Sign in with
Sign up | Sign in
Your question

Chassis Fans to MoBo

Last response: in Components
Share
August 12, 2011 11:23:47 AM

Hi guys, can you please give a little guidance on fan conns.

Mobo - ASUS P8P67
1off - 4pin CHA_fan1
1off - 3pin CHA_fan2
1off - 3pin PWR_fan1
1off - 3pin PWR_ fan2

Case - Coolmaster HAF X Nvidia Ed.
Fan - Front - 3Pin - red/black/white
Fan - Rear - 3pin - red/black/yellow
Fan - Side - 3pin - red/black/white
Fan - Top - 3pin - red/black/white
Fan - Internal - 3pin - red/black/ white - (Local to MoBo and PSU)

Can you advise me?
Are all yellow and white wires for speed control?
Which fans can plug into PWR and which into CHA?
Why do I have a 4pin MoBo fan connection?
How can I connect the 5 - 3pin fan conns into the available sockets.

Sorry to be so very basic with my questions, but the instruction leaflets that accompany the products are poor, and after trawling through the site forum I realise that lots of people attempting their first build have similar problems and they may also find your answers of great help.

As an aside: the case comes with a VGA bracket and I'm totally mystified as to what it's for and where it goes. Anybody else got this case and knows the answer? The booklet merely says 'Install VGA bracket or side air duct'. No reference anywhere to a side air duct!













More about : chassis fans mobo

a b ) Power supply
August 12, 2011 12:25:54 PM

Honestly you can plug the fans into whichever motherboard pin connection is available except for the CPU_FAN. Most fans comes with at least 3 pins; one pin/wire for positive, one pin/wire for negative, one pin/wire for speed control. I forget what the forth pin/wire is for at the moment but it won't affect your system if it's not plugged in.

It's your choice which of the four connections you want to plug into but people usually plug into the closest one for that specific fan so there isn't a jungle of wires everywhere. I would recommend connecting at least the front, rear and side fan. The last fan (either top or internal) can be connected if you find air flow is better with one or the other.
August 12, 2011 1:13:54 PM

Engima said:
Honestly you can plug the fans into whichever motherboard pin connection is available except for the CPU_FAN. Most fans comes with at least 3 pins; one pin/wire for positive, one pin/wire for negative, one pin/wire for speed control. I forget what the forth pin/wire is for at the moment but it won't affect your system if it's not plugged in.

It's your choice which of the four connections you want to plug into but people usually plug into the closest one for that specific fan so there isn't a jungle of wires everywhere. I would recommend connecting at least the front, rear and side fan. The last fan (either top or internal) can be connected if you find air flow is better with one or the other.



Thanks Enigma for your help.
Does this mean that I can't use the 4pin socket on the motherboard, or can I get a 4pin/3pin adapter. At the moment I'm 2off 3pin sockets short, and as I intend getting a powerful graphics card, I think I may need all 5off fans, and I'd prefer to connect them early in the build. This being so, can you suggest the best way of overcoming the shortfall.
I did read another useful contribution on the forum, suggesting that it is possible to splice up to 2off fans from 1off socket. If this is done, one should only use the Red/Black wires because, if the second speed control wire is spliced, then the computer will not know which fan to control. If this is the only option, then 2off of the fans will be running constantly at max rpm, and a decision would have to be made as to which fans are best suited in these conditions. It would be nice to get a 1x3pin to 2x3pin adapter but I don't know if the're marketted, even if they were I'd still have 2off fans running flat out.
Is it possible to adapt the situation so that all 5off fans can be run under variable speed control.


Related resources
a b ) Power supply
August 12, 2011 1:55:50 PM

You could also buy a separate fan controller that would mount into one of the 5.25" drive bays and control the fans manually... or at least the extra ones that don't plug into the motherboard. Just do a newegg search for fan controller and see which one you prefer.
August 12, 2011 2:49:27 PM

Thanks enigma, I had seen a previous reference to a separate fan controller somewhere in the forum, 'cos I do try researching before asking dumb questions, but I had no knowledge of where it fitted or what it can do.
Thanks for pointing me in the right direction.
I'll research this if there is no easier solution.
August 12, 2011 3:42:23 PM

Have seen a review showing how the VGA BRACKET is used on the Coolermaster HAF X Case, (Hardwarezone) so I'm OK with this. The Nvidia Edition case has the 5th GPU cooling fan already installed together with output duct so no need to worry about what the VGA bracket is all about, but the review does illustrate in detail how it is used if anyone else is as baffled as I was!
a b ) Power supply
August 12, 2011 9:27:21 PM

Start with this: any 3-pin fan can plug into a 4-pin outlet connector. You will find there is only one way to plug it in because of plastic tabs. They are arranged so that the first 3 pins connect to the correct ones. On a 3-pin fan, the color coding is: Black is Ground, Red is + VDC (varies to change the fan's speed), and Yellow is the fan motor speed signal. This last is a series of pulses (2 per motor revolution) generated in the fan motor and sent back to the mobo for monitoring. The mobo can use it to show you fan speed, and to make sure the fan is actually turning. It does NOT use measured fan speed to control the speed - control is based on measured TEMPERATURE. The CPU fan speed depends on a temp sensor built into the CPU, and the general case fan speed is based on a temp sensor built into the mobo.

Now for a complication. 4-pin fans are controlled differently, with slightly different signals, so that the pin that connects to the Red wire of a 3-pin fan may be fed +12 VDC at all times IF the mobo can only do speed control of a genuine 4-pin fan. This would cause the 3-pin fan to run at full speed all the time. SOME mobo fan control systems have ways to avoid that, though. Some automatically sense what type of fan is plugged into the mobo connector and alter their fan control strategy to feed varying voltage to that pin, just as a normal 3-pin fan control system would. Some are not automatic, but have a place in BIOS Setup where you can manually set whether you have plugged in a 3-pin or 4-pin fan. Check your mobo manual to see what it says.

Now to where to plug in. The mobo output connector labelled "CPU_FAN" should ONLY be used to plug in the CPU cooler, for two reasons. One is that it is the ONLY one whose fan speed control is based on the actual temperature inside the CPU. The other is that this one fan circuit often has a special extra feature for safety. It monitors the fan speed signal coming back on the Yellow wire. If it ever sees that fan stop, it does not wait for the CPU temperature to go too high. It anticipates that the CPU is in danger with no cooling fan running, and it will send out an alarm (usually a prolonged beep) and then completely shut down the system. If, for whatever reason, you choose to cool your CPU in a different manner and there is no fan plugged into this mobo pinout, systems like that MIGHT believe the CPU has no cooling and try to shut down. For those cases, mobos like this have a spot in the BIOS Setup where you can tell it NOT to monitor that fan speed.

The mobo pinouts labelled "PWR_FAN" are intended for a special set of wires coming directly out of your PSU that look just like 3-pin fan wires. Their function is simply to carry the fan speed signal from the fan inside the PSU to the mobo so it can be displayed and monitored. This pinout does NOT actually control the speed of the fan in the PSU - that speed control is done inside the PSU itself. NOTE that some PSU's do not have these special signal wires coming out; in those cases you normally would connect nothing to the mobo PWR_FAN pinout. However, on many mobos these PWR_FAN pinouts actually have +12 VDC on the pin that would "normally" be for the Red wire of a fan, so they CAN be used as extra fan power connection points. BUT they almost never have an speed control function, so any fan connected there will run at full speed all the time.

Case fans should be connected to the "CHA_FAN" pinouts on your mobo. They are the ones where fan speed is determined by the temperature measured on the mobo. Now, you have a common problem - more fans that pinouts of this type. With a bit of custom wiring modification you can solve this. You CAN connect TWO fans in parallel and plug then together into ONE mobo pinout. I advise not more than 2 per pinout, though, to allow for brief heavy current draw on start-up. When you do this, connect together both Black leads from the two fans, and then both Red leads. However, do NOT connect both Yellow leads together. Those leads each have pulse trains going back to the mobo for counting, and pushing two pulse trains in will cause big confusion. Leave ONE fan's Yellow lead connected to the connector you plug into the mobo; just leave the other fan's Yellow lead NOT connected to anything. This means the second fan of this pair will never have its speed recorded anywhere, so it will be up to you from time to time to be sure it is still working. Other than that, this will work just fine.
August 13, 2011 10:03:04 AM

Paperdoc said:
Start with this: any 3-pin fan can plug into a 4-pin outlet connector. You will find there is only one way to plug it in because of plastic tabs. They are arranged so that the first 3 pins connect to the correct ones. On a 3-pin fan, the color coding is: Black is Ground, Red is + VDC (varies to change the fan's speed), and Yellow is the fan motor speed signal. This last is a series of pulses (2 per motor revolution) generated in the fan motor and sent back to the mobo for monitoring. The mobo can use it to show you fan speed, and to make sure the fan is actually turning. It does NOT use measured fan speed to control the speed - control is based on measured TEMPERATURE. The CPU fan speed depends on a temp sensor built into the CPU, and the general case fan speed is based on a temp sensor built into the mobo.

Now for a complication. 4-pin fans are controlled differently, with slightly different signals, so that the pin that connects to the Red wire of a 3-pin fan may be fed +12 VDC at all times IF the mobo can only do speed control of a genuine 4-pin fan. This would cause the 3-pin fan to run at full speed all the time. SOME mobo fan control systems have ways to avoid that, though. Some automatically sense what type of fan is plugged into the mobo connector and alter their fan control strategy to feed varying voltage to that pin, just as a normal 3-pin fan control system would. Some are not automatic, but have a place in BIOS Setup where you can manually set whether you have plugged in a 3-pin or 4-pin fan. Check your mobo manual to see what it says.

Now to where to plug in. The mobo output connector labelled "CPU_FAN" should ONLY be used to plug in the CPU cooler, for two reasons. One is that it is the ONLY one whose fan speed control is based on the actual temperature inside the CPU. The other is that this one fan circuit often has a special extra feature for safety. It monitors the fan speed signal coming back on the Yellow wire. If it ever sees that fan stop, it does not wait for the CPU temperature to go too high. It anticipates that the CPU is in danger with no cooling fan running, and it will send out an alarm (usually a prolonged beep) and then completely shut down the system. If, for whatever reason, you choose to cool your CPU in a different manner and there is no fan plugged into this mobo pinout, systems like that MIGHT believe the CPU has no cooling and try to shut down. For those cases, mobos like this have a spot in the BIOS Setup where you can tell it NOT to monitor that fan speed.

The mobo pinouts labelled "PWR_FAN" are intended for a special set of wires coming directly out of your PSU that look just like 3-pin fan wires. Their function is simply to carry the fan speed signal from the fan inside the PSU to the mobo so it can be displayed and monitored. This pinout does NOT actually control the speed of the fan in the PSU - that speed control is done inside the PSU itself. NOTE that some PSU's do not have these special signal wires coming out; in those cases you normally would connect nothing to the mobo PWR_FAN pinout. However, on many mobos these PWR_FAN pinouts actually have +12 VDC on the pin that would "normally" be for the Red wire of a fan, so they CAN be used as extra fan power connection points. BUT they almost never have an speed control function, so any fan connected there will run at full speed all the time.

Case fans should be connected to the "CHA_FAN" pinouts on your mobo. They are the ones where fan speed is determined by the temperature measured on the mobo. Now, you have a common problem - more fans that pinouts of this type. With a bit of custom wiring modification you can solve this. You CAN connect TWO fans in parallel and plug then together into ONE mobo pinout. I advise not more than 2 per pinout, though, to allow for brief heavy current draw on start-up. When you do this, connect together both Black leads from the two fans, and then both Red leads. However, do NOT connect both Yellow leads together. Those leads each have pulse trains going back to the mobo for counting, and pushing two pulse trains in will cause big confusion. Leave ONE fan's Yellow lead connected to the connector you plug into the mobo; just leave the other fan's Yellow lead NOT connected to anything. This means the second fan of this pair will never have its speed recorded anywhere, so it will be up to you from time to time to be sure it is still working. Other than that, this will work just fine.

Thanks Paperdoc for your clear, detailed and helpful input, I'm sure it will be helpful to others also.
There aren't any fan connecters from the PSU, so I'm left with the five fans with only one dedicated 3pin CHA_FAN socket. This on the understanding that, of the remaining three, two being 3pin PWR_FAN sockets, and one 4pin CHA-FAN socket, none of which will definitely incorporate the speed control function. I'll use the dedicated one for the internal graphics card/motherboard cooling. The other three fan sockets I'll use for the four case cooling fans, two input and two output (one input and one output sliced together into one socket). I take your point that the PWR_FAN sockets may or may not provide speed control signals, so I'll take this into account.
I have looked at the manual, and as regards the 4pin CHA_FAN socket, unlike the 3pin - GRD/12V/Rotation; it has GRD/CHA FAN PWR/CHA FAN IN/+5V, but no reference as to its intended use.
I've initially tested the fan rotation on a clean MoBo with only the CPU installed and connected to the MoBo. All fans rotate except the CPU fan but this is probably due to it not receiving a temperature control signal from the MoBo.
Thanks again for your help; I now feel comfortable with the case cooling configuration and I've always felt that it was of fundamental importance to a successful gaming rig. If you see anything wrong with my intentions, please let me know.
a b ) Power supply
August 14, 2011 2:16:49 AM

First, it IS possible that your 4-pin CHA_FAN mobo connector will provide speed control to a 3-pin fan plugged into it. Some mobos can do this, some cannot.

I'm a little surprised that the CPU cooling fan connected to the CPU_FAN mobo output did not turn. MAYBE, as you say, you had it turned on only so briefly that the CPU never warmed up enough to call for cooling. Next time you try, navigate quickly to the BIOS Setup screen that shows you temperatures and fan speeds and watch the CPU temp, and see whether that CPU fan comes on after a minute or less.

For your reference, here is how 4-pin fans and their connectors work:

http://www.allpinouts.org/index.php/Motherboard_%28CPU%...

See how the wire colors are different, but in both case Pin 1 is Ground, Pin 2 is +VDC, and Pin 3 is speed (pulses) signal from fan back to mobo. On a 4-pin system, Pin 4 carries the PWM (Pulse Width Modulation) control signal. This is an on/off (square wave) type of signal that has variable % On time. Within the 4-pin fan's motor casing there is a tiny control circuit that uses this signal to switch the +VDC line on and off to the motor rapidly, accomplishing motor speed control. For this reason, in 4-Pin control mode the Pin 2 signal is always kept at +12 VDC and the control circuit, using the PWM signal, regulates power to the motor. In 3-Pin control mode, the Pin 2 voltage varies to achieve motor speed control, and there is no PWM signal involved. Because of this, IF the 4-Pin output from the mobo can ONLY do 4-Pin mode, a 3-Pin fan WILL run, but always at full speed. However, it is not too difficult for a mobo maker to arrange to have two possible control modes (3- or 4-pin) feed out to a mobo connector, thus allowing speed control for either type of fan. It just depends whether your mobo maker did this or not.

If you have not noticed, almost all fans have two arrows on their cases. One points around the case in the direction of blade rotation. The other points front-to-back to indicate the direction of air flow. All of this, of course, IF the fan motor is connected correctly to + and Ground lines. This is helpful to guide you in mounting the fans in the case and to verify wire connections.
August 14, 2011 12:27:19 PM

Paperdoc said:
First, it IS possible that your 4-pin CHA_FAN mobo connector will provide speed control to a 3-pin fan plugged into it. Some mobos can do this, some cannot.

I'm a little surprised that the CPU cooling fan connected to the CPU_FAN mobo output did not turn. MAYBE, as you say, you had it turned on only so briefly that the CPU never warmed up enough to call for cooling. Next time you try, navigate quickly to the BIOS Setup screen that shows you temperatures and fan speeds and watch the CPU temp, and see whether that CPU fan comes on after a minute or less.

For your reference, here is how 4-pin fans and their connectors work:

http://www.allpinouts.org/index.php/Motherboard_%28CPU%...

See how the wire colors are different, but in both case Pin 1 is Ground, Pin 2 is +VDC, and Pin 3 is speed (pulses) signal from fan back to mobo. On a 4-pin system, Pin 4 carries the PWM (Pulse Width Modulation) control signal. This is an on/off (square wave) type of signal that has variable % On time. Within the 4-pin fan's motor casing there is a tiny control circuit that uses this signal to switch the +VDC line on and off to the motor rapidly, accomplishing motor speed control. For this reason, in 4-Pin control mode the Pin 2 signal is always kept at +12 VDC and the control circuit, using the PWM signal, regulates power to the motor. In 3-Pin control mode, the Pin 2 voltage varies to achieve motor speed control, and there is no PWM signal involved. Because of this, IF the 4-Pin output from the mobo can ONLY do 4-Pin mode, a 3-Pin fan WILL run, but always at full speed. However, it is not too difficult for a mobo maker to arrange to have two possible control modes (3- or 4-pin) feed out to a mobo connector, thus allowing speed control for either type of fan. It just depends whether your mobo maker did this or not.

If you have not noticed, almost all fans have two arrows on their cases. One points around the case in the direction of blade rotation. The other points front-to-back to indicate the direction of air flow. All of this, of course, IF the fan motor is connected correctly to + and Ground lines. This is helpful to guide you in mounting the fans in the case and to verify wire connections.

Thanks for the reply Paperdoc.
I made the assumption that the CPU fan did not run because, apart from the CPU and MoBo, there was nothing at all within the case, therefore no work for the CPU to do. Next time I connect the main power cable I'll wait a few minutes to see if it brings the CPU fan in. Even then I'm guessing it may still not work until I install an operating system and stick a game in the drive.
Since our last correspondence, I have fitted everything in the case other than the GPU, which I have yet to buy along with the OS. Knowing basically nothing of computers and how the system will operate, I will have lots more reading, researching, and testing to do before finally commissioning, so it will be some time before I experience problems.
The link you gave me was clear and simple to understand, well worth reading.
When I checked the chassis fans , I only checked power supply to rotate impellor. I have yet to buy a fan to MoBo duel splitter to connect the last two fans, then I'll check directional rotation. Don't think I'll be able to do much about the speed control until I learn something of the BIOS.
Thanks again for you help; sure appreciate your comments.
!