Case fans sometimes not working

[jQuery]

Hi,

My case fans doesn't work sometimes. When I startup my computer, they do not go on.
Case: Sharkoon VG4-W
Motherboard: Asrock 960GM-VGS3 FX

I can control my case fans in the BIOS.

Someone knows why?

-Edit-
I forgot to say, when the computer start up and the case fans does not work, they go on after a few minutes

 

[Plumboby]

check all your fan connections are pluged in firm or you case fans packing up go buy a new set be safer option

 

[jQuery]

check all your fan connections are pluged in firm or you case fans packing up go buy a new set be safer option

They are connected

 

[jQuery]

This is still not fixed. The problem is, 80% of the time when I startup my PC the case fans work ok. And 20% of the time it's not working and my CPu* hits 66+ C.

*AMD FX-6300