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Weird stuff going on with my cooling - Page 2

post #11 of 16
Thread Starter 
Hmm in confused. Doesnt a fan need pwm (3pin) to control it? Whats the 4th pin then?
post #12 of 16
3pin = voltage regulation
4pin = PWM (pulse width modulation)

in 3pin, the voltage is adjusted to vary the speed of the fan
in 4pin, the fan always run @ 12v but is turned on and off really quickly to vary the speed of the fan. (the 4th pin is the signaling to turn the fan on and off)

if you plug a 3 pin fan into a 4 pin header, it will run at full blast because the speed control on a 4 pin(PWM) header is the 4th pin that's supplying the PWM signal. also, not all mobo fan headers can be controlled. some headers just run full blast. so that may be your problem.
post #13 of 16
Quote:
Originally Posted by mikupoiss View Post

Quote:
Originally Posted by EPiiKK View Post

Okay, i think i solved this.
The 3 pin motherboard fan headers are not PWM? I put both of the fans to 4 pin headers, even tho the fans are 3 pin, and now i can control them fully. i thought the 3 pin headers were pwm too.

When i get my new case i'm gonna use spliters to put all my fans to the motherboard 4 pins! thumb.gif

I haven't seen a single 3-pin PWM. Can it even be made with the PWM spec? They all have 4 pins, so putting 4-pin fan onto 3-pin header doesn't report speed signal and is permapowered for high speed. Or something like that .P
No, 3-pin headers are not PWM. Some have no speed control at all.
4-pin headers are not all PWM either. Usually the only PWM headers on a motherboard are the CPU fan & CPU opt. 4-pin headers.

3-pin header pinout is Gnd, 12V, RPM signal. If header has speed control the 12V is variable voltage.

4-pin PWM header is Gnd, 12V, RPM signal, PWM signal. The PWM signal goes to PCB in fan that pulses the 12v powr to fan.

4-pin non-PWM header is Gnd, 12v, RPM. Reserved.

Some 4-pin headers can be both PWM or voltage control. Sometimes this has to be set in Bios, sometimes it's automatic.
Edited by doyll - 3/16/14 at 4:31pm
post #14 of 16
Thread Starter 
Quote:
Originally Posted by doyll View Post

No, 3-pin headers are not PWM. Some have no speed control at all.
4-pin headers are not all PWM either. Usually the only PWM headers on a motherboard are the CPU fan & CPU opt. 4-pin headers.

3-pin header pinout is Gnd, 12V, RPM signal. If header has speed control the 12V is variable voltage.

4-pin PWM header is Gnd, 12V, RPM signal, PWM signal. The PWM signal goes to PCB in fan that pulses the 12v powr to fan.

4-pin non-PWM header is Gnd, 12v, RPM. Reserved.

Some 4-pin headers can be both PWM or voltage control. Sometimes this has to be set in Bios, sometimes it's automatic.

Thanks for clearing this up! So is there any benefits from running 4pin pwm compared to voltage controlled fans?
post #15 of 16
PWM fan usually idle at lower speed. Instead of only a few different speeds (5v, 7v, 10v, 12v) on voltage speed the speed can adjusts to almost any rpm, can run 6-8 fans on one PWM header using PWM splitter / hub with PSU power meaning automatic speed control can be used on all fans in a system as long as they are PWM. Links in my sig explain how to do it.
post #16 of 16
Thread Starter 
Quote:
Originally Posted by doyll View Post

PWM fan usually idle at lower speed. Instead of only a few different speeds (5v, 7v, 10v, 12v) on voltage speed the speed can adjusts to almost any rpm, can run 6-8 fans on one PWM header using PWM splitter / hub with PSU power meaning automatic speed control can be used on all fans in a system as long as they are PWM. Links in my sig explain how to do it.
Very helpfull, thanks! thumb.gif
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