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CPU Fan Error

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Brand new build. Just turned it on for the first time. I got the following error message:


CPU Fan Error!

Press F1 to Run Setup


F1 takes me to the BIOS Settings but there are no details as to the nature of the fan error. I’m using a Corsair H115i Platinum liquid CPU cooler. The two fans on the radiator are spinning. The lights on the CPU pump are on. There seems to be warm air coming out of the radiator fans. BIOS says the CPU temperature is 43C so I assume the cooler is working.


All BIOS settings that I checked look OK but maybe I’m not looking in the right place.


Motherboard: Asus ROG Zenith II Extreme Alpha. CPU: AMD Threadripper 3970x.


I can’t get past this error message so I can’t even install Windows yet.


Any clues or suggestions appreciated!

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seems you forgot to plug the tachometer to the motherboard.


There should be a 3 pin plug you need to connect to the CPU FAN header on the motherboard, so that your bios don't give you that error. It will report the pump speed to the PC


Thanks for your reply!


I actually didn't forget to connect the tachometer plug to the motherboard but apparently I connected it to the wrong header at first.


According to the motherboard manual these are the possible headers (not including the ones that are labeled chassis fans). They are all 4-pin female connectors.


CPU-FAN (Connected to this one first. Fan Error)

CPU-OPT (Switched to this one. Problem appears solved.)





Thanks for your help. You pointed me in the right direction.

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Really? Funny ... my AM4 has that set by default. So does my TR4.

Perhaps that's BIOS dependent rather than a global default, eh?


I use MSI motherboards and their BIOS has all kinds of options for the CPU fan as well as the fan headers.


The MB fan headers are not in use so I have them disabled which is the default.


The CPU fan is enabled but the alarm is not. The Alarm can be set to one of several temperatures.


I can post screenshots of my BIOS if you need clarification or you can find the manual for the MSI X470 Gaming Plus or MSI X570-A PRO on the MSI support pages.

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the fan headers are always all under some sort of fan curve by default, with CPU fan alarm enabled. I have never ever found a mobo that didn't behave in that way, AM4 or 115x.. otherwise you'd cook your CPU on first startup constantly.
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