Question CPU fan is not responding well

Dec 11, 2019
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After a bad graphics card update, I restarted my pc and did a system restore. After that I noticed that the cpu fan (PWM) isn't spinning when it should be. The behavior is it would spin a couple seconds after startup then instantly stops spinning. The LED is always on. I think at one point it started spinning for a second while in the BIOS then stopped completely, and I wasn't able to replicate this behavior with the same settings.

I also checked the BIOS and found out that it's not reading the fan from CPU fan connector. However, I connected one of the case fans (DC) to the CPU fan connector and it worked fine. I also connected the CPU fan to the SYS fan connector and that worked fine too. I did a BIOS reset and nothing changed. I also did a BIOS flash and nothing changed. When I set my CPU fan to DC and full power, it doesn't spin at first, but after a minute or so, it starts to spin (500-1500 RPM), and it doesn't respond to the full power option in the BIOS.

Could it be the cpu fan connector that's messed up or the cpu fan header? This is my first build, and I'm afraid that I've already broke something.

Specs:
MSI MPG x570 Gaming Pro Carbon WIFI
AMD Ryzen 7 3700X 8 Core 16 Threads
AMD Wraith Prism Cooler
Corsair RMX 750X 750Watt 80+ gold certified
Crucial Ballistix Sport LT 3200 MHz DDR4 DRAM Desktop Gaming Memory Kit 16GB (8GBx2)
WD Blue 3D NAND 1TB Internal PC SSD - SATA III 6 Gb/s, M.2 2280
GIGABYTE AMD Radeon RX 5700XT Gaming OC 8G Graphics Card
 
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Dec 11, 2019
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First: make sure BIOS fan profile is configured for a PWM fan, not VOLT controlled fan.

Second: try another fan, like a chassis fan, on the header to see if it will work correctly. Make sure it, too, is PWM (4 wires) and not VOLT controlled.
The CPU fan profile is defaulted to PWM settings, and I've been using these settings until the bad update mishap. After that, the fan stopped spinning and won't spin under these settings even when the CPU gets >50C. I tried doing full power but it's still not spinning. I checked the Board Monitor while in these settings and it said that the CPU fan connector is disconnected, even though the fan is plugged in with the LED on.

I don't have another PWM fan with me, I'll buy one later and see if the problem persists.
 
GO to bios and reset to default settings. If this dosn't clear up the problem, turn off the pc, remove plug from wall, pull the cmos battery out, wait ten minutes and replace battery. Power back up and see if it clears up. If not, update the bios to newest one and see if that helped.
 
Dec 11, 2019
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GO to bios and reset to default settings. If this dosn't clear up the problem, turn off the pc, remove plug from wall, pull the cmos battery out, wait ten minutes and replace battery. Power back up and see if it clears up. If not, update the bios to newest one and see if that helped.
I've already reset the BIOS and even flashed the BIOS to the latest update and nothing's changed. I'll try removing the cmos battery though, but I'm just afraid of damaging my motherboard, as it is my first build.
 
I've already reset the BIOS and even flashed the BIOS to the latest update and nothing's changed. I'll try removing the cmos battery though, but I'm just afraid of damaging my motherboard, as it is my first build.
Removing the cmos battery will reset everything and set the bios to a lower bios number. It will not harm your motherboard. If your fan works properly after this then it is safe to update the bios to the newest one.
 
Removing the cmos battery will reset everything and set the bios to a lower bios number....
That might be the effect of a CMOS reset with some dual-BIOS boards but I do not believe OP's board has a dual BIOS. Resetting CMOS, even with a battery-pull, won't change the revision of his BIOS. It will remain the same, just with all CMOS setting locations reset.

But resetting CMOS is definitely good idea. Also using the 'set BIOS to default values' option from within BIOS...in the save settings screen.
 
Reactions: mortemas
Dec 11, 2019
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I've replaced the CMOS battery, fan still isn't spinning. I'll get a PWM case fan later and see if the problems lies in either the cpu fan or the mobo.
 
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Dec 11, 2019
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Just for testing purposes, in case you've not already tried it.

Also set the BIOS fan setting to be Voltage controlled to see how it works.

ALSO connect the CPU cooler fan to a case fan header and try it there.
I’ve already tested it out, when I changed from PWM to DC and on full power, after a while it started to spin albeit very weakly (500-1400 rpm). When I connected the fan to the sys fan header, it works just fine and rpm matches the other case fans.
 
I’ve already tested it out, when I changed from PWM to DC and on full power, after a while it started to spin albeit very weakly (500-1400 rpm). When I connected the fan to the sys fan header, it works just fine and rpm matches the other case fans.
definitely try a case fan on the CPU header if you can. with voltage maxed out at all temperatures and the fan barely running it sounds like the driver could be flaking out on the motherboard.
 
Dec 11, 2019
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definitely try a case fan on the CPU header if you can. with voltage maxed out at all temperatures and the fan barely running it sounds like the driver could be
Used a DC case fan on the cpu fan header and it’s also working fine, buying a PWM case fan to make sure it’s working as well.
 
Dec 11, 2019
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Update: For whatever reason, before I got my PWM fan to test it out, while I was in the BIOS settings doing absolutely nothing my CPU fan started to sputter for a few seconds, then began to function normally. It was following the smart fan controls after that.

I also tried out my PWM fan when I received it on the CPU fan header and that's working fine as well. I was so confused I basically accepted it as a miracle.

But there are some observations I noticed after this. While playing Ghost Recon Breakpoint for a while, the CPU fan decides to stop when doing something not intensive (e.g. opening up in-game menu). Usually it would just spin at lower speeds when playing for a first few hours but after that it would stop spinning almost immediately. Wasn't sure what was going on, so I tried configuring my fans in the BIOS to spin a bit more.

Maybe it's the motherboard that's not being too great? I recently watched a review on the MSI MPG x570 Gaming Pro Carbon WIFI and that this mobo gets hot really fast.
 
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