[SOLVED] CPU Fan stops working after POST in a one-month old PC ?

Nov 24, 2022
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Asus Rog Strix z690 E mobo. Noctua CPU fan. everything brand new and has been working fine for a month. This morning, turn PC on and I get the dreaded "CPU Fan Error" message with the invite to fix things in BIOS.

Things I've done...
  • Plugged fan into CPU_OPT instead - same result, fan spins up on power up but then stops completely once POST is complete to never come on again until start up again (it twitches on power down).
  • Plugged fan into Chassis 3 port - runs fine, no probs...but that's not the CPU fan port driven by CPU temps.
  • Plugged another noctua fan into CPU fan port to help troubleshoot
  • Upgraded BIOS to latest version (2103) - that reinstated all the CPU fan error message which I set to ignore again and gave me a new error where the CPU fan error gets displayed. This one says "Your Cooler has been somewhat characterized. Press F1 to enter BIOS" (I say old chap!)
  • Tried manual controls for the CPU fan via BIOS and via windows apps.
  • Sent a support request to ASUS. They're taking their sweet time getting back to me. An A$900 motherboard shouldn't have these issues.
It's not a power supply issue...1000W power supply with headroom for days. Only driving a RTX 3060ti GPU. No spinning drives, just a 1TB Samsung 980 PRO. i7-12700K, 32GB RAM.
It was fine yesterday...just powered on today and fan said "not today".
 
Nov 24, 2022
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Oh...you're never going to believe this!
Turned machine on this morning...mouse not working. The USB bluetooth dongle is plugged into a hub. Thought maybe it's flat, plugged in the charging cable, still no mouse activity. Unplugged dongle from hub and plugged into case port...

...CPU fan starts working again.
 
Nov 24, 2022
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I see you tried manual controls for the cpu fan in bios. Does that include lowering the fan rpm in bios?
Yep. Tried all the various settings (standard, silent, turbo, maximum, custom with various profiles.

Nothing explains why it just decided to stop, and nothing seems to want to get the CPU fan going properly again.
 
Yep. Tried all the various settings (standard, silent, turbo, maximum, custom with various profiles.

Nothing explains why it just decided to stop, and nothing seems to want to get the CPU fan going properly again.
Sorry to be clear I meant in bios under monitor, there is a qfan control setting, you can look at and experiment with dc mode, fan rpm speed , and even set it to ignore fan speed. Did you try those also? The only thing I can add is to try pulling both sticks of your ram, place one stick in and see if anything changes. Other than that, you have troubleshot everything I would have tried. It looks like you may be headed for the dreaded rma for the motherboard.
 
Nov 24, 2022
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Sorry to be clear I meant in bios under monitor, there is a qfan control setting, you can look at and experiment with dc mode, fan rpm speed , and even set it to ignore fan speed. Did you try those also? The only thing I can add is to try pulling both sticks of your ram, place one stick in and see if anything changes. Other than that, you have troubleshot everything I would have tried. It looks like you may be headed for the dreaded rma for the motherboard.
Yeah that's where I was playing with the fan settings. Though the bit that gets me was that it just stopped working for no obvious reason. Fan control is clearly a bios thing and after set up nothing has changed. Asus has come back and said... Yeah... RMA. Looks like I get to tear down the machine and use some more thermal paste (thankfully noctua supplies plenty).
 
Nov 24, 2022
6
0
20
1
Oh...you're never going to believe this!
Turned machine on this morning...mouse not working. The USB bluetooth dongle is plugged into a hub. Thought maybe it's flat, plugged in the charging cable, still no mouse activity. Unplugged dongle from hub and plugged into case port...

...CPU fan starts working again.
 

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