One fan always stuck at 100%

[subparSamaritan]

I just put the finishing touches on my new build in which I'm using an Arctic Liquid Freezer II in a push-pull configuration with 4 Noctua NF-A14s. I have the four fans connected to two splitters, with one splitter in the CPU header and the other splitter plugged into the CPU_OPT header. Once I've booted into the BIOS, one of the four fans will run at 100% and will not response to changes. I've swapped out the fan to make sure it wasn't faulty and I got the same result. I've also tried connecting the four fans to the built-in fan hub in my case and connected that to my CPU header, same result. At this point I'm not sure why this would be behaving like this unless there's some kind of arbitrary 3 fan limit per "header", even though the four fans are connected to two different headers. The motherboard is an Asus Crosshair VIII Dark Hero.

 

Any ideas?

[Chrismike]

Are the fans you're using the 3000 rpm ones? because i believe each header of the mobo can only supply 1amp and those ippcs draw .55.

maybe that's causing the glitch somehow.

[subparSamaritan]

3 minutes ago, Chrismike said:

cpu header 2 fans and cpu_opt 2 fans as well... should be fine. which fan isn't running? what troubleshooting have you tried? have you tried isolating the problem like running the fans separately?

If all fans are working fine, are the fans you're using the 3000 rpm ones? because i believe each header of the mobo can only supply 1amp and those ippcs draw .55.

The fans max out at 1500rpm, so I don't think this is a power supply issue. The issue isn't specific to one fan, it's just that when I have all four of these types of fans plugged into the motherboard, one of them refuses to go below 100%. I've already replaced the fan that currently does this with a 5th NF-A14 and it's the same result. When I switched from plugging into my motherboard headers to plugging into my powered fan hub, it was a different fan this time that was always at 100%, so it seems to be an issue with the motherboard? 

[Chrismike]

i would think so too....when does it run at 100%? while tuning it in bios or when windows run?

 

 what do you mean it refuses to go below 100%? You're actually unable to set the fan curve below 100%?

 

say, set it to 50%, does it show 50% in the curve but displaying max rpm? OR in the bios it's set to 50% showing 50%rpms as well but you can physically seeing and hearing one of the fans working at 100%?

 

sorry for the questions.....point is you're using a splitter and one fan should only be slaved to the other. without the splitter the fans are working fine right?

 

maybe the wiring for splitter is bad? (wouldn't explain why the 100%running glitch is randomly changing through the fans though).

[subparSamaritan]

It runs at 100% no matter what I'm in, BIOS or Windows, and what I mean by that is that one of the fans is always running at max RPM (loud as hell), even if I set the fan curve for the other fans to like 20%. In the BIOS they all show up as CPU Fan because I have the two splitters plugged into CPU_FAN and CPU_OPT, so I can't get separate curves for each pair of fans, but basically one fan just doesn't listen to what the BIOS fan curve is telling it. 

 

I don't think the splitter would be the issue, but I do have a third splitter on hand so I'll swap it out and see if that changes anything. 

[subparSamaritan]

So I've just confirmed that the splitter cable isn't a factor. Also, I've noticed that not only does a 4th fan plugged into one of the two CPU headers run at 100%, but I get a CPU Fan Error when booting up, but only with four fans. Three fans? No error. Only when 4 are plugged in.

[Chrismike]

Yup. I’m out of ideas i have an aorus board...curve for cpu opt is different from the cpu header. So that’s no help .

 

can you set or put it in a different header(maybe fan1 header) and assign the fan1 header to react to the cpu temp? Won’t work if you can’t reassign the fan1 header to the cpu temp

[subparSamaritan]

Yeah currently I have two fans going into my Fan Header 1 instead of my CPU and that works fine, just nowhere near as elegant as having all four of them in my CPU header. Still genuinely curious if this is some sort of hardware limitation I'm running into because you're really not supposed to power more than 3 fans off of a single header.

[LogicalDrm]

How are you able to monitor 4 fans speeds with 2 mobo headers? Splitter only reports RPM from one fan.

[subparSamaritan]

5 hours ago, LogicalDrm said:

How are you able to monitor 4 fans speeds with 2 mobo headers? Splitter only reports RPM from one fan.

I'm not, I'm able to physically see and hear that one of the four fans is spinning at or very close to 100% while the others run at whatever speed I set them to through the CPU fan header curve in the BIOS. 

[LogicalDrm]

9 hours ago, subparSamaritan said:

I'm not, I'm able to physically see and hear that one of the four fans is spinning at or very close to 100% while the others run at whatever speed I set them to through the CPU fan header curve in the BIOS. 

Well I can say it's not the issue with fans not receiving enough power, the effect would be quite the opposite. Sorry if this was asked already, but have identified whether it's CPU _FAN or CPU_OPT where this happens?

[subparSamaritan]

1 hour ago, LogicalDrm said:

Well I can say it's not the issue with fans not receiving enough power, the effect would be quite the opposite. Sorry if this was asked already, but have identified whether it's CPU _FAN or CPU_OPT where this happens?

When I'm using the fan hub, it doesn't matter what header I plug into, one of the 4 fans will run at 100% (makes me think it's running like it's a 3-pin fan, and not a PWM fan?). When I'm plugged directly into both CPU and CPU_OPT the same behavior occurs, which leads me to think it's some kind of limitation on my motherboard, since everything plays nice when I've got two fans in CPU and two fans in a system header.