Need help wiring some fans

So I need to wire up the CPU fans from a Powermac G5 to fit in a standard motherboard fan header.

The CPU fans have an odd 8 pin block connector like this:

These power both of the fans.

I found some basic wiring diagrams from:

The one for the CPU fan looks like this:

Basically I need to wire this up so that both fans can be powered from 5VDC on regular 3/4 - pin fan headers.

P.S. I have checked the current draw for all the fans I will be running, it is below 1A so don't worry.

Thanks in advance

Well I do not know why those fans get +12V and +5V; I would check if the pin 4 (+5V) is realy needed.

I would assume, that hooking up +12V, neutral and tacho (RPM) would be enough.

Test if the fans spin up if you connect +12V and GND (neutral) .. if that works you can forget about the +5V;

Thats how normal fan headers are wired:

The 4th pin on 4 pin headers is a PWM (pulse with modulation) signal, which allows changing the fan speed without the need to lower the voltage on the +Vcc line.

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OK now that I have time to actually work on this:

Seeing as there are two 12V connectors (one for each fan), how should i wire them into the 3 pin fan connector? Or should I just try wiring the 5VDC for both fans into the 12VDC on the fan connector?

It's likely that the reason it has both 12 and 5 volt is so the fan can be run at either voltage. So you should be able to ignore the 5v completely. Just wire both 12v wires together in to the header. With the RPM wires just connect one and ignore the other, I don't think it works if you have both connected.

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Thanks. I'll give this a try and report back.

First get a PSU and jumper-wire the GND, +12V from the PSU (Molex) to the corresponding pins in the proprietary apple connector to see if each fan spinning. If it does not, add another jumper from the +5V of the molex to the +5V pin on the proprietary apple connector and see if it spins.

If the fans span when you apply +12V to the +12V pins (for each fan on its own for testing) than you can go ahead and connect the +12V pin of the fan to the +5V from the molex and see if it still spins. If so you can wire the +12V, GND and tacho of the fans onto the 3pin fan connector.

Either each fan on its own, or both onto one (than its like a Y-splitter cable)

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The molex harness on this PSU that I have has a 4 pin (female) connector on the end. Can I use this to jump the fans? It would be easier to just stick a paperclip in each end of these female connectors than have to make it fit in the standard molex connector.

It looks like this:

Usually on a mole plug the yellow is +12V the red one is +5V and both black ones are GND.

This connector is the legacy of the floppy drive; but still the pinout is the same.

Cool thanks, I shall report back.

Dont you have any somewhat insulated wire? - I mean you have a bad history of shorting stuff :P

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I have plenty of electrical tape, dont worry. XD

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@Th3Z0ne @Dexter_Kane

After connecting
12V Fan A -----> +12V Molex
GND-------------> GND Molex
5V Both Fans--> +5V Molex

One of the fans spins. I assume you have to wire: 12V fan A, 12V fan B and 5V Both fans to the +12VDC on the fan connector for them to both power on.

Try it without the 5v, just have both 12v wires and the ground wire connected to the molex connector.

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With that setup neither of the fans spin. Gonna try with +5V as well now

@Dexter_Kane @Th3Z0ne

Success, With the 12V for both fans and the 5V connected, both of the fans spin.

Is it safe to wire all three connections onto the +12VDC of the 3 pin fan connector?

Doubt it. I'm not sure what that 5V is for but I wouldn't connect it to 12v. Either it won't work because it's using it to get 7v to run the fans, or something will catch fire.

Right, Is there any way of wiring it to a molex connector but stepping down the voltage? (they are quite loud at full speed).

Also would it be safe with 1 fan rather than both?

In case this helps the fans are rated:

DC12V 0.63A


Would it be possible to wire the 12V fan A and 12V fan B to the 3 pin connector and then wire the 5V both fans to the molex 5V? This way the molex just provides supplementary power and the fans should be able to be controlled from the motherboard?