[SOLVED] strange cpu fan speed ratings

[j121]

Running a noctua 4 pin pwm fan on a Fujitsu p710 i get very strange fan speed ratings, the cpu fan shows about 345-350 rpm but dont go higher, the system fan shows 160 rpm after running it for a while the temps are very good under load.

When changing cpu fan to a 3 pin noctua fan i get more normal readings, showing 1260 rpm on the 3 pin cpu fan and the system fan gives more normal readings about 800 rpm.

Somehow connecting the pwm fan gives very strange readings but very good temps under load about 55 c on intel core i3 3220. Should i be worried or ignore the false speed readings and keep using the pwm fan? i checked the cooler after turning computer off and its not heated at all so i guess the temps showing got to be wrong?

 

[Barty1884]

With a proprietary motherboard, it's possible it's just not obtaining accurate readings from the PWM fan.

160 seems really, really low to be accurate. Most Noctua's will only spin down to ~300rpm +/- 20%

If a fan were really only spinning at ~160rpm, it wouldn't be maintaining the temps a comparable fan at 800rpm would achieve.

Simply sounds like a misread to me.

 

[j121]

yes i mean since i get that good temps after halfhour on Heavy load. seems like it can handle the 3 pin and the 4 pin system fan and the original system 4 pwm fan and the system fan but when connecting the noctua 4 pin pwm fan both Readings goes crazy. maybe the 4 original 4 pin pwm fan is wired differently than a normal one.

i dont Think i would get temps like 50-55 c under load even if the cpu fan was spinning at 800-1200 rpm so it got be off even if the 3220 isa 55 w cpu.
thanks