How to wire up a 4 wire Case fan

PhIlLy ChEeSe

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Apr 1, 2013
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Guys i want the most CFM out of my fans, there is no tutorials on "How To" that I can find. I'm hard wiring them in series to cool a rad, my Syth Caz fans are dying and I have replacements. Again just want to wire them up for the most cooling(or highest) speed.
I don't use fan headers, I hard wire so bare that in mind when give illustrations.................
 

Red Squirrel

No Lifer
May 24, 2003
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If you want maximum air flow you'll want to wire them up in parallel and not series. Are these 4 wire molex connectors? If yes the easiest is to just use splitter cables. If you don't have any or can't get any you can wire 12 volt to the yellow wire and 0 volt/negative to the black wire. If you're not sure which black you can do both, does not really matter.

If it's one of those mini connectors that has the RPM pin and PWM pin I think you can still wire them directly and not use those pins. I am not certain of the pin out though. I think it's still black and yellow, from a quick google search I did. If you leave the others I think the fan defaults to max speed.

As for physically connecting them, I've never really figured a clean way for that myself. I usually solder them together, add lot of hot glue, electrical tape, and tie wraps to keep electrical tape in place (it will unwrap over time). It's ugly, but it works. :p

Never experimented with it myself, but you may be able to control the fans with something like an arduino or 555 timer circuit. You could add a temp sensor and make the sensor alter the speed of the fan, if you wish.
 

BonzaiDuck

Lifer
Jun 30, 2004
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. . . Are these 4 wire molex connectors? If yes the easiest is to just use splitter cables. . . . .
. . .

If it's one of those mini connectors that has the RPM pin and PWM pin I think you can still wire them directly and not use those pins. I am not certain of the pin out though. I think it's still black and yellow, from a quick google search I did. If you leave the others I think the fan defaults to max speed.

. . . .
. . .

I woulda asked that. Splitters are the way to go, for either Molex or PWM-with-Molex.

If they're PWM fans, no sense in losing the PWM control just because you don't use the mobo ports and run Molex from PSU instead. Get the Swiftech splitter:

http://www.frozencpu.com/products/2...able_Splitter_-_SATA_Power_8W-PWM-SPL-ST.html

I think Akasa also makes one. The customer reviews suggest to me that the users don't know how to control their fans through BIOS and software, or they're nit-picky about full monitoring coverage. Since you only need the PWM pin of the CPU (or other) mobo port, you can run the yellow tach wires for additional fans to your mobo headers. If possibility you also need the ground wire -- I can't be sure. I'm pretty sure I once wired two 3-pin fans in parallel and used a second mobo port to monitor the extra fan, with only the spare tach wire connected -- nothing else. But you don't need to draw power from the mobo. Not with the Swiftech; probably not the Akasa. I've run more than a single fan from it, and it works fine.

For the 3-pin fans, yes -- you can wire the red and black in parallel. I've done it with four. But use only one fan's yellow tach wire and leave the spares out of the equation. Or try what I mentioned in the previous paragraph with available mobo ports.

I figure -- if you clean your case interior regularly, you can boot up and inspect fan operation before replacing the case side-panel. You don't have to monitor every fan, especially if you control them in groups of identical fan model.

Soldering skills: Primitive though mine are, I just taught myself. I strip a half-inch on each wire spread the thin wires of a cable in a sort of fan, tin them, and make a crude attempt to braid and then twist them together -- adding more solder last. I buy automotive self-adhesive rubber hose bandage. Electrical tape sucks. The self-adhesive stretchable rubber makes such a good insulation that you have the cut it off for removal.
 
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aigomorla

CPU, Cases&Cooling Mod PC Gaming Mod Elite Member
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Sep 28, 2005
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pwm_diagram.jpg


red wire (+)
Black whire (-)
Yellow Wire (RPM TAC)
(On some fans a Blue wire (PWM)


To wire to a molex:
images


Use Red Wire 12V+ -> Yellow Wire location on the molex head
Black wire on the GND next to 12V+ -> the black wire next to the yellow wire location.

That gives u max speed.

Do not use the 7V+ diagram in that chart, as a PSU was not intended to run that way.

If you want to use 5V+ use the GND next to the 5V+
 
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PhIlLy ChEeSe

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Apr 1, 2013
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Yeah I got some old fans that are dieing on me, so the bearing is binding now I guess. But there the 110CFM fans, as I don't mind noise but do like the best coolness. And yeah I split the cables extended them then hook them up as one.

Thanks all, not sure how I'm gonna wire them.
 

ehume

Golden Member
Nov 6, 2009
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You need to trot over to Wikipedia, do some homework. There is no need to reinvent the wheel. You only reinvent wheels when doing so is fun.

The commonest "110cfm" fan I know is the Scythe Slipstream 1900rpm fan. That's not PWM. That's 3-wire.

You can find lots of 3-wire and 4-wire cables floating around. Also cables with Molex connectors on the ends. All inexpensive. This guy is going out of business, so he is selling his stuff cheap; but all he has left are single braid cables, which tended to be extensive. You might find cheaper elsewhere.

Anyway, there is no need to kludge stuff together. no need; only do it if the doing itself is fun.
 
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BonzaiDuck

Lifer
Jun 30, 2004
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AigoMorla's post provides the big cap on the details.

If you had a spare mobo fan port for every fan, you could power every PWM fan through PSU->Molex and use that signal.

The Swiftech splitter uses the same signal from a single PWM mobo port to change the duty-cycle of every fan or pump connected to it -- equally. But the compromise means only one of these fans or pumps can be monitored through the tach wire. Unless -- you use a spare mobo fan-port's tach-pin.

At least, that' s my understanding of it.

I found some worthy PWM fans that are ~105 to 110 CFM. The Akasa Viper 140's -- the square model and the 140R -- are rated for that range and are fairly quiet. Then there's the line of Noctua iPPC fans. I'm using a 120mm unit rated at 3,000 RPM (really around 2,850) and 110CFM. Very quiet.

Of course, with that sort of air movement, you get the less-offensive noise component. The iPPC's are pricey, though.