CPU Fan problem

Alright, my stock intel fan is giving me some trouble. When I plug it into the 4-pin header on my motherboard it spins at a maximum of 1200rpm (according to speedfan) and when I connect it to my 3-pin header, it spins at 2400rpm (according to speedfan, and yes it's much louder and I can tell it's spinning faster) My question is, how do I get my fan to spin at 2400rpm when connected to the 4-pin header so I can alternate the fan speed through speedfan? Thanks for any help! :D

there should be a 'smart fan' setting in your bios, it might be running that cause it's not under load, trying to raise the temp/load of your cpu to see if that doesnt increase the RPM but if not try to disable the 'smart fan' feature

Did this, and in the bios it says its running at 2400rpm (and I can tell it's running much faster because it's louder) and it boots into windows at 2400rpm but right when I open speedfan it goes down to 1200rpm and I can hear it get quiter,

Make u plug it in ur cpu fan headerĀ 

It is, because I can still adjust it in speedfan, but it only goes upto 1200rpm :p