Rear Fan stops after boot

[Cryption]

Hi today I've noticed that when my computer boots up my rear fan works fine but as soon as it boots into windows (7) the fan stops spinning and to get it working again I have to go into the Asus control panel then into fan xpert and click chassis fan to make it start working again. Note as well then after awhile it will stop spinning again and will have to do the same process again to get it working again.

If you can help me out with this issue I will be most grateful

Notes;

Motherboard = p8z68-v pro/gen 3
Case = Coolermaster HAF 922

PS. The rear fan also has a slight clicking/ buzzing sound to it which the other fans don't, is this normal?

Thanks

 

[setter]

Have you enabled chassis fan control in bios, (under hardware monitoring). Could possibly be a faulty fan as you say it's clicking/buzzing. Can you try another of your case fans on the fan header?

 

[Cryption]

Just checked my bios and it is indeed enabled and states its running at 800 rpms