Noctua NF-A12x25 going at 3000+ RPM

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Opus131

Limp Gawd
Joined
Jul 29, 2016
Messages
298
The max fan speed should be 1900 RPM according to the box. Yet, at full speed it goes all the way up to 3200 RPM, where it stops, then goes back to max, stops and so forth. It remains steady at any speed short of the absolute maximum.

CPU is in idle and the fan is going at 1800 RPM right now. I used the auto tune utility from the motherboard software, an MSI B450 Pro Carbon Ac. Fan is plugged on the CPU header, four pins.

What am i doing wrong? I tried switching from auto to PWM in the bios but nothing. I can set the fans to the rate speed manually but i'm still concerned as it shouldn't do this, right? I also hope i didn't damage the fan by letting run at that speed.
 
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Nevermind i figured it out. I have the 5v version of the fan. No idea i had to look for that. Can't return it either. Damn.
 
Opus131 said:
Nevermind i figured it out. I have the 5v version of the fan. No idea i had to look for that. Can't return it either. Damn.
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well you could just hook it up to 5v all the time (if the noise at normal speed is ok, which it should be)
 
If i set PWM to make it go at the rated speed, would that supply the right voltage?

I don't think i have anything in my motherboard that can output 5v. Do i?
 
Opus131 said:
If i set PWM to make it go at the rated speed, would that supply the right voltage?

I don't think i have anything in my motherboard that can output 5v. Do i?
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all power supply's have red 5 volts rails on most of the hook ups....if you have the all black wires id have to look up which molex pins are the 5v...nm here ya go

IM sure they make adapters on sale on ebay or make your own in a pinch
Screenshot 2021-06-26 130203.png
 
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Opus131 said:
If i set PWM to make it go at the rated speed, would that supply the right voltage?

I don't think i have anything in my motherboard that can output 5v. Do i?
Click to expand...
No with PWM the fan always gets a constant voltage, it just pulses the signal.
 
Way way back in my noob days i bought several Delta 100cfm fans for my case to max out airflow. I swapped them all to the 5volt rails after hearing that jet engine sound for 5 min. At 5 volts they were tolerable Sorta
 
Opus131 said:
Nevermind i figured it out. I have the 5v version of the fan. No idea i had to look for that. Can't return it either. Damn.
Click to expand...
LOL
Was first thing I thought when I read tread title.
Nice to know I'm not the only one who sometimes pulls this kind of stunt. :D
 
doyll said:
LOL
Was first thing I thought when I read tread title.
Nice to know I'm not the only one who sometimes pulls this kind of stunt. :D
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its really a NONproblem....hook it up to a free molex 5 volt and call it done. Noctua are known to be quite at full speed anyways. All that reeving up and down is NOT necessary IMO on cpu fan
 
Many (myself included) use case and cooler fans that idle at 5-600rpm when system idles, speed up as load increase to 900-1100rpm under normal heavy load at about 65c in 21-23c ambient temp, but in hot weather (36-28c) with very heavy loads like rendering graphics fans spin on up to 1300-1500rpm to keep CPU below 75c. Hope that makes sense.
 
I for one am impressed it didn't crap itself!
Also another source of 5V is the USB and there are adapters for this (including Noctua's own).
 
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