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Slowing Down Molex Case Fans

Discussion in 'Overclocking & Cooling' started by Vern1961, 27 Sep 2009.

  1. Vern1961

    Mobster

    Joined: 29 Mar 2007

    Posts: 4,036

    Location: Swindon UK

    Just wanted to reprise a topic which I know has cropped up from time to time. Basically, the side and rear fans in my (cheap) case are wired direct to the 4 pin Molex from the PSU, no speed control at all. I've lived with the noise for about 10 months but it's starting to get a bit intrusive to be honest.

    I know there's a mod that can be done to reduce the voltage from 12v to 7v but I'm a bit loathe to start chopping around Molex leads.

    So the questions are:
    1. Is there any proprietary resistor device I can buy to insert between the power supply and fans to slow them down.
    2. Is it possible to adapt the Molex to run off the motherboard 3 pin fan socket and will this have enough power for a 120mm + 80mm fan?
    3. Would I be better just buying two replacement fans with 3 pin connectors?

    Any suggestions gratefully received. Moral of story is next time buy a case which doesn't stint on the power arrangements for the fans...
     
  2. PhillyDee

    Capodecina

    Joined: 12 Feb 2007

    Posts: 14,169

    Location: South Shields

    2. Yes, you can buy converters, Or chop the connector off and put your own on.
    3. Thats the easiest way

    Its easy enough to change to 7v, just remove one pin from the 0v and put it into the 5v. And if it has a through connector, either glue it up, or chop it off, as you dont want that to be accidently connected to any other device!
     
  3. JonJ678

    Capodecina

    Joined: 22 Dec 2008

    Posts: 10,371

    Location: England

    1/ yes, though you could solder a resistor inline instead. i have a few which came with a zalman fan.

    If you have a very short molex male to fermale lead you can move pins around on that instead. The idea is 12-5=7V and almost all fans run at 7V
     
  4. Mr-White

    Capodecina

    Joined: 12 Nov 2002

    Posts: 14,625

    Location: In my own little world

    You can buy fan controllers that allow up to adjust the fan speeds at the turn of a nob but it's pretty easy to 7v mod fans, literally all you need to do is swap over 2 wires.

    The reason some fans are 4 pin moles and not 3 pin mobo is they draw too much power.

    MW
     
  5. Vern1961

    Mobster

    Joined: 29 Mar 2007

    Posts: 4,036

    Location: Swindon UK

    Well I've decided to go for swopping out the fans (actually 3 x 80, front, rear and side) with 3 pin versions. Now my mobo has two spare fan sockets CHA_FAN and PWR_FAN. Which fans should I connect to which socket and is it possible to purchase a splitter cable as obviously two fans will need to be run off the same socket?
     
  6. JonJ678

    Capodecina

    Joined: 22 Dec 2008

    Posts: 10,371

    Location: England

    It's certainly possible to run many of one header, but not recommended. It is possible to kill boards by drawing too much power from these headers. The cha_fan will behave as you expect, the pwr_fan may run it at 12V all the time, or not at all, as it is likely to be for monitoring psu fan speed.

    I'm pretty certain the solution you want is to run the existing ones at 7V via the standard mod, or to get a fan controller.
     
  7. setter

    Caporegime

    Joined: 14 Dec 2005

    Posts: 28,160

    Location: armoy, n. ireland

    The PWR fan socket will run the fan at full speed all the time, 7v mod the fans or a cheapy controller such as the akasa junior would be a good investment.
     
  8. ns400r

    Mobster

    Joined: 23 Apr 2004

    Posts: 3,580

    Location: UK, Near the middle......

    Altering the molex wiring would have worked. Convert the fans to 7v instead of 12v.
     
  9. Vern1961

    Mobster

    Joined: 29 Mar 2007

    Posts: 4,036

    Location: Swindon UK

    Well I've ordered the fans from OCUK now (it's actually 2 x 120 for front/rear and 1 x 80 for the side). I would hope CHA_FAN could provide enough output to drive the two 120 fans particularly if I enable Q-Fan. Guess I will see what happens if I connect the side one to PWR_FAN. I've still gone for replacement as they are all Akasa fans so hopefully quieter anyway even at full rpm than the cheapo original case fans.

    I'll almost certainly purchase a fan control unit though - out of interest I presume the input to these is from a Molex 4 pin then the settings are user controlled on the front panel - i.e. no connection to the mobo at all?
     
  10. PaulyD

    Mobster

    Joined: 24 Mar 2008

    Posts: 4,635

    Location: High Wycombe

    Yep, fan controller will receive power and then you connect the fans to that
     
  11. GSS

    Associate

    Joined: 9 Sep 2009

    Posts: 21

    Does your mobo support PWM (4 pin header for CPU Cooling)?...If it does the cha_fan header should allow you to control the speed of any fan attached using the Asus Q-Fan utility.

    I have a PN5-D from Asus that supports a 4 pin PWM fan connection, it has a further two 3 pin headers, cha_fan1 & cha_fan2. I have Q-FAN 2 software and I am able to choose from 4 different settings (Disabled > Performance > Optimal > Silent), for any fans connected to the cha_fan1 & cha_fan2 headers. The 3 pin power header on my mobo, I believe is 12v and runs a fan at it's full RPM, Q Fan 2, displays the speed of the fan connected to the power header but you cannot control it.

    I'm going to use my mobo fan headers to run component fans that are connected to the board only and my intake, exhuast chassis fans via a 5.25" bay controller.

    This is how I intend to use my mobo fan headers;

    4 pin CPU_PWM = CPU OCZ Vendetta Cooler 92mm fan
    3 pin CHA_FAN1 = Mobo Chipset (system temp) 60mm fan
    3 pin CHA_FAN2 = 2 x Coolink GFX Chilla GPU Coolers (SLI'd Graphics) via a splitter cable
    3 pin PWR = RAM OCZ XTC Cooler

    Your mobo manual should have specs for the maximum fan power the board supports.
     
  12. Vern1961

    Mobster

    Joined: 29 Mar 2007

    Posts: 4,036

    Location: Swindon UK

    Can't find any reference to PWM in the Mobo manual. Guess the P5 SE version just doesn't have all the features. At the moment I'll connect the two x 120 fans for front and rear to the CHA_FAN thus get the speed control. The side fan can go on PWR_FAN and if that doesn't work or it's too noisy at speed I'll switch it to a Molex via adaptor with the 7v mod.
     
  13. Vern1961

    Mobster

    Joined: 29 Mar 2007

    Posts: 4,036

    Location: Swindon UK

    Postscript...

    Well now, here's the thing and it proves sometimes you forget to check the most obvious possibilities before replacing expensive components.

    It wasn't the case fans as the howling fan noise was still present after changing them out. Well at least I have 3 new Akasa case fans and OCUK got £20 of business. Shiny.

    Attention then turned to the GPU having read that BFG 8800's have a reputation for noise. However after playing around with Ntune it became obvious not the GPU fan either.

    On a hunch, I went into BIOS and discovered I'd not switched Qfan on (the ASUS Mobo disabled by default). After enabling and selecting silent - hey peace and quiet from my rig. It turns out that screaming banshee noise was the AC Freezer running at full tilt.

    So if like me you're trying to cure the noisy fans in your case, make BIOS the first stop to check all the intelligent fan controls are swiched on.