Fan wire splice (risky?)

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freeman45

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Dec 26, 2015
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I found a 120mm fan in my junk-drawer and want to use it. But the 3 pin connector was torn off and long gone.
So I grabbed a pin from a smaller fan and spliced it to my big fan.

Red with Red
Black with Black
And yellow with blue.


I'm guessing the blue wire is for controlling the fan speed or monitoring the RPM's ?
Is this going to work, or is my computer going to self-destruct when I plug it in?
Any dangers what so ever?



syZM7ag.jpg
 
the blue wire reports RPM to the motherboard. It's a pretty safe assumption that the red and black are for negative and positive power and blue/yellow is fan speed; try hooking up the red and black wires to a 9v battery first to see if hte fan spins the correct way.

Most modern power supplies will shut off instantly if they detect a short. If you're really concerned find a molex to 3 pin fan connector, connect it to a power supply and google instructions on how to start a PSU without a motherboard.
 
I plugged it in a power adaptor and it spins. Not sure if it spins the right way though.
 
freeman45 said:
I plugged it in a power adaptor and it spins. Not sure if it spins the right way though.
Click to expand...

There should be markings on the fan case as to which way it's supposed to spin. PC fans almost always blow towards the back. The back being the side shown on your picture
 
as noted above the blue wire is just the tach

the black wire should connect to the edge of the plug and the red wire in the middle
 
With the price of fans and how readily available they are, just get a new one for piece of mind. Use this one for some other kind of project.

This may come in handy though...
From the 4-Wire PWM Controlled Fans Specification...
pwm_pinout.gif
 
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