My PC became unusually slow while I was using it and then shut down. When I tried to start it again, the motherboard reported: "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." I disabled the warning, but a few minutes later I heard an unusual noise inside the case and shut the computer down because I was worried I had damaged something. I'm using a Corsair H90i liquid CPU cooler. The warning disappeared on a later boot, but I'm still concerned that the pump or radiator fan may be failing. What should I check before using the PC again?
3 Answers
Because the PC slowed down and shut off before the warning appeared, overheating is a real possibility. Reseat the cooler and its power connections, inspect the cables for contact with the radiator fan, and confirm that the pump is receiving power. If the pump is dead or the temperature climbs quickly, stop using the computer and repair or replace the cooler. Disabling the warning only hides the symptom; it doesn’t solve a cooling problem.
Don’t treat the disappearing warning as proof that everything is fixed, and avoid disabling the fan-speed limit until you know the cooler is working. With the side panel removed, briefly start the PC and observe the radiator fan. Do not put your fingers into a powered fan; if the system is off, you can gently check whether a fan blade is jammed, but don’t force it. A wobbling or rattling fan should be replaced, while a grinding or buzzing sound could indicate a failing pump or fan.
That warning usually means the motherboard isn’t detecting a proper speed signal from the CPU cooler. Since you’re using a Corsair H90i, check both the radiator fan and the pump connection. Make sure the pump or its tach cable is connected to the CPU_FAN header, unless your motherboard’s manual specifically recommends another header. Also verify that the radiator fan is connected to power and is actually spinning when the system starts.
I restarted it once and the warning was gone, and the computer seemed to work normally, but I’m still worried because of the noise.
The CPU temperature should also be checked in the BIOS or with monitoring software. If it rises rapidly toward unsafe temperatures, shut the computer down immediately rather than continuing to test it.