3 pin fan into 2 pin slot

substance12

Senior member
Nov 6, 2000
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I have a 3 pin fan (red, black, orange) and my PS only has a 2 pin slot. so far I haven't been able to find the right combination to get it to work and so I've concluded that I probably need to connect all 3 for the fan to work. Can someone tell me how to get this fan to work?
 

Zepper

Elite Member
May 1, 2001
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Make and model and any other specs from the label on the fan you removed from the PSU?

Make and full model no. and any other specs from the label of the new fan?

Make and full model no. of PSU?

I've not seen a fan with an orange lead. Many have yellow for the speed sensor wire (I've also seen blue or white). Power wires are usually red and black. Red is +12 and black is ground. If you are using the same two pins inside the PSU, the fan might not work if it is not the same or very close to the same internal resistance as the fan that was removed because the thermal control circuit is matched to the power needs of that fan.

So if you wan't to use that fan, you may have to bring the fan lead outside the PSU case (may need an extension or two) and hook it to your fan controller or a header on the mobo.

.bh.
 

pkrush

Senior member
Dec 5, 2005
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I wouldn't run it from the PSU's fan connector, since if you do you're going to have two fan controllers wired to that fan (the one on the fan and the one on the power supply fan connector) and the fan won't even turn on until the power supply gets EXTREMELY hot.
 

Zepper

Elite Member
May 1, 2001
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That AC may not move enough air to keep the PSU cool. And yes, the AC takes only half the power of the globe so it has about twice the resistance - so it should work with that thermal controller (likely the TC won't slow it down much). You also need to remember that the fan won't run when the PSU is in standby mode as only the +5V standby rail is working - the PSU has to be fully powered on to test whether the fan works. IAC, the AC fan is low and slow so running it even full speed shouldn't be very noisy.

.bh.
 

Zepper

Elite Member
May 1, 2001
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Yes, I didn't notice that that AC fan was the TC model so it has to be wired directly to +12 at all times - no other controller in the circuit. So all you need to connect to the two pin header inside the PSU is the black wire. The red wire should be spliced directly to +12V (yellow wire from the PSU) or both wires directly to an uncontrolleed mobo fan header or a drive-bay type fan controller channel turned full up at all times. I do like to monitor the speed of my PSU fan, so if you have a monitored, uncontrolled fan header on your mobo, that would be best - just need a fan extension or two to reach it. Tape the extension connectors so they don't come apart accidentally. I almost let the "magik smoke" out of one of my PSUs due to a faulty extension contact. :eek: Luckily my nose was working better than my wiring at the time...

.bh.
 

cryptonomicon

Senior member
Oct 20, 2004
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The orange wire is just for monitoring. With some sharp scisors you can cut out that box then plug the other two in.
 

substance12

Senior member
Nov 6, 2000
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Originally posted by: cryptonomicon
The orange wire is just for monitoring. With some sharp scisors you can cut out that box then plug the other two in.

that's what I did at first and it wouldn't power on.