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4pin, 3pin... How Does It Work?


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#1 InspectorMustache

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Posted 21 February 2011 - 10:30 PM

Hey everyone!

I'm sorry, I've searched the forums and all that and I even found some threads about this but somehow I still don't get it.

I want to install a 80mm 12V case fan in my XBox. Now, the specs say this fan has a 4pin wire and if I remember correctly there's a 3pin connector inside the XBox. So can I get this fan to work anyhow? If so, how? Do I need an adapter? What kind? One that looks like this? How does that work? Do I need to connect it to the HD/HD power cable? If so, do I need to get a Y cable?

Also, will I still be able to change the fan speed via the dashboard (or the bios) with this?

Alright, hope someone can clear things up for me.

Thanks in advance!!

#2 obcd

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Posted 22 February 2011 - 12:40 AM

I have no experience with a 4 wire fan. in case of a 3 wire fan, you have power, gnd and speed pulses. The power is turned off rapidly to reduce the fan speed (in case of the original fan connector)
I don't think there is a speed pulse detection to actual measure the fan speed in the xbox.

The xbox disconnects the gnd rapidly to reduce the fan speed. To use the speed pulses, you need to disconnect the power site.

A 4 wire fan needs PWM pulses to run. Don't use such in your xbox. 3 wire shouldn't be a problem, just don't connect the speed pulses wire.

If you power the fan from the harddisk supply connector, it will always run at full speed. This can be a noisy situation.

The adapter will also only work with 2 and 3 wire fan's. They will also always run at full speed.

regards.

Edited by obcd, 22 February 2011 - 12:42 AM.


#3 GSCOMPS

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Posted 22 February 2011 - 02:33 AM

You should be able to directly plug in the four pin fan into the 3 pin socket, if your box is modified you can control the fan speed with the dash board.

Most four pin fans are backwards compatible so it shouldent hurt to test it. Worst case scenario the fan will need a PWM circuit to run and the fan will not spin without it.

IPB Image


For what its worth, if the fan you have now needs PWM to run, just buy another standard 80mm fan

#4 memainman

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Posted 22 February 2011 - 08:00 AM

if i remember correctly, fan speed is altered on the gnd pin and sensed on the left pin. (in the case of the xbox.) if you want to connect a 4 pin fan to a 3 pin connector, then its just a matter of figuring out which wire is pwr+ and which is the gnd.
once you have, cut off the connectors of each fan about an inch from the connectors, splice the wires on the new fan to the corresponding wires on the 3pin connector of the old one. use the image you linked to as a guide to figure that out. then just put some elec tape/shrink wrap tube over the remaining unused wire on the 3pin connector (this should be the sensor wire). now just plug it in and let her rip.
however, your xbox no longer has any way to tell how fast your fan is going so you will need to alter it manually in your dashboard. set it to about 60% im pretty sure and the fan will change speed accordingly.
if it wont move, youve got some wires mixed up. (i cant remember if the sensor wire needs to be terminated however, can someone confirm??)
good luck.

#5 InspectorMustache

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Posted 22 February 2011 - 05:09 PM

Thanks for your help, guys! Actually, I haven't even ordered the fan yet. The model I had in mind was the SilentWings from be quiet! (a German manufacturer, I think). It's a little bit more expensive but it's high-quality and pretty silent (well, quiet). There are different versions (check those out here), all of which are 3pin except for the PWM version which is 4pin (that's actually what makes it PWM, if I understood correctly). I didn't really know what PWM was all about and thought I needed that in order to control the fan speed via the dash/bios. But if I understood obcd's post correctly the XBox controls the fan speed through the gnd wire. So I 'm just gonna get the standard 3pin version and should be fine, right?

#6 memainman

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Posted 22 February 2011 - 11:11 PM

oh, i thought you meant 4pin as in molex >.>
ignore my previous post biggrin.gif

#7 obcd

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Posted 23 February 2011 - 10:27 AM

Go for a 3 pin type, and you will be fine.
Most manuals that come with a pc motherboard will show you the fan connectors and the pinout.
Usually, black is GND, and the wire just next to it is the supply wire. As far as I remember, the xbox doesn't use the speed pulses, so you shouldn't connect the third wire. (If the original fan was only having 2 wires, the third one isn't used.)

regards.

#8 InspectorMustache

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Posted 26 February 2011 - 12:54 AM

Alright, thanks! I've installed the fan by now. I cut the yellow wire (speed pulse) before connecting the fan. Seems to work fine and is extremely quiet. Nice!

But: At normal speed (1.0 in UnleashX) the CPU temperature was at 69 C in no time. Since I want to be able to run the XBox with the modchip off (without the ability to adjust fan speed), I think I might as well connect it to the hard drive via the 4pin-molex adapter that came with the fan. If I do that, it will turn at full speed all the time, right? Will this also work now that I've cut one of the wires?

Again, thanks for your help! Made this installation a lot easier.

#9 obcd

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Posted 27 February 2011 - 08:35 PM

The yellow wire doesn't make a difference (leave it disconnected).
The harddisk molex connector has 2 voltages.
The yellow wire is 12V and the red wire is 5V.
If you connect the blower to the 12V, it will run at full speed. It might be a little noisy that way.
(Unless it is a really low noise type. They rotate slower and produce less airflow at their normal operating voltage.)

It's also possible that you have a problem with the thermal compound between the cpu and it's heatsink. If that dried out, the heat of the cpu isn't transferred good enough to the heatsink causing the high cpu temperature.

Some dashboards used to display a wrong cpu temperature in the early days. You might google for that issue to see if the cpu is really getting that hot.

regards.

#10 InspectorMustache

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Posted 04 March 2011 - 03:47 PM

Yeah, it's kinda strange. I get much lower temperatures in XMBC than in UnleashX (both the most recent versions). I will look into both that dashboard temperature issue and replacing the thermal compound. I might add a resistor to the supply wire to keep the fan at a good average speed.




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