I have an i5 2550k a p8z68 mobo, and a Corsair h100 liquid cooler.

As of last night the CPU started throttling and I guess overheating after 4 years no issues. Whatever, i tried reapplying new TIM/Thermal paste but motherboard still says 90 Celsius in a matter of minutes.

Oh, and my motherboard started spitting out a "CPU fan error" post code. What should I do now? The CPU didn't even feel hot. The cooler is definitely running and flowing.

Any ideas?

  • You say the cooler is definitely running and flowing. Do you mean the fans are working on the radiator too? Or can you just feel the slight vibration from the liquid? – DrZoo Jun 2 '16 at 16:00
  • I mean i feel some movement in the tubes, and the fans on the radiator are working fine. – Dont Jun 2 '16 at 16:37
  • Are you sure the CPU is overheating? The problem may just be that the fan is not being detected. – David Schwartz Jun 2 '16 at 16:41
  • Yes, mobo says 90c. – Dont Jun 2 '16 at 16:57
  • 1
    Ok issue is fixed. The cooler was the issue. Stock cooler is working fine. How to fix water cooler? – Dont Jun 2 '16 at 18:10

When you see the error message "CPU FAN Error" in POST, it means the system doesn't detect the FAN.

You can refer to the steps below to resolve the issue.

  1. Please make sure the CPU FAN is installed on the right position of the motherboard and twist the screws tightly

  2. Ensure that the CPU FAN cable is securely installed to the CPU_FAN connector instead of the CHA_FAN.

  3. If you install the other brand of CPU FAN with lower revolutions speed, the system may not able to detect it correctly. You can try to set "CPU Fan Speed Low Limit" to 200 RPM in BIOS configuration.

    • "CPU Fan Speed Low Limit" appears only when you set the CPU Q-Fan Control to [DC Mode], [PWM Mode], and [Auto]. For those early versions, you need to set the CPU Q-Fan Control to [Enabled], [Advance Mode] or [Auto].
  4. You can set Monitor->CPU FAN Speed to [Ignore] if you don't want to open the computer case.

*You can set CPU FAN Speed to [Ignore] if your computer coming with water cooling system without fan.

  1. Update the BIOS to the latest version.

Hope this Helps!

  • Thanks, thats from asus´s site i have tried all of that. My cable for the cpu_fan header feels loose or wobbly but that shouldnt matter if its broken. The header isnt at all linked to the cpu temp sensor right? – Dont Jun 2 '16 at 16:02
  • If all else fails take it to service. – EliteGaming Unleashed Jun 2 '16 at 16:08
  • The H100i supplied back plate should be snug to the motherboard not loose at all, and if it is loose it is improperly installed and not allowing the clamping pressure is was designed for – EliteGaming Unleashed Jun 3 '16 at 11:33
  • I dont have an h100i. I have an h100. – Dont Jun 4 '16 at 21:43

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