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04-15-11, 12:08 AM #1
2 4 pin pwm fans on a splitter to motherboard?
I can't find any conclusive evidence of whether it would work or not if I put 2 4 pin pwm fans on a 4 pin pwm y splitter cable in plugged them both into the cpu fan header on my motherboard. I know it can hurt the motherboard if you over draw so how do I know? I've been through the manual and checked the specs online as well but can't find anything certain. It's a gigabyte ex58-ud3r motherboard and I want to have 2 scythe kama 1600rpm fans on pwm together on my megahalems. here's the fan. it draws 1.32w at peak. thoughts?
http://www.newegg.com/Product/Produc...-161-_-ProductIntel 5820K @4.375ghz @1.21v~Asus X99-a usb 3.1~Corsair H90Gskill Ripjaws V ddr4-3000Gtx 980 ti amp extremeDell U2713HMSamsung 950 pro 512gb~WD blue 1tbPioneer BDR-206Corsair AX850Fractal Define R5Leopold Tenkeyless~Deathadder 2013Harman Kardon HK990~Denon AH-D7000
04-15-11, 12:24 AM #2
That should be fine.
I don't know of any mobo headers rated for less then an amp, and one amp at 12v is 12w.
You'll need to make sure only one fan is feeding tach information to the mobo if you want the tach reading to be anywhere near accurate.
04-15-11, 12:25 AM #3
You should be fine, if you wanted to be super-fine you could split the PWM wire (4th pin) from the mobo, run an rpm wire from 1 fan to the mobo, then power the fans direct from the PSU and this would allow the mobo to effectively control the fans while not having to worry about power draw (also is, imo, the RIGHT way to do this)
04-15-11, 12:33 AM #4Intel 5820K @4.375ghz @1.21v~Asus X99-a usb 3.1~Corsair H90Gskill Ripjaws V ddr4-3000Gtx 980 ti amp extremeDell U2713HMSamsung 950 pro 512gb~WD blue 1tbPioneer BDR-206Corsair AX850Fractal Define R5Leopold Tenkeyless~Deathadder 2013Harman Kardon HK990~Denon AH-D7000
04-15-11, 12:35 AM #5Intel 5820K @4.375ghz @1.21v~Asus X99-a usb 3.1~Corsair H90Gskill Ripjaws V ddr4-3000Gtx 980 ti amp extremeDell U2713HMSamsung 950 pro 512gb~WD blue 1tbPioneer BDR-206Corsair AX850Fractal Define R5Leopold Tenkeyless~Deathadder 2013Harman Kardon HK990~Denon AH-D7000
04-15-11, 12:37 AM #6
If you look close at the pictures of this y splitter only one of the plugs has a 4th pin (pwm?) Looks like it might work!
04-15-11, 12:48 AM #7
Yup, that splitter does what you want it to with the tach pin. It should work great.
04-15-11, 12:54 AM #8
04-15-11, 09:09 AM #9
Hi im ruunnign a similar set up with a couple of sythes in push-pull on a megahalems. whats the effect if I was to just "cut" one of the rpm cables so its effectivly a 3 pin set up & only "1" fan is being read off the 4th pinBeer will get you through times of no money better than money will get you through times of no Beer.
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04-15-11, 11:47 AM #10
04-16-11, 08:50 AM #11
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Before you cut any wires, try pulling the pin out of the connector. There should be a set of small holes along one side of the connector, one for each pin, that you can insert a small paperclip into in order to release the pin from the connector housing. Then you can simply fold it out of the way and tape it down. This will allow you to keep the wire intact for future use, if you should ever want to use the rpm sense again.
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04-22-11, 01:00 AM #12
Before you go cutting anything, PWM spliter power cables are made so that 4 wires goto 1 fan and 3 wires go to the other fan, the MB reads RPM info from only 1 of the 2 fans connected but has the PWM wire going to both fans.
If the power spliter cable is 3 wire only, it won't work on PWM fans.
04-23-11, 08:55 PM #13
it worked out great. motherboard didn't start smoking or anything and the fans are spinning over 100rpm slower during prime95 small fft's than with one fan. also one less place i have to run a big @$$ molex from the power supply and it's nice and quiet until it has reason not to be.
04-24-11, 02:50 PM #14
Ok not sure what to make of this. HWmonitor randomly shows the cpu fan at 0 rpm off and on but i have the side of the case off and the fans are clearly spinning. huh?
edit; idk it doesn't happen in bios so nvm. i guess hwmonitor is crap. it also says my 12v rail is at 2v LOL
Last edited by Brando; 04-24-11 at 04:04 PM.
04-24-11, 08:12 PM #15
HW monitor is fine, I bet you have both RPM wires running interfering signals.
04-24-11, 09:27 PM #16
There's only one rpm wire. One of the fan plugs has 3 pins instead of 4. It's this one.
I watched fan speed in bios for 15 min waiting for fluctuations and nothing. Only hwmonitor does it. Also, 12v rail shows 10v low yet my pc works great.
04-24-11, 09:29 PM #17
04-24-11, 10:31 PM #18
edit:so far so good. straightened the pins as much as possible, switched fans, and plugged\unplugged a few times. no false readings yet. maybe too much anti oxidation coating or whatever they call it if any. reminds me of the time i bought a mag lite and it wouldn't turn on even after switching batteries. then i rubbed the spring against the battery contact plate for a minute and it miraculously started transferring electricity between the 2 surfaces. idk.
Last edited by Brando; 04-26-11 at 11:05 PM.