check that there no wire from the cpu fan plug jamming the fan on the cpu. if this is an after market fan setup see what the fan sped is rates..slow/max speeds.if the fan does go to 400 rpm then in the asus bios you have to change the fan speed from 600rpm the low end warning to 400. also make sure that all the pins are connected on the fan plug and your using the cpu_fan not the cpu_fax/aux. some newer mb have two cpu fan plugs for the newer sealer water kits.
Thanks for the replies. There is nothing blocking the fan and its up around 480RPM now after being on for 15 mins. I can turn down the low speed limit if that will fix it but if the lowest setting is 700RPM does that mean theres something else wrong.
I changed the other fans to be connected to motherboard and I'm getting a similar issue in the BIOS. Picture shows what I mean.
The temps at idle are fine, so maybe the MOBO is misreading the fan speeds? Perhaps run a stress test and note the highest temps to make sure the fan is cooling properly. If it is and the warnings continue, it should be fine to re-set the BIOS limit.
OK Thanks I'll try that. In your opinion whats the best way to perform a stress test. I havent installed an OS yet but I can do that now that I know I can go ahead without doing damage. Thanks for the help Ill be back when I have OS and drivers installed.