Some motherbds have, in the bios, setting for how the fan behaves and when it should come on or how fast it should run... things like that.
Check you bios to see if you can set it to always on or full speed, something like that.
What motherbd and model do you have? I can download the bios and look thru it if you don't see the settings. Not all motherbds have them.
Its a gigabyte 970A Ds3