so the fan came with 4-pin molex and 3-pin header connections. motherboard has 4-pin headers. when connecting the fan via mobo (sys_fan3), i get nothing, no spinning. when connect to psu of course i get full throttle. when connect fan to header and psu, fan is full throttle and BIOS will read fan speed properly. why wont fan run if only connected to mobo alone? fan headers are enabled in BIOS and set to .75pwm / C. which my understanding means that at minimum fans should spin up right after boot, no?