[SOLVED] Cant change fans RPM...

Sep 6, 2019
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Hello, i just recently added two noctua case fans to my pc, i have an Asrock motherboard and am using A-Tuning. A-Tuning recognizes my Chasis fan , and Chasis fan 2, but wont let me change Chasis fan 2's RPM. Chasis fan 2's cable was a 4 pin and was plugged into a 3 pin, this is probably the problem but how can i fix it? would buying a 4 pin to 3 pin adapter work?
 

Darkbreeze

Titan
Moderator
You can't control a four pin PWM fan on a three pin header. There is NO resolution for that problem. Connecting a four pin fan to a three pin header will always result in full speed operation. Chances are, that 3 pin header either requires a three pin DC controlled fan OR is not a variable control header.

What is the exact model of your motherboard?

What are the exact models of your Noctua fans?

If you have the other fan plugged into a four pin header and it is working correctly then getting a PWM fan cable splitter and connecting BOTH fans to that header would be the cheapest and simplest solution.

https://www.amazon.com/JBtek-Black-Sleeved-Splitter-Converter/dp/B01EF9OI0O/ref=sr_1_3?keywords=pwm+fan+splitter+cable&qid=1567824619&s=gateway&sr=8-3
 
Reactions: Karadjgne

Darkbreeze

Titan
Moderator
You can't control a four pin PWM fan on a three pin header. There is NO resolution for that problem. Connecting a four pin fan to a three pin header will always result in full speed operation. Chances are, that 3 pin header either requires a three pin DC controlled fan OR is not a variable control header.

What is the exact model of your motherboard?

What are the exact models of your Noctua fans?

If you have the other fan plugged into a four pin header and it is working correctly then getting a PWM fan cable splitter and connecting BOTH fans to that header would be the cheapest and simplest solution.

https://www.amazon.com/JBtek-Black-Sleeved-Splitter-Converter/dp/B01EF9OI0O/ref=sr_1_3?keywords=pwm+fan+splitter+cable&qid=1567824619&s=gateway&sr=8-3
 
Reactions: Karadjgne
Sep 6, 2019
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I have an Asrock B450M-HDV
The fans are Noctua NF-F12 PMW
Chasis fan 1 is plugged into a 4 pin an works just fine.
I couldnt find another 4 pin connecter on the motherboard but maybe im just blind.
 

Karadjgne

Titan
Herald
Pwm:
Ground, 12v+, tach, pwm signal
DC:
Ground, 5v+ to 12v+, tach

And that's the problem. There's no connection for the signal wire, so the fan does not know what speed to change to other than full speed since pwm are always 12v+.

Cheapest and best solution is to do as Darkbreeze suggested and a simple 2-way pwm splitter to the one header that does work the fan right, with 4 pins.
 
Sep 6, 2019
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Thanks for the help!
Sorry i may sound dumb, but does the splitter have two 4 pin ends that connect to another 4 pin? I could just plug the connector into the pins Chasis fan 1 is at and control both from it?
 

Karadjgne

Titan
Herald
Yep. On a 2-way splitter, there's 3 connectors. 1 goes to the header, the other 2 go to the 2 fans. The motherboard only 'sees' 1 connection, so believes it's only 1 fan, but powers/controls both simultaneously. It's not a perfect solution as you cannot control each fan seperately, both fans work the same at the same speeds according to just the 1 signal, but with the fans you have there's no other option. The only other viable choice would be to buy another fan, that's only 3pin DC not 4pin PWM, but it'd be a shame to park a Noctua on a shelf.
 

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