How to utilize on-board fan speed control when your fan has the wrong connector

By VvWolverinevV
Dec 29, 2007
  1. How to utilize motherboard fan speed control when your fan has the wrong connector

    I recently ordered the Vantec TD9238H case fan, appropriately named "Tornado." After it arrived, I soon learned the misleading spec on Newegg "Power Connector: 3/4 Pin" actually means "4-pin connector, with the RPM sensor in a separate 3-pin connector." Since the 4-pin connector is always at 12V, the fan was always at maximum speed, and the "Tornado" was so loud I couldn't even hear my own thoughts. Rather than go through the hassle (and delay) of returning it, I decided to make it work. Here's how (soldering required):

    1. Obtain a 3-pin connector (for example from a failed fan).
    2. Solder as follows:
      • P1(ground/black) from 3-pin connector to ground from fan connector (black for the standard 4-pin Molex connector)
      • P2(12V/red) from 3-pin connector to 12V from fan connector (yellow for the standard 4-pin Molex connector)
      • P3(RPM sensor/yellow or white) from the 3-pin connector to RPM sensor directly from fan (usually yellow or white) *Note: this step is not required if your motherboard fan speed control does not use feedback from the fan. This was the case for my Compaq Presario where fan speed is only dependent on CPU usage.*
    3. Plug the 3-pin connector onto the motherboard fan speed control pins. (The original connector should not be plugged in).

    So far, this has been working fine for me. Feel free to reply with any questions/comments :D
  2. mailpup

    mailpup TS Special Forces Posts: 7,188   +470

    One thing isn't clear to me. Isn't the 3 pin connector supposed to be plugged into the motherboard. Some, though not all, motherboard fan power feeds have a sensor for the 3 pin connector that comes with the fan. The molex is an alternate power feed for the fan, although as you said always full speed.

    Did you not have a free motherboard connector or was the cable too short? Maybe I just misunderstood.
  3. VvWolverinevV

    VvWolverinevV TS Booster Topic Starter Posts: 119

    My fan only came with a Molex connector (no 3-pin connector). Well... there was a 3-pin connector, but only the sensor wire was fed into it. The other two slots didn't even have contacts!

    My apologies if "on-board" means something other than "motherboard." I edited the OP.
  4. vegasgmc

    vegasgmc TechSpot Chancellor Posts: 1,377

    The 4 pin Molex connector is plugged into one of the lines from the power supply and the small 3 pin connector goes to the motherboard, usually any connector but some are labeled "case or aux" . You also may have to enable fan speed control in the BIOS and install Cool N Quiet if you have an AMD processor.
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