Hey there,

So my case has 3 fans in it. 200mm in the from and 2 140mm in the back via a push/pull config on an Corsair H90 radiator.

The two case fans are 3 pin fans connected to a fan controller on the case that is powered by the PSU and a 4 pin PWM controller that connects to the mobo. The third fan is a 4 pin PWM fan that came with the H90 connected directly to the mobo.

I noticed something when booting up and restarting the pc in regards to the Corsair fan. During boot it spins up then almost immediately spins down to a full stop, the time it’s stopped varies but I’ve seen it stopped for as long as 6 seconds before it kicks back on.

The 2, 3pin case fans do not do this.

The Corsair fan is plugged directly into the motherboard while the 2 case fans are plugged into a fan controller that is then connected to the motherboard and PSU.

My assumption is that the 2 case fans never spin down because of some interaction with the controller. But the Corsair fan spins down to a stop due to the motherboard. From what I’ve read during bootup fans directly connected to the mobo run at full speed but then adjust to their set speed when the BioS kicks in?

Does this sound like what I’m experiencing? A full spin up right at boot then the fan completely stops, the motherboard then spins the fan back up after a few seconds when it recognizes the fan? This happens if I restart the computer as well (which I assume is treated the same as a bootup process).

Thanks in advance. I know this question is probably a silly one.

bcavnaugh 
As far as the Corsair H90 when you use it's own PWM Fan Connector the Fans Spin at 100% on start up or Boot up and then what ever you set them to in the Software set the speed, this is also saved in the Corsair H90 also the Pump Settings are saved.

See this is where my question comes into play. The 140mm Corsair fan is a 4pin PWM. It does in fact spin up to max speed on bootup or during a restart but then it doesn’t just slow down to its default speed (which I believe is 60%). It hits full speed then completely stops for up to 6 seconds during post (could be 1 sec, could be 6) then as the computer gets through the initial boot stage the fan THEN spins back up to its set speeds.

So the confusing part is the fan completely stopping for a handful of seconds.
I understand it should start at full speed and then settle to its set speed but it stops completely inbetween that process.

Outside of a boot or restart I don’t see this happening during the computers standard use so maybe it has something to do with how my mobo handles PWM fans during post.
Motherboard is an: Asus Z170 pro gaming. For the record.

I’m not using any Corsair program for my fans/pump. It’s just all through the BioS.

Quick google search shows that the H90 does not work with Corsair Link as posted by a Corsair rep. However I have the pump running at 100% speed through the BioS as intended.

In regards to the fan, I actually figured out what was going on last night. Apparently the fan was never set to PWM in the BioS, it was set to DC. Don’t know why that would cause the fan to completely stop for a few seconds on bootup but it was. I changed it to PWM, set a fan curve and now the fan no longer stops.

I guess maybe having a PWM fan set to DC was confusing the system or something, why is beyond me.

Cool GTX
Glad you got it sorted - changed MB fan header to PWM

I’m replying to my own thread as it’s a question about the same fan I resolved. If this is against the rules feel free to lock it and I apologize.

Originally I had an issue with a PWM fan being set to DC causing it to full stop on bootup. It’s been set to PWM since and I haven’t had the problem.

I’ve now noticed a buzzing sound coming from the fan, the buzzing is louder and more audible with the fan set to PWM. If I set the fan back to DC the buzzing is still there but it’s quieter. However the fan stopping issue returns so not ideal.

The buzzing from the fan isn’t bothersome I’m just curious why it might be doing this(?). It’s a 4pin fan, but the sticker on the fan reads: Corsair Brushless Fan 12v DC.

Does this mean even though it has a PWM header it should be run in DC?

However to match the RPMs... in DC the fan speed is at 60% and in PWM about 40% in the BioS. These settings keep them at 900-1000rpm but have a 20% difference depending on the mode and I don’t know why...

Is there still a difference in PWM and DC that may cause the louder buzzing? Again I still hear it when it’s in DC mode but it’s quieter. I’m just curious if I’m hurting the fan in PWM hence the louder buzzing or if maybe I just got unlucky with manufacturing.

My thought is that in PWM it only has to run at 40% vs the 60% in DC to reach the RPM I want. So maybe it’s drawing less power producing a louder buzz? I know some fans and pumps get noisier the lower they are.

I’ve contacted Corsair but figured I’d try here too, thanks in advance.