Question Fans randomly don't start at boot

criticalsmile7

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My motherboard living its own life. I discovered this issue 4-5 months ago, I believe after CPU and cooler upgrade. Very rarely after bootup my CPU hits 100 degrees and system freezes with BSOD. I did not know why that happened for a long period of time, so I just keep restarting my PC after each BSOD and forget about that issue for 2-3 weeks. This happened like 6-7 times in 4-5 months, completely randomly, sometimes without BSOD, sometimes with error message "CPU overheat" after restart. My system works completely fine when that happened, like nothing were happened at all, just ALL fans were not spinning until 100degrees cooked up my CPU and the system freeze.

Today I finally realized that my PC is too quiet after boot-up, so I quickly checked CPU fans, and I was horrified, ALL FANS of my PC did not spinning: CPU, GPU, 4x case fans, all were dead. Motherboard was working just like everyday. The only thing is it was showing 00 instead of cpu-temp in led indicator on Motherboard.

Motherboard: MSI MEG Z490 UNIFY (MS-7C71)
CPU: I7-10700K
GPU: GTX1080TI
RAM: DDR4 G.Skill F4-3200C16-8GVKB 4x8gb

What I did:
  • disabled all sleep features
  • disabled fast boot
  • BIOS update to the latest version
  • CMOS clear
  • BIOS reset all settings
Currently I'm angry with myself that I didn't discover this earlier, because my CPU now is in a very bad shape, hitting 75 degrees when browsing with many tabs. What do I need to resolve this?
 

mikewinddale

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First, it's not surprising that your GPU fan isn't spinning. The GPU fan only spins when under load, not when idle. But the fact that the rest of your fans aren't spinning either is obviously a problem.

Anyway, the first thing I'd do is buy a fan hub that is powered directly from the power supply. That should ensure your fans all spin regardless of what your motherboard wants.

You don't want to be using your computer while the fans aren't spinning. So the first priority is to stop using your computer until you've got the fans working again, using a PSU-powered fan hub.

Once you've got all your fans spinning, you can start experimenting with your computer to find out why the fans aren't spinning when they are connected to the motherboard fan headers.

Keep one fan plugged into a header, so that you can use it to test the effects of different settings. Keep the majority of your fans powered from the power supply, so that your system is still being cooled while you experiment. For example, keep one case fan plugged into the CPU header while all the rest of the fans are powered from the power supply. Then, use HWiNFO64 to check all your motherboard's sensors. See if any of the temperature sensors look wacky. Perhaps one of the temperature sensors has malfunctioned, so the motherboard mistakenly thinks the temperature is lower than it really is.

You can also see what happens if you go into your BIOS and change the fan speed curve. Set the fans to spin 100% regardless of temperature, and see what happens. If the fans spin, then the problem is with the temperature-based fan curves. But if the fans don't spin even when they are instructed to spin at 100% regardless of temperature, then it's probably a problem with the fan headers themselves.
 
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mikewinddale

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I'm looking at your motherboard manual, and it says you have to manually switch between PWM mode and DC mode for all fans. There's no "auto" setting. So make sure your fans are all set to the correct mode.
 

Paperdoc

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I echo JohnBonhamGhost's query "what are you using to control their speeds? "

The NORMAL way for ALL fans at a start-up IF they are under automatic control is that the all start up at full speed, then some seconds later slow down to what is needed. HOWEVER, you do have an option to override that and force any or all fan headers to run the fan at a fixed setting. VERY often people set this to slower than max just to be quiet, not worrying about lower cooling. BUT if you do this and it is set too low, the fans may never start!

So, how do you have your fan headers set IF they are connected to mobo headers? And if not, provide details HOW they are connected and what settings you are using.
 

criticalsmile7

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Thanks for your replies guys.


what CPU cooler?
what CPU & case fans, where are they located, how are they connected?
what are you using to control their speeds?
what are you using to monitor temperatures?
CPU cooler: Noctua nh-u12a
Both CPU fans connected to PUMP_FAN1 slot on MB, because I can control them via PWM from that slot (in BIOS). I believe I can not do that via CPU_FAN slot, that's why I'm using PUMP one.
3 front Case fans: NZXT RF-AF12C-RB, they are 3-pins fans, connected to 4-pin extender cable that is connected to SYS_FAN4 slot.
1 back case fan is NOCTUA NF-S12B, connected to SYS_FAN2.
BIOS controlling their speed, never used an app for that, I manually added temp/speed curves for all of them (including CPU).
MSI afterburner is used for temp control.

Can 3x / 3-pins front case fans, that are wired to 4-pin cable and then to one slot at MB, casually turn off all _FAN slots on MB?


PSU: make, model, wattage, age, condition?
Heavy use for gaming, video work, or even bit mining?
PSU: Raidmax Cobra RX-1200AE-B
Bought 09.2018, 1200w.
I'm using PC for games and CPU-heavy works only.


First, it's not surprising that your GPU fan isn't spinning. The GPU fan only spins when under load, not when idle. But the fact that the rest of your fans aren't spinning either is obviously a problem.
Anyway, the first thing I'd do is buy a fan hub that is powered directly from the power supply. That should ensure your fans all spin regardless of what your motherboard wants.
You don't want to be using your computer while the fans aren't spinning. So the first priority is to stop using your computer until you've got the fans working again, using a PSU-powered fan hub.
Once you've got all your fans spinning, you can start experimenting with your computer to find out why the fans aren't spinning when they are connected to the motherboard fan headers.
Keep one fan plugged into a header, so that you can use it to test the effects of different settings. Keep the majority of your fans powered from the power supply, so that your system is still being cooled while you experiment. For example, keep one case fan plugged into the CPU header while all the rest of the fans are powered from the power supply. Then, use HWiNFO64 to check all your motherboard's sensors. See if any of the temperature sensors look wacky. Perhaps one of the temperature sensors has malfunctioned, so the motherboard mistakenly thinks the temperature is lower than it really is.
You can also see what happens if you go into your BIOS and change the fan speed curve. Set the fans to spin 100% regardless of temperature, and see what happens. If the fans spin, then the problem is with the temperature-based fan curves. But if the fans don't spin even when they are instructed to spin at 100% regardless of temperature, then it's probably a problem with the fan headers themselves.
That's completely true, GPU fans start only after reaching a certain temp. Thanks for so the detailed advice, I'll try that.


I'm looking at your motherboard manual, and it says you have to manually switch between PWM mode and DC mode for all fans. There's no "auto" setting. So make sure your fans are all set to the correct mode.
I already did that long time ago when I bought the new case. My system worked completely fine until I upgraded CPU and CPU-cooler. I also did change my PSU because my old one did not work well with GPU for some reason, but honestly I'm not sure what of these actions provoked my current situation.
 

criticalsmile7

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I echo JohnBonhamGhost's query "what are you using to control their speeds? "
The NORMAL way for ALL fans at a start-up IF they are under automatic control is that the all start up at full speed, then some seconds later slow down to what is needed. HOWEVER, you do have an option to override that and force any or all fan headers to run the fan at a fixed setting. VERY often people set this to slower than max just to be quiet, not worrying about lower cooling. BUT if you do this and it is set too low, the fans may never start!
So, how do you have your fan headers set IF they are connected to mobo headers? And if not, provide details HOW they are connected and what settings you are using.
Yep, they all start with not full but much higher speed that they are working just a few seconds later. All my curves start from 20-30% of speed, I made that settings long time ago after I bought new case, and currently in my case there are only 2 possible situations: they're all work just fine or none of them work.
 
I believe I can not do that via CPU_FAN
sure you can, they wouldn't be 4pin headers if they didn't allow PWM control.
it's always recommended to use the CPU_FAN header for CPU cooler's fans.
some boards won't even post without a signal to the CPU_FAN header.
but if the PUMP_FAN slots work just as well, it shouldn't really matter.

i have seen some instances where fans controlled via the BIOS can sometimes "lose" their profile when loading into Windows.
sometimes it appears to be software conflicts, sometimes by design, others maybe just a bug.

try using the MSI motherboard control software or something like SpeedFan to setup new fan curve profiles inside of Windows that are set to run at startup.
see if the issue with them not starting up remains.
 
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Paperdoc

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So you set ALL of your fans (CPU cooler and case vent) to run at 20 to 30% speed when the system is cold (at start-up). And they do as they are told - start fast for a few seconds, then slow down a lot. And then from time to time they all STALL!. Well, go back into your custom "fan curves" and set the MINIMUM speeeds (t low temps) a bit higher so they don't stall.
 

criticalsmile7

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Sep 3, 2018
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So you set ALL of your fans (CPU cooler and case vent) to run at 20 to 30% speed when the system is cold (at start-up). And they do as they are told - start fast for a few seconds, then slow down a lot. And then from time to time they all STALL!. Well, go back into your custom "fan curves" and set the MINIMUM speeeds (t low temps) a bit higher so they don't stall.
If I got this correctly and they stalled at min speed, after some amount of force they will spin again, right? But they're just dead, check the vid
View: https://youtu.be/iXbT7Ppirko
 

Paperdoc

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You are right about that. Those fans in your video certainly appear to have NO power on them. That could happen one of two ways. You MIGHT have set the minimum speed at lowest temps to near-zero speed. OR, on some mobos there actually is an option for each header to allow the mobo to shut the fan off at low temps, rather than keep them running at a min speed. Look for that and IF you find it, set it NOT to shut off any fans. And make sure that the fan controls are enabled, even though they are using your custom fan curve.
 

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