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Asus Motherboard CPU Fan Error

Hey guys,

Just built a new pc (Asus Z170-AR mobo, Cryorig R1 Ultimate cooler, Phanteks Enthoo Evolv ATX case)

Have been running into the this message during startup "CPU Fan speed error detected. Ensure that the CPU fan is properly installed on the CPU_Fan header or adjust/disable the Fan Speed Low limit option in the UEFI BIOS."

This occurs when I plug the Phanteks' PWM hub (with all the chassis fans) into the CPU fan header (which the mobo manual advises to do) whilst the CPU cooler into the CPU Opt header. The Asus website (http://www.asus.com/support/FAQ/1015061/) says to set the "fan speed lower limit" to Ignore but this doesn't work for me. What works is setting the "CPU Fan Speed" to Ignore instead (http://imgur.com/hTAEHw1)

Is this a suitable compromise? I want to take advantage of the PWM hub.

Another solution is actually plugging the cpu cooler into the CPU Fan header whilst the PWM hub into the CPU Opt header. How do I find out whether this Opt header has true PWM signal modulation and doesn't modulate the RPM by voltage?

Help much appreciated.
6 answers Last reply Best Answer
More about asus motherboard cpu fan error
  1. use one of the 4 pin system fan headers on the mb. for the power to the case fan hub. you need to plug in the cpu fan into the cpu port or you get that message every time.
  2. 1 x CPU Fan connector(s) (1 x 4 -pin)
    1 x CPU OPT Fan connector(s) (1 x 4 -pin)
    4 x Chassis Fan connector(s) (4 x 4 -pin)

    three pin headers are non pmw ports if there all 4 pins any of them should work.
  3. I had the same problem I plugged my CPU cooler into the normal CPU_FAN slot and my fan hub into the CPU_OPT. Or you could plug it into one of the other 4 pins on the mobo
  4. smorizio said:
    use one of the 4 pin system fan headers on the mb. for the power to the case fan hub. you need to plug in the cpu fan into the cpu port or you get that message every time.


    Great, thanks. I had done this initially but was afraid that the CPU Opt 4 pin header was non-pwm.
  5. broidk said:
    I had the same problem I plugged my CPU cooler into the normal CPU_FAN slot and my fan hub into the CPU_OPT. Or you could plug it into one of the other 4 pins on the mobo


    Thanks, it works perfectly when I do this; I was just afraid the CPU_Opt was non-pwm. Can I ask whether or not you used the Asus fan auto tuning in the AI Suite or did you set it yourself manually (low rpm for low cpu temps).

    Also, with the hub in the Opt header, I can see that it is detected alongside the CPU fan (http://imgur.com/mR9RO29; bottom right corner) yet I can't seem to manually tinker with it in fan expert 3; shows all chassis fans as unknown. Do you know how I can get CPU_Opt to appear in fan expert?

    EDIT: I switched the hub from CPU_Opt to Cha_Fan4 (assuming it's still PWM since it's 4-pin as well) as I believe the software grouped CPU_Fan and CPU_Opt together which makes sense; all case fans ramped up when testing only CPU Fan itself. What sort of manual settings have you got yours running at, or how might I determine these for myself? (http://imgur.com/LbTDRGA)
  6. Best answer
    My BIOS looks different but I have mine grouped with my CPU right now and it works perfectly fine I game on ultra and never run to hot. You can keep the auto settings honestly. Or make it so it's however you want silent or just keeping your PC cold asab.
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