3-2pin case/powersupply fan

thecoolnessrune

Diamond Member
Jun 8, 2005
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I need a question answered concering Power Supply fans. i bought 2 SOYO bundles a while back. One for me, and one for my uncle. Well, little benounced to me, it turns out that the power supply fan starts making a grinding sound about 3 months after purchase. I found the fan, removed it, and noticed it is sotered (spelling?) to the power supply. I can easily soter that without a problem. But the fan is 2 pin. I've heard of 3 and 4 pin but never 2 pin. Now I could be wrong but this is how I see it:

A 3 pin fan is composed of a positive, negative, and ground cable.

A 4 pin fan is composed of a positive, negative, ground, and variable speed controller cable.

My question is, can I simply cut the ground cable off of a 3 pin fan and use the other two??? Now I know what some of you are thinking: "A power supply is only $30, why the heck does he want to go through all this!" Cause I want to lol. So can anyone help me out here?
 

Ike0069

Diamond Member
Apr 28, 2003
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Actually a 3 pin fan is:
Power, ground, RPM monitoring

A 4 pin is:
12V, ground, ground,5V

So a 2 pin just lacks the RPM monitoring.

BTW: It's solder.
 

thecoolnessrune

Diamond Member
Jun 8, 2005
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Oh I see, so a 4 pin is just a more powerful fan that uses both 12V and 5V systems. So If I cut the RPM monitoring on a 3 pin fan (the cable other than red, yellow, blue, or black) will the fan still run? Since its just for a power supply it hasn't got to vary its RPMs. just run.
 

The Pentium Guy

Diamond Member
Jan 15, 2005
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Originally posted by: Ike0069
Actually a 3 pin fan is:
Power, ground, RPM monitoring

A 4 pin is:
12V, ground, ground,5V

So a 2 pin just lacks the RPM monitoring.

BTW: It's solder.

Since 2 of the pins go to ground anyway, is this what the molex "extra connector" is for?
On a fan you normally see a 4-pin molex female connector and a 4-pin molex male connector....

So does this mean that you can only use 1 molex connector (straight from the psu) for only 2 fans?
 

Operandi

Diamond Member
Oct 9, 1999
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Originally posted by: thecoolnessrune
Oh I see, so a 4 pin is just a more powerful fan that uses both 12V and 5V systems. So If I cut the RPM monitoring on a 3 pin fan (the cable other than red, yellow, blue, or black) will the fan still run? Since its just for a power supply it hasn't got to vary its RPMs. just run.

No all fans are 12v. All the "4 pin" fans just use two wires power and ground. 3 pin fans are the same except they the third wire is normally used for RPM output.

And yes you can use a 3 pin fan for your PSU, it will still control the fan's speeds but it doesn?t need the RPM output.
 

Zepper

Elite Member
May 1, 2001
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I would use a 3-pin fan and remove the two pins (red, black) from the 3-pin connector and connect the remaining wire (usually yellow) in the 3-pin connector directly to a mobo fan header so you can monitor the fan speed (use a 3-pin extension if necessary). Of all the fans in your PC, the ones that can cause the greatest damage if they fail are the CPU fan and the PSU fan. So those are the ones most needful of monitoring. I know! As I almost let the magic smoke out of one of my PSUs when messing around with the fan connections. Luckily my olfactory sense is in good working order... ;)
. Cut and splice the red/black fan power leads within the PSU - sometimes easier than soldering to the PCB. Or you could even use small wire nuts or crimp-type butt connectors.

.bh.
 

thecoolnessrune

Diamond Member
Jun 8, 2005
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I plan to. I am going to snip the old wires from the old fan and splice them to the new one using wire nuts. Everything should work properly. Thanks for your help people. If everything goes well, I'll tell you guys, If it doesn't, i'll be out $5 and so ticked off I won't write, lol.