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Control two different fans with one fan header w/ Y splitter

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  • Cases
  • Fan
  • Motherboards
  • Corsair
Last response: in Motherboards
July 3, 2014 4:53:03 PM

So I'm upgrading the stock fans on my 350D Corsair case. I'll be using two AF140 in the front, another AF140 on top and a AF120 in the back. Unfortunately my Asus h87m-plus only has two headers so I was thinking about using two splitters and connect the front fans to one header and the back/top fans to the other header. I know the headers can handle the increased current but what about pairing the 120 and the 140 on the same header?

My guess is that since the fans are voltage-controlled there should not be any problems and they would go full speed (one at 1100 and the other at 1600 RPM) when using 12V with the header supplying 0.1A to one and 0.35A to the other. My doubt is if all that is true, specially the current delivery to each fan.

BTW, I know that I would only be able to read the speed of either the 120 or 140mm fan but that's not that big of a deal for me. And luckily the splitters I have already come with one of the speed reading pins removed

More about : control fans fan header splitter

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a c 174 V Motherboard
July 3, 2014 7:06:17 PM

Two fans on one header is not ideal but should be fine. If you are plugging them into a regular fan header which is voltage controlled, then both fans connected should run to the RPM appropriate for whatever the applied voltage is, as controlled by either the bios or software (Fan Xpert, Fan Speed, etc.). As you say, because they're different sizes and RPM specs, they're never going to run at the same speed, but that's largely irrelevant. As far as current delivery, each fan will draw what it needs to run - as long as the total doesn't exceed the header's rated capacity (normally 1A) you're golden.

I had a hard time figuring out what you were actually asking - hopefully I answered it to your satisfaction.
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July 4, 2014 8:49:37 AM

volcanoscout said:
Two fans on one header is not ideal but should be fine. If you are plugging them into a regular fan header which is voltage controlled, then both fans connected should run to the RPM appropriate for whatever the applied voltage is, as controlled by either the bios or software (Fan Xpert, Fan Speed, etc.). As you say, because they're different sizes and RPM specs, they're never going to run at the same speed, but that's largely irrelevant. As far as current delivery, each fan will draw what it needs to run - as long as the total doesn't exceed the header's rated capacity (normally 1A) you're golden.

I had a hard time figuring out what you were actually asking - hopefully I answered it to your satisfaction.


That was really helpful thank you. The fans arrived yesterday and I really liked their noise profile. When slow they really are silent and at full speed you hear just the air movement. The fan splitters will arrive tomorrow so then I will be able to test everything. As far as I know the headers are rated for 1A so that should be plenty to drive all the fans.

I'm really looking forward to have the final fan configuration. I love the 350D case but I feel the stock fans are simply not enough. I have an Asus GTX 780 DCII and it was reaching 80 degrees (which is not terrible) when running Heaven at overclocked speeds. After plugging both back and top fans (in the two headers, still no splitters) and leaving the front door opened, the highest I got was 68!! This is more in line with the temps I've seen in all the reviews. I hope I can even improve or at least keep this temperatures when installing the front fans and closing the door.
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a c 174 V Motherboard
July 4, 2014 8:10:57 PM

You should be good to go once your front fans are installed. After all, the case was designed to run with the front door closed. I know where you're coming from though- it took me a while before I was comfortable leaving the front door on my R4 closed, even after monitoring and comparing temps.
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July 5, 2014 7:29:25 PM

volcanoscout said:
You should be good to go once your front fans are installed. After all, the case was designed to run with the front door closed. I know where you're coming from though- it took me a while before I was comfortable leaving the front door on my R4 closed, even after monitoring and comparing temps.


Ok so i got the splitters and ran Heaven again, this time with all four fans running and the case's front door closed. I got a max of 72 degrees. It's incredible how bad case airflow can affect your temperatures, specially when you have a non reference gpu, which blows hot air into the case.
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a c 174 V Motherboard
July 5, 2014 8:41:17 PM

72 isn't bad...not great, but not bad. Should be much better though, considering the two fan addition. The 350D, as with most of the Corsairs that I've looked at, was designed with liquid cooling in mind, so airflow is kind of an after thought. I'm assuming you've got all your cables clear of the air path. How is your PSU oriented - fan up or down? What did you have your case fans set at?
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July 6, 2014 10:22:41 AM

volcanoscout said:
72 isn't bad...not great, but not bad. Should be much better though, considering the two fan addition. The 350D, as with most of the Corsairs that I've looked at, was designed with liquid cooling in mind, so airflow is kind of an after thought. I'm assuming you've got all your cables clear of the air path. How is your PSU oriented - fan up or down? What did you have your case fans set at?


I guess the orientation of all the fans are pretty standard. PSU with fan down, Back/Top exhaust fans and two intake front fans. Now I live in Florida and room temperature right now is probably around 28 degrees celcius so that is something to consider. Most reviews have room temps in the low 20s
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a c 174 V Motherboard
July 6, 2014 11:55:01 AM

That would explain it. Since I doubt dust is a big issue there, if you don't have any small children or animals, you could just leave the front panel off. I'll bet that would knock 6-8 degrees off the top, if you think you need it. Another option, depending on your PSU and how often the intake fan on it runs, is to flip it fan up and use it as a pseudo-exhaust fan. It will increase the temp of air inflow into the PSU, but again depending on the PSU, as the GPU exhaust temp rises and incidentally heats the PSU, the PSU fan should spin up in response and help suck the hot air out of the case and expel it out the rear. In practice, that doesn't work for me - my GPUs would have to be on fire before my PSU fan even started spinning.
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July 6, 2014 12:25:59 PM

volcanoscout said:
That would explain it. Since I doubt dust is a big issue there, if you don't have any small children or animals, you could just leave the front panel off. I'll bet that would knock 6-8 degrees off the top, if you think you need it. Another option, depending on your PSU and how often the intake fan on it runs, is to flip it fan up and use it as a pseudo-exhaust fan. It will increase the temp of air inflow into the PSU, but again depending on the PSU, as the GPU exhaust temp rises and incidentally heats the PSU, the PSU fan should spin up in response and help suck the hot air out of the case and expel it out the rear. In practice, that doesn't work for me - my GPUs would have to be on fire before my PSU fan even started spinning.


That's a good idea. I'm not really uncomfortable with the gpu temperature now so I think I'll leave everything as it is. I'll probably turn the air conditioner to cool the room and then test the temps again to see if I can get close to what the reviewers are getting.
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a c 174 V Motherboard
July 6, 2014 1:33:12 PM

Awesome - let me know how you make out!
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