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Started by noblephantazm | | 5 answers
Old 12 Volt Cpu fan rewired to a casefan running at fullspeed.
I took my old cpu fan 4 wired and rewired it into a 2 wire power supply wire to be a case fan and its constantly running at full speed.

The question is, is it safe for it to leave it spinning at full speed? and if not how can i control it.

Also you have to push start the fan to power it up.
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a c 86 ) Power supply
a c 144 à CPUs
October 17, 2014 12:27:24 PM

Thanks.

Since everyone seems to have a color code. Intel seems to go

Black = common / negative
Yellow = 12 volts.
Green = Sense(RPM)
Blue = PWM

As long as you connected black to black and yellow to yellow(12 volts). Some fan adapters may use red in place of yellow as it was the default fan color for almost all 3 pin fans.

You can actually just use a 3 pin fan to molex as well. The PWM pin can hang safely over with edge without any issues. PWM fans will run full speed when no PWM signal is detected. I have gone as far as to cut shrouded 3 pin adapters to connect 4 pin fans.
October 17, 2014 10:42:53 AM

nukemaster said:
Can you tell us exactly what the old wires had been. The push start thing is strange. almost sounds like you have it on 5 volts or something.

Running fans full speed do not hurt them as it is part of the design.

4 pin fans that are PWM can be controlled via a signal on the 4th wire. 3 and 2 pin fans are controlled by voltage. so running a 12 volt fan on 7 volts will slow it down and make it more quiet.

Slowing down a fan can extend its life, but running them full speed is not actually going to hurt it.


it was a former cpu fan, and has green,blue,yellow and black wires.
a c 156 ) Power supply
a c 376 à CPUs
October 17, 2014 10:38:15 AM

12v fans will always run at full rpm when directly wired. That is their normal mode of operation.
If you want, there are low noise fan wire adapters or you can use a zalman fanmate which will reduce the voltage and slow down the fan.
If noise is not an issue, I would not bother controlling it.
a c 86 ) Power supply
a c 144 à CPUs
October 17, 2014 10:31:16 AM

Can you tell us exactly what the old wires had been. The push start thing is strange. almost sounds like you have it on 5 volts or something.

Running fans full speed do not hurt them as it is part of the design.

4 pin fans that are PWM can be controlled via a signal on the 4th wire. 3 and 2 pin fans are controlled by voltage. so running a 12 volt fan on 7 volts will slow it down and make it more quiet.

Slowing down a fan can extend its life, but running them full speed is not actually going to hurt it.

Best solution chosen by noblephantazm

October 17, 2014 10:28:08 AM

If the fan has a 3 pin connector, itl run at one constant speed but most newer fans have 4 pins (4th pin is for controlling the fan speed). Should be fine considering a fan is a fan.

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