (Phenom x2 555 BE).
Any suggestions / advice please? By no means an expert but reasonably savvy at building PCs - which will now be shown to be rubbish!
Thanks for any help
Rick

 

[ricksavery]

Thanks for the reply. Sorry I think I have not explained the problem well.
The computer boots fine and runs for quite a while before the intermittent stopping/starting happens. Temperature starts in the 20s/30s and then when the fan plays up it shoots into the 60s/70s at which point I turn it off, having been warned by the noises from the fan.
The heatsink/fan is Scythe Shuriken Rev.B SCSK–1100 and, as I say, it worked flawlessly with previous CPU.
My theories are either the heatsink is not seated properly (which I think it is) or the fan is faulty (which does not happen at first), but what do I know!
Thanks again

 

[ricksavery]

Thanks for the replies. Heatsink seated OK. Robert_G, I think you have it with the BIOS. A setting (I forget which, but something like SmartFan) was turning the heatsink fan on and off - why i have no idea. I disabled this and it now runs at full speed all the time which keeps the CPU in the 28-32 degrees range, which is fine.
Thanks again