Fan Mod?

B

baballin328

Limp Gawd
Joined
Sep 7, 2006
Messages
437
I want to quiet down my fans. They're three pin but I have three pin --> molex converters. I've searched around on how to do a fan mod, but I still don't really get it. Can someone explain to me how to do this mod?
 
To convert a fan to 7v...

Take the positive (red) fan lead and attach it to the YELLOW (12v+) line on the molex.

Take the Negative (black) fan lead and attach it to the RED (5v+) line on the molex.


For 5v

Take the postive (red) fan lead and attach it to the Red (5v+) line on the molex)

Take the negative (black) fan lead and attach it to the black (ground) line closest to the red line on the molex.
 
can you do it to a 3pin fan header? Cuz my 3 pin to molex is different than the usual ones.
EDIT: NVM I figured it out, and it work wonderfully, it's much quieter in here now.... :D
 
baballin328 said:
can you do it to a 3pin fan header? Cuz my 3 pin to molex is different than the usual ones.
Click to expand...

no you can't do it to the fan headers on the motherboard since there's no 5v line to be able to use.

Your best bet would be to get a male to female molex molex extension cable, and then swap the 5v with the ground next to the 12v. Then connect your fans on molex adapters to the crossover extension cable.

Also, I can't remember my physics e+m to be able to understand how the 7v mod affects the 5v rail. Could someone chime in? I know the potential would be 7v, and the load off the 12v still, but how does the load work out for the 5v rail? I remember using a 450w ttgi psu and having the psu overload and switch off after having more than 2 fans at 7v. Then again, nothing was loading the psu except for the fans, so that could be why (since you're not supposed to just load a single rail). I never tried it on my psu when I had everything else running.
 
Actually I did it with the 3 pin fan. You just have to take out the pins and then plug it in like in the molex fan mod and it seems to be working fine...
 
baballin328 said:
Actually I did it with the 3 pin fan. You just have to take out the pins and then plug it in like in the molex fan mod and it seems to be working fine...
Click to expand...

Oh you meant you modified the 3pin-molex adapter? That works too if you could pull and swap pinout. I thought you mean plugging 3pin into the motherboard and running 7v. Glad you got it working :)
 
No I didn't modify the 3 pin molex converter. I modified the 3 pin itself. You take the blank and red pins out of it and you can plug it into a molex plug from the powersupply. But nothing is plugged into the motherboard
 
baballin328 said:
I want to quiet down my fans. They're three pin but I have three pin --> molex converters. I've searched around on how to do a fan mod, but I still don't really get it. Can someone explain to me how to do this mod?
Click to expand...

To convert a typical 12V fan to 5.5V solder a 68 ohm resistor in series with the red 12 wire of the fan itself. Never mind monkeying around with power leads and splicing wires..

That's all there is to it. And that is the safe and easy way to do it. Splicing wires between the 12V and 5V outputs of your power supply is unsafe and is more difficult. The resistor is completely safe, foolproof and you only have to cut 1 wire.
 
wdn said:
To convert a typical 12V fan to 5.5V solder a 68 ohm resistor in series with the red 12 wire of the fan itself. Never mind monkeying around with power leads and splicing wires..

That's all there is to it. And that is the safe and easy way to do it. Splicing wires between the 12V and 5V outputs of your power supply is unsafe and is more difficult. The resistor is completely safe, foolproof and you only have to cut 1 wire.
Click to expand...

Hows it unsafe or difficult lol... Soldering a resistor would seem to be more difficult than re-arranging some wires...
 
After you remove the black and red wires you are left with this:

The red and black wires look like this after you take them out:

and then you can just plug the two wires into a molex plug.
12V
_________
/( ) ( ) ( ) ( ) \
R B

7v
_________
/( ) ( ) ( ) ( ) \
R B

5V
_________
/( ) ( ) ( ) ( ) \
B R
 
Is it possible to take a 4pin molex and take it down to 3pin? I'd like to convert some of my 120mm fans to use mobo headers rather than molex.
 
Arcygenical said:
Hows it unsafe or difficult lol... Soldering a resistor would seem to be more difficult than re-arranging some wires...
Click to expand...

It is unsafe because are tapping the power supply across two points you are not supposed to tie together thats why. You are affecting the voltage of your 5V supply. I would never tie two different (+) voltage leads together and not going to ground. That is fairly insane. It is much safer to stick with the existing red 12V lead of the fan and drop it down buy soldering in a resistor. People who are interested in hardware mods should become comfortable with a soldering iron and develop some basic skills and confidence with one.

The other obvious advantage of soldering in a resistor is you can make the fan go precisely any speed you want it to go by calculating the proper R value.
 
wdn said:
It is unsafe because are tapping the power supply across two points you are not supposed to tie together thats why. You are affecting the voltage of your 5V supply. I would never tie two different (+) voltage leads together and not going to ground. That is fairly insane. It is much safer to stick with the existing 12V lead of the fan and drop it down buy soldering in a resistor. People who are don't know how to use a soldering iron should generally avoid hardware mods altogether.

The other obvious advantage of soldering in a resistor is you can make the fan go any speed you want it to go by calculating the proper R value.
Click to expand...

Well technically correct, people have been doing this for years, and power supplies are quite robust in this area...

I'd never do it outside of a computer, or inside a server or something...
 
wdn said:
It is unsafe because are tapping the power supply across two points you are not supposed to tie together thats why. You are affecting the voltage of your 5V supply. I would never tie two different (+) voltage leads together and not going to ground. That is fairly insane. It is much safer to stick with the existing red 12V lead of the fan and drop it down buy soldering in a resistor. People who are interested in hardware mods should become comfortable with a soldering iron and develop some basic skills and confidence with one.

The other obvious advantage of soldering in a resistor is you can make the fan go precisely any speed you want it to go by calculating the proper R value.
Click to expand...

Correct me if I'm wrong, but isn't it only messing with different rails if you do the 7v trick? It is my understanding that the pins in a molex connector are +5,-5,-12,+12. My two 120mm fans are currently wired in parallel circuits to a switch on the front of my case so that I can switch between 12v and 5v at will. I get near-silent at 5v, but the increased airflow of full 12v speeds if I need it. The 7v trick, however, did seem pretty dangerous to me... or at least not a great idea.
 
A Shiny Demon said:
Correct me if I'm wrong, but isn't it only messing with different rails if you do the 7v trick? It is my understanding that the pins in a molex connector are +5,-5,-12,+12. My two 120mm fans are currently wired in parallel circuits to a switch on the front of my case so that I can switch between 12v and 5v at will. I get near-silent at 5v, but the increased airflow of full 12v speeds if I need it. The 7v trick, however, did seem pretty dangerous to me... or at least not a great idea.
Click to expand...

The molex pins are +5v, Gnd, Gnd, +12v. because both the +5 and +12 volt lines are referenced to the same Gnd point the 7 volt fan mod works fine. The end result of the mod (what the power supply sees) is current is pulled from the 12V line and pushed into the 5v line. The only way this could cause a problem in the power supply is if you drew more current from the 12 v line than the rest of the 5 volt draws are. then voltages would fly around.
 
A Shiny Demon said:
Correct me if I'm wrong, but isn't it only messing with different rails if you do the 7v trick? It is my understanding that the pins in a molex connector are +5,-5,-12,+12. My two 120mm fans are currently wired in parallel circuits to a switch on the front of my case so that I can switch between 12v and 5v at will. I get near-silent at 5v, but the increased airflow of full 12v speeds if I need it. The 7v trick, however, did seem pretty dangerous to me... or at least not a great idea.
Click to expand...

Yes to be more precise, the 5V mod is safe because it is not really a mod as I think of it, it is tapping the +5V on one side and ground on the other. That is safe.

The 7V mod however is unsafe and its bad practice. You are tying together a +5V and 12V lead -- no ground -- and relying on the fact that the drop in potential between these to (+) terminals equates to 7V.
 
[BRO]Alaskan;1030511095 said:
The molex pins are +5v, Gnd, Gnd, +12v. because both the +5 and +12 volt lines are referenced to the same Gnd point the 7 volt fan mod works fine. The end result of the mod (what the power supply sees) is current is pulled from the 12V line and pushed into the 5v line. The only way this could cause a problem in the power supply is if you drew more current from the 12 v line than the rest of the 5 volt draws are. then voltages would fly around.
Click to expand...

Ah, that makes complete sense as to why when I was using only the 12v rail on a psu to try 7v, it overloaded after 2 fans. Makes me feel safer running them at 7v in my full setup now.

wdn said:
Reminds me of the Big Dig ... what could possibly go wrong? :p
Click to expand...

haha you're from massachusetts too?
 
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