i am experiencing a problem where my mobo can only detects fan speed of the Achilles 12cm fan at 1300-1500rpm sometimes. most of the times it detects 0rpm. why is that? when i use the original intel stock cooler i have has no problem like this. seller said that its normal for fans like these to report 0rpm. anyone experiencing the same problem?

i've tried connecting it to the System Fan 2 power pin only to come out with the same result. i'm thinking of getting the seller to replace it.

Gigabyte GA-EP45-UD3R. i've tested coolermaster 12" fan and it's rpm can be detected.