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Case Fan question..

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Last response: in Systems
May 30, 2009 10:57:57 PM

Im putting together a new system, and I got 3 extra 120mm fans for my Antec 300.

They come with a wire with a small 3 pin that connects to the mobo, and an adapter to connect to a larger 4 pin power adapter. Now I guess without the small one connected to the mobo I cant get a fan reading, but my question is, if I just plug that small adapter into the mobo will that power the fan?

My old fans had both, one to plug into the mobo and another 4 pin for power.

More about : case fan question

a b B Homebuilt system
May 30, 2009 11:20:07 PM

May 31, 2009 7:20:50 AM

The 4th pin is so that you can control the fan speed from your BIOS or through software , so you might see some fan pins on your MOBO that have a 4th pin. you need the 1st 3 for power though or you get nothing.
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May 31, 2009 2:44:51 PM

Gin Fushicho said:
The 4th pin is so that you can control the fan speed from your BIOS or through software , so you might see some fan pins on your MOBO that have a 4th pin. you need the 1st 3 for power though or you get nothing.

I think we are talking about two different things. Im talking about one small connector that has 3 pins, and one large one that has 4 (like an IDE power port)
May 31, 2009 3:12:48 PM

Yeah , pin number 4 on the 4 pin connectors , We are talking about fans right? 4 Pins means your fan is capable of being controlled in the BIOS or by software but you have to attach it to a 4 pin connector if you want the controll otherwise just put it in a normal 3 pin connector , it will still work you just wont have the control. and in case I'm wrong a then what do you mean by its like an IDE power port?
a c 121 B Homebuilt system
May 31, 2009 10:01:55 PM

The Antec fans have molex connectors designed to plug directly into the PSU. The BIOS obviously cannot monitor those.

The small connectors come with either 3 or 4 pins. The are designed to plug into the motherboard. The BIOS can monitor a 3 pin fan and can control a 4 pin fan.
June 1, 2009 1:14:14 AM

Well , at elast you can understand what he was asking.
a b B Homebuilt system
June 1, 2009 3:29:59 PM

OP, you have it right, basically. It appears your fans have two options. One is the larger 4-pin connector, which I assume is the Molex connector usually used to power a hard drive, etc. It comes directly from the PSU and you are right, that way provides no means to control the fan by the mobo. Moreover, that way the mobo has no way to monitor the fan operation, so it cannot alarm you if the fan quits. By the way, if you do this and end up with no fan connected to a mobo Case Fan connector, you should set the BIOS to ignore the (non-existent) fan speed signal on this unused connector.

The smaller 3-pin plug is the way to go because it allows the BIOS to do the whole job. In those wires and the matching mobo connector, one lead is the + dc supply to run the fan, one is the fan speed signal going back to the mobo, and one is the (shared) ground. This allows the BIOS to monitor fan speed AND control it if you wish. It simply controls the + dc supply to the fan - no fourth lead needed. At least, that's how my mobo works. Newer mobo's with 4-pin fan connectors, I'm not so sure about, but I'm guessing they are simply supplying a separate "Ground" lead for the fan speed signal. In that case, read you mobo manual carefully to determine whether it really will control the fan speed if only 3 pins are used.

Doing this with multiple fans can get tricky. I don't know what your mobo has, but most have at least a CPU Fan (obviously to be used only for the CPU heatsink fan) and one or two Case Fan connectors. Many now also have a PSU Fan connector for use IF your PSU has a matching 3-pin lead. If you have only two case fans, it's relatively simple to hook them up, although sometimes only one of the mobo sockets will be used for BIOS-controlled fan speed. But if you have more case fans than connectors it gets trickier.

You could modify the case fan wiring to connect two fans in parallel, but note two things for this. One is that you cannot connect together the two fan speed sensor leads. Basically you would leave only one of those leads connected to the mobo, and not connect the other at all, leaving its fan speed unmonitored. But you do connect the ground and + dc supply leads in parallel so both fans run with the same dc supply under BIOS control - control is usually based on some case temperature sensor. The thing to check, if you can, is to be sure the power available at the mobo connector is sufficient to run two fans in parallel. That is, each fan cannot use more than half of the current available to fans on this connector.

Some mobo's have 4-pin connectors on them for fans because there are some fans made that way. If your mobo is like this, check the documentation on how to plug in a 3-pin fan lead.

One way to handle more case fans than mobo sockets is to hook up to the mobo connectors as many as they will accomodate, then connect the additional case fans directly to the PSU via the 4-pin Molex. That way the direct-connected fans run always at full speed, and the mobo-connected fans can be controlled by the BIOS to augment them with whatever additional cooling is needed.
June 7, 2009 10:51:36 AM

Hi, :hello: 

I'm preparing for a new build for gaming, I want to keep my 7 year old Addtronics 6820A Full Size Case. It has (2) 80mm Front/(1) 80mm Side Door & (1) 120mm Rear "out".

I'm looking at moding the door fan making it a 120mm or should I go larger ???

I see 80mm fans for $1.99 Masscool & fans for $17.99 with many different options.

Please recommend a "Good" fan I can buy, it does not have to be the be$t:

MASSCOOL FD08025B1M3/4 Case Fan - Retail $2.59
2700±10% RPM 32.95 cfm a...

GELID Solutions FN-FW08-20 80mm Gamer Fan WING 8 Green - Retail $17.99
Compatibility: Case
Bearing Type: Nanoflux Bearing (NFB)
RPM: 2000 RPM
Air Flow: 28.1 CFM
Noise Level: 21 dBA
Power Connector: 3 Pin Molex
Dimensions: 80 x 80 x 25mm
Features: Nanoflux Bearing (NFB) Optimized Winglet Fan Blades Waterproof & Dustproof Long Lifetime (100'000 h MTTF at 40°C) Silicone Fan Mounts Fan Speed Control Safety Approvals: UL, CUL, CE, RoHS Compliant
Model #: FN-FW08-20
Item #: N82E16835426012

Case looks like this one:

DIMENSIONS: 17.51"Dx8.27"Wx21.26"H