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Modding Fan Wiring

D

DougWD

Limp Gawd
Joined
Sep 4, 2005
Messages
502
This is a tripartite question:

(1)
I have a Molex connector that came with my GTs. Male to female, and then a black and red wire coming out of the black and yellow leads of the male side. The black and yellow leads terminate in a 3 pin male connector. Then out of the three pin comnector one yellow lead comes out and terminates in a female three pin connector.

The molex is the 8981 standard YBBR or 12v Ground Ground 5v.

So the single yellow lead going to the three pin connector is for RPM, and I assume if I plug the yellow lean into the MB three pin sys fan header, it will then rad the rpm of the fan? Why would they do that? Why not just plug the yellow, black, and red three pin connector into the MB header? I can't figure out their logic here.

(2)
MBs have only one PWM connector (4 pin), and that's for the CPU fan. The other MB fan connectors are 3 pin power/rpm.

Fans come in only four configurations:
1. 12v
2. 12v w/RPM sensor
3. 12v wRPM sensor and PWM (4 pin)
and
4. 12v with thermal sensor (with or without an RPM sensor)

Now if you have a fan w/o the PWM wire, you're simply out of luck getting it to work with a MB/PWM. The only thing you can do is run it at full speed, or reduce the voltage going to it. There is no other way to control speed or speed vs.heat.

But what if you bought PWM fans, such as the Gelid 120 Silent series PWM. If the MB CPU 4 pin header puts out enough voltage, could you some way run all your fans off the 4 4 pin CPU connector by splicing the fans in some way? And does the CPU fan header put out enough voltage?

(3)
Now there is one other way to control the speed vs temp, and that's with software. Speed fan comes to mind, but MB manufacturers have their own flavor of speed fan, such as Gigabyte's Easy Tune.

The problem with software is that it's hard to get them to read all of your fans. You really have to mess around to get them to work. Speed fan, for example, will read the CPU fan well, and usually one other fan plugged into the motherboard, but then the fun starts.

So if you could wire all of your case fans into one header on the MB and use a single RPM sensor, you could use one fan's speed to modulate the rest. In other words, speed fan would see one fan's RPM, and since all the fans are connected to one fan header, it would lower all the fan speeds at once. I know fan headers, other than the CPU header which I don't know, will give you something like 20+ watts, and fans take like 1.5w each.

So you have two options, IF you can wire all fans to one header.

Buy all 4 pin PWM fans, and splice them all into the CPU header so that all your case fans are modulated by CPU temperature, or use all 3 pin fans wired into one MB header and let software control one RPM and ALL fans.

Question: Have I totally misunderstood fan wiring or can this be done?
 
Before I start, a comment. Yep, Yep. This is why someone made millions on the first fan controller accessory. Instead of dealing with the issue I found refurbished fan controllers (people never seem to pay attention to the power limits) for $4 and bought a lifetime supply.

Now a little rant;
It is retarded that enthusiast motherboard manuf (Abit was the exception) do not provide more headers and better control of them in the bios. I know that bios programming space is limited but if a certain company actually sat down and rewrote the bios from scratch instead of band-aid patching 25 year old code ...


1) they have tried to provide a universal power adapter, I know it makes little sense but back in the old days some fan headers could not handle high powered fans, so with the male-female molex they expect you to power the fan with the molex pass through getting power directly from the Power Supply and then use the single yellow RPM 3 pin to go to a board header to monitor the rpm. Yes, today, it makes little sense but that 'adapter' has been around a for a while and they throw it in to try to cover every situation that might come up.

2-3) The way I read it questions 2 and 3 are basically the same. Yes in theory it is possible as long as you do not exceed the current capability of the motherboard fan header. For non-pwm fans it is absolutely possible but not commonly done as burning out the CPU fan header is not something many people care to even remotely chance. Also with high powered video cards and some enthusiast case designs it might not even be desirable to have all case fans controlled by the CPU fan header. But in general, for non-pwm fans, other than total current draw (if you kept that at or under 1A total, one could look as see in the Intel Thermal and Mechanical Guidelines for Intel's specs on CPU fan header amperage and assume the manuf at least met that and I believe it is 1A) what you propose will work. I take no responsibility.

For PWM fans the same basically holds true up to a point. At some point the "sharing" of the pwm signal by several fans may degrade the pwm signal so much it will no longer trigger the fans. No clue what that point is. I recall several posts of 2 fans running off of the same pwm signal. I do not know enough about the pwm signal (drive strength, impedance matching, etc. ) to guess at how many fans could be run and if the circuitry creating the signal could/would be harmed by the load or impedance presented by a bunch of fans in parallel connected to it. /shrug. On the other hand the circuit design could be such that it is not very sensitive to what is loading it and could possibly run a zillion fans. I just do not know. If I where to try it I would want identical pwm fans throughout.

Someone out there has tried this, hopefully they will comment.
 
If you grab power from the header, just make sure to size them conservatively to take into account startup current. Max current of fans should be at most half of the max rated current of the mb header.
 
I just installed 5 AC F12 PWMs a couple days ago and I'm impressed. Ewiz had them for $4.50 each so I had to buy some ^_^. CPU, back, side, 2 front powered off the cpu 4 pin. Very nice and quiet at 50%, I think they were running around 650 rpm. Runs full speed if cpu hits 45C. Lowered my voltages and overclock a bit (3.7 to 3.4) and I haven't heard them spin up in games. Did some stress testing for a while to make sure it works and it does. I didn't even know my computer was loud before I installed these :eek:. Only reason I was shopping for a fan was because one of my yateloons started grinding. The daisy chain pwm system seemed like a spiffy setup and the price was cheap so I replaced everything ;).
 
Nice find, was not aware of that.

Interesting, I wonder if there is something in the fans pwm circuitry that enhances sharing the signal or it is just a fancy wiring harness ? But anywho, $10 bucks/fan (they are good quality fans) is not bad.

http://www.coolerguys.com/840556091165.html


If you grab power from the header, just make sure to size them conservatively to take into account startup current. Max current of fans should be at most half of the max rated current of the mb header.
Click to expand...

Thats a very good point, I looked but could not find the current/wattage specs. If I had to guess I would estiamte .1 A running and thus .2A startup which would make 4 + 1 for the cpu about all I would try from the cpu fan header unless I had info from the board manuf that the header was rated to put out more than 1A.
 
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Now I'm paranoid running my 5 F-12s off the 4pin :eek:. I was going to get the pro version for the exhaust, but decided just to get all the same standard mounting ones.

Here's a list of the F-12 pwms they still have. Never bought anything from ewiz before, but the price is good. Shipping was around $9. Seemed a day or so slower than Newegg at getting things shipped out, but overall was a smooth purchase.

http://www.ewiz.com/query.php?categry=0&s=arctic+cooling+F12+pwm&x=0&y=0
 
Zoomer said:
If you grab power from the header, just make sure to size them conservatively to take into account startup current. Max current of fans should be at most half of the max rated current of the mb header.
Click to expand...

Really good point.
 
For those who have a Gigabyte X58 series, they have two PWM risers plus the CPU. I have no idea how the PWMs other than the CPU ramp up. The Gigabyte X58 board, if I remember correctly, has no way to BIOS ramp the fans manually according to temp. Anyone have any information on this?

Correction--It only has ONE extra. Also, the CPU doesn't ramp the fan, it's just wide open all of the time.
 
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For those of you using this type of technique, but not using the AC fans, what type of harness system are you using? Where can I get some?

BTW, the gelid fans I ordered just came in. both the PWM and the TC version are rated at 58CFM at 1500RPMs with a static pressure of 1.6 and a maximum noise level of 25.5dBA. These things come with a five year warranty.
 
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http://www.arctic-cooling.com/catalog/tips_and_tricks.php?tPath=7&aID=521

That's the AC manual for installing the fans in a series, but I'm not understanding the section on separate fan speed lines. All the fans are the same, so they should spool the same RPMs. So why would you need a separate PST for the case fans? I mean if that would separate the 4 case fans from the CU fan, then I suppose yuo would know if all four fans were out. Other than that, I'm not getting it.
 
BillParrish said:
Thats a very good point, I looked but could not find the current/wattage specs. If I had to guess I would estiamte .1 A running and thus .2A startup which would make 4 + 1 for the cpu about all I would try from the cpu fan header unless I had info from the board manuf that the header was rated to put out more than 1A.
Click to expand...

I remember looking in a mb manual and find that speced. Of course, that was around the time when the limit was 0.5A, and some guy who attempted to run a large delta fan off these connectors found that his motherboard didn't like it very much.

These days, 1A would probably be safe. We could try having Kyle or someone ask the mb manufs.
 
Most Gigabyte/Asus motherboards I've owned have had upwards of 20W ratings on their fan headers. It will vary with each motherboard, so definitely make sure to check.
 
Arctic Cooling says you can run "up to" five of their 120 fans. I assume that would be half the total 1A limit, and that would mean the fans are about .5 amps each, of just a tad less. That may or may not stand true with all fans of that size. I'm only going to run three.

I bought the Gelid Y connector and one Arctic Cooling fan that has the Y connector already on it.
1. Gelid 120 PWM
1. Cogage CPU fan
1. Arctic Cooler PWM.

Should be fine.

Can anyone tell me how to speed up or slow down the fan speed using Speed Fan? I have my fans labled and I can see them in SF, but I don't see any throttles.
 
MisterSparkle said:
Do some googling for Speedfan Guide, should be some results to your liking.
Click to expand...

I just did. I think my PWM circuit is burned out. Nothing will adjust the CPU fan using PWM. I'm going to switch it to Voltage in BIOS and see if that works.

I really hope the next generation of MB allows us to dial in CPU fan speed in relation to CPU heat. You would think . . . .
 
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