GX280 - is it the motherboard?

Question

Hi - I have a Dell GX280 which has the loud fan issue.. I have replaced and upgraded the original heatsink w4254 to the G8113 and replaced the original fan w/ same model. The fan is still running at a high speed - w/an above normal noise... Do you have any suggestions on how to fix this... could it the motherboard? if so - do you know what dell replaced the problem boards w? (i.e. model #) I also did a bios flash today A03 to A07... :-0 but the fan is still not very quiet... your suggestions would be greatly appreciated.thanks!