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3 pin case fan into 4 pin mobo (fan speed)

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  • Cases
  • Fan
  • Motherboards
  • Fan Speed
Last response: in Motherboards
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March 21, 2014 12:36:58 PM

Hello, i just built a pc recently and found that my top case fan and top back fan is 3 pin and the one on my mobo is a 4 pin. Despite reading online that the last pin isn't needed and the fan will run top speed both fans seems to run sub standard at around 534 RPM standard and 620 RPM turbo. Im running both fans on one connector thru one 3 pin female to two 3 pin male adapter and runs the same without it. So what im asking is should i get a 4 pin to two 3 pin adapter? would it help? or is it just the connector itself bad?

The Specs:

Antec Twelve Hundred V3
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Asus Sabertooth Z87 mobo
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

More about : pin case fan pin mobo fan speed

a c 82 V Motherboard
March 21, 2014 12:39:14 PM

Have you tried ramping up the CPU to see if the fans speed up? I know with my mobo i can use 3 pin fans on the 4 pin headers and still have full speed control (just through voltage instead of PWM). They might be running slow because that's the profile it's set to.
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March 21, 2014 12:43:45 PM

No i haven't tried that yet, How would you do that exactly?
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a c 82 V Motherboard
March 21, 2014 12:47:53 PM

download prime 95 and run it for a few minutes, that, if anything, will run up your fans
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a c 283 V Motherboard
March 21, 2014 12:56:53 PM

Running both fans through one adapter is going to screw up the speed sensing unless you cut one of the wires.
If you connect just one fan does the rpm change?
Also, since speed is controlled by voltage, two fans on a single lead may getless voltage each and will have reduced speed

The Antec 900 has speed switches on the back, are they set to high rpm's?

If all else fails, buy a 3 pin to molex adapter and connect the fan directly to the psu.
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a b V Motherboard
March 21, 2014 12:57:02 PM

Hi

If you are not worried about noise from fans running at full speed you can get a molex to fan connector and run at 12v

Regards
Mike Barnes
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a b V Motherboard
March 21, 2014 1:00:02 PM

Fanum said:
Hello, i just built a pc recently and found that my top case fan and top back fan is 3 pin and the one on my mobo is a 4 pin. Despite reading online that the last pin isn't needed and the fan will run top speed both fans seems to run sub standard at around 534 RPM standard and 620 RPM turbo. Im running both fans on one connector thru one 3 pin female to two 3 pin male adapter and runs the same without it. So what im asking is should i get a 4 pin to two 3 pin adapter? would it help? or is it just the connector itself bad?

The Specs:

Antec Twelve Hundred V3
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Asus Sabertooth Z87 mobo
http://www.newegg.com/Product/Product.aspx?Item=N82E168...


On a true PWM header, the first two pins control voltage (constant, at 12v). The third pin reports back to the MB the RPM, and the fourth pin controls the PWM signal that controls the speed of a PWM fan. Putting a non PWM fan on one of these will in fact run at full speed at all times, since it is getting the full 12v (and doesn't understand the PWM signal telling it to slow down).
However, almost no motherboard case fan header is actually PWM, even if it has four pins. Typically, the CPU header is true PWM, and the rest are normal 3 pin fan headers, with a fake fourth pin that doesn't do anything and the speed controlled via voltage, on the first two pins. That is what is going on here; your motherboard is sending a variable voltage rate to the fans to control the speed.
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March 21, 2014 1:16:34 PM

Thank to everyone who answered i just tried the Prime 95 test and sure enough it got going when it needed to :) 
and thats what i was looking for.
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a c 82 V Motherboard
March 21, 2014 1:27:38 PM

Good to hear, it's nice when things work out :) 
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