CPU fan not deteceted on initial boot up, but boots up on the 2nd time (no fan detected)

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sonorityscape

Reputable
Mar 12, 2017
29
0
4,530
As the title says, often my my PC won't boot up the first time, but after I turn it off and on again, it always boots up successfully. Maybe about 10 to 20 percent of the time it will boot up on the first try. Would anyone know what causes this? I get the no CPU fan detected message. I have my CPU fan connected into the main header, and if I remember correctly from when the cover was off, sometimes the fan would not start, but if I nudged it, it would start.
 
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I would think either something wrong with the fan or the motherboard is not supplying power at all (or sufficient power if judging by the nudging) to the header.
I'd either get another pwm fan onto the same cpu header, and clamp it onto the radiator, instead of your fan, or if you have another desktop with a free 4 pin fan header, take your fan from your current PC and plug it into that fan header just to see if it responds correctly.
I wouldn't think it's anything in the bios itself if it starts fine on second boot.
Faulty fan is easy to replace. Motherboard...not so much.
Oh...also do you have a cpu_opt header? Often motherboard nowadays include second cpu header for coolers with two fans. If yes, can you plug your fan into that...
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Sedivy

Estimable
Dec 17, 2016
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3,960
I would think either something wrong with the fan or the motherboard is not supplying power at all (or sufficient power if judging by the nudging) to the header.
I'd either get another pwm fan onto the same cpu header, and clamp it onto the radiator, instead of your fan, or if you have another desktop with a free 4 pin fan header, take your fan from your current PC and plug it into that fan header just to see if it responds correctly.
I wouldn't think it's anything in the bios itself if it starts fine on second boot.
Faulty fan is easy to replace. Motherboard...not so much.
Oh...also do you have a cpu_opt header? Often motherboard nowadays include second cpu header for coolers with two fans. If yes, can you plug your fan into that header instead? That might even be easiest of all options to test.
 
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blurpro395

Commendable
Sep 15, 2016
28
0
1,540
I had a similar problem, my PC also wouldn't boot the first time (always took 2-4 tries). Updating the BIOS seemed to fix all boot problems for me. Just an important suggestion before you start to RMA parts.
 
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