CPU fan wont start until CPU under load

Hey Everyone, I've been trying to find information on this subject for a few days, so I figured I better sign up and post on the forum.

I just built a new computer and sometimes I will get an error on startup that says I have a CPU fan error. When I look in the case, sure enough, the fan is sitting idle. It will do a little quarter spin (or 8th of a spin) every few seconds as if it's trying to start up but doesn't have enough juice.

It will start up eventually, but i have to put the CPU under load first. I'm not sure if it's the temperature rising that kicks it on or something else. My temps look fine on startup without the fan (usually below 45C) and it's only when it gets above maybe 48 or 50 that it turns on.

My question is - is this normal? I thought CPU fans were always on whenever your computer is on. I've tried plugging the CPU fan into a CHA_FAN slot and it worked fine. I'm also a little weary of doing something like changing the settings to ignore the warning (for fear that one time it might not kick on and burn up the CPU).

I already have an aftermarket CPU fan in the mail which I'm going to test out, but my concern is that it's a problem with the motherboard.

Here are my specs:

Asus z77 Sabertooth
Intel i7 3770 3.4G
GSkill 8g x 2 (1600 mhz ddr3)
WD 1tb HD 64m SATA III
NZXT 850 watt psu

Any help is appreciated.

Brian Harms
4 answers Last reply
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  1. Go into the BIOS and try and find the fan settings, by default it should be set to 'full on' but it may not be.

    It maybe that its a power saving feature thats not working properly, but in either case its best to have it on full anyway.

    You say it 'worked fine' on a Chasis fan header, does this mean that it spins up properly on that header, but doesnt on the CPU fan header?
  2. Hey Galarian, thanks for the quick reply.

    Yeah when I plug into the Chasis fan header and then turn on the computer the cpu fan starts up right away. When I plug it into the CPU fan header and start up the computer it doesn't start up either until the temp is high enough or the load on the cpu is high enough (I'm not really sure which - I'm leaning towards heat).

    I'll try adjusting the BIOS and see what happens.

  3. I think the BIOS were actually set to a powersaver mode or similar. I reset the settings and now the fan boots up just before the "starting windows" screen pops up.

    It's still not instantaneous, but it seems to be consistent and hasn't given me any errors so far. Hopefully that's the end of this thread.

    Thank you for the tip Galarian.

  4. Well thats an improvement at least!

    No problem mate
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