Question strange question about fan wiring: why is a PWM fan splitter wired the way it is? and is what I have done a problem?

[RAIDGoblin]

not sure if I was meant to post this one in cooling or components?

yesterday I got my soldering iron out to shorten some fan cables, to fix the bits of my cable management disaster that is in my power to fix, and I got a bit carried away. I have two case fans that are screwed together and powered off a PWM splitter and I decided in the moment to just solder them together to do away with the spliter entirely

I just joined all the wires together so both the fans are in parallel, I left a plug on both ends in-case I ever want to route the power the other way since everything is sleeved in position

I tested it off an old PSU to make sure I didn't blow anything up, then wired it in and it works fine, the BIOS appears to recognise it as one system fan, I don't know what it did before because I never looked

then I looked at the pinout on the noctua PWM splitter I had these on before, and only one of it's outputs have the 4 pins of PWM and the other only has 3, but what gets me is they're not the same three that a 3 pin fan has, it just seems weird and I don't get why it'd done that way. Should I have done mine like this?

now I'm worried it'll cause me problems that I have done it wrong, but that sleeving took hours so I don't really want to cut it all off and start again, I mean it works so I'm probably overthinking this, but if anyone knows why fan splitters are wired like this could you put my mind at rest LOL

thx for any help

 

[Eximo]

Conceivably with PWM fans you only really need 3 wires. Power, Ground, and Signal. RPM is optional.

3-pin fans is Power, Ground, and RPM.

Splitter may have only wired one of the fans for RPM? Would save a little bit at volume.

If they work with the header in PWM mode, that is fine. If they work in voltage mode and you are happy, no reason to change anything.

Fan headers don't detect multiple fans.

 

[dwd999]

The one pin that is not wired in a splitter is the tachometer which reports the fan speed to the motherboard, bios, etc. So only the speed of one of the fans is reported.

 

[RAIDGoblin]

Conceivably with PWM fans you only really need 3 wires. Power, Ground, and Signal. RPM is optional.

3-pin fans is Power, Ground, and RPM.

Splitter may have only wired one of the fans for RPM? Would save a little bit at volume.

If they work with the header in PWM mode, that is fine. If they work in voltage mode and you are happy, no reason to change anything.

Fan headers don't detect multiple fans.

ahhh, ok, this makes a lot of sense, thank you now I don't need to worry about it blowing up or causing damage or something, maybe the spliter is wired like that because it would mess things up if you plugged in two miss-matched fans?

 

[Glenwing]

ahhh, ok, this makes a lot of sense, thank you now I don't need to worry about it blowing up or causing damage or something, maybe the spliter is wired like that because it would mess things up if you plugged in two miss-matched fans?

If you have two fans with their speed sensors connected together, they will conflict with each other. That wire cannot be shared between fans.

 

[dwd999]

I guess you'll let us know if they conflict or double to report the total of both or just the highest one or something else. Or you could just snip off one wire.

 

[RAIDGoblin]

I guess you'll let us know if they conflict or double to report the total of both or just the highest one or something else. Or you could just snip off one wire.

like I say, the bios just seems to recognize it as one fan, but I don't have a way to measure the fan rpm so I have no idea if it's feeding back correct information or not? but it looks/sounds like it's spinning at the same speed it was before

I could cut one wire, that is true, thanks for the idea

 

[dwd999]

If you want you could use a free 3rd party program to monitor and control your fans:

Fan Control - A highly focused fan controlling software for Windows

Fan Control is a free software that allows the user to control their CPU, GPU and case fans using temperatures.

getfancontrol.com

 

[RAIDGoblin]

If you want you could use a free 3rd party program to monitor and control your fans:

Fan Control - A highly focused fan controlling software for Windows

Fan Control is a free software that allows the user to control their CPU, GPU and case fans using temperatures.

getfancontrol.com

thx for the recommendation, but I'm a debian user so I can't use that, I just set up fan curves in BIOS and leave it at that, I think there are programs I could use but I've never really looked into it