The great PSU fan swap of 2008

Seasonic power supplies are great. Whether they’re units the Taiwanese PSU manufacturer sells under its own name or those it makes for other firms (like Corsair), they have a reputation for quality, efficiency, and low noise levels—something we’ve confirmed in our testing. However, like all power supplies, they’re vulnerable to fan problems. In the case of my Seasonic S12 430W, the 12 cm fan that had been happily spinning away for the past year and a half suddenly started clicking, like a folk music artist randomly kicking off a washboard solo every so often.

When this type of problem hits a regular case fan, it’s usually not too big of a deal—just remove the faulty fan, try cleaning it and oiling it, then purchase a replacement when you find that it still makes the noise despite your best efforts. With a PSU fan, though, things are more complicated. The cooling device sits inside the PSU itself, usually next to large capacitors and under a sticker that says “Warranty void if removed.” What is one to do in this case?

If you answered, “Get in touch with the PSU manufacturer and try to get a replacement,” you’re pretty much dead on. That’s by far the safest and most sensible course of action. However, some of us aren’t particularly sensible or worried about safety. Me, I just don’t have time to get into lengthy customer service shenanigans, especially when the machine at stake is my primary work system. I briefly weighed the options of voiding my warranty or having to ship my power supply off who-knows-where and wait until who-knows-when for a replacement, and I settled on the former.

I looked around a few relevant sites and forums (including the helpful Silent PC Review forums) to get an idea of what kind of fan I should pick as my replacement. In the end, I ended up going Scythe’s S-Flex SFF12F. This model has almost the same default rotational speed at 12 volts as the Seasonic PSU’s stock Adda AD1212LB-A73GL (1600 RPM instead of 1800 RPM for the Adda), but it has a high-quality Sony fluid dynamic bearing, and it seems to be a favorite among the quiet-PC crowd. I didn’t want to pick something too slow, since the S12 regulates fan voltage depending on load, and I was worried about a slower model not starting up at lower voltage settings the S12 might pick when my system is at idle.

Armed with the S-Flex, I popped open my case and mentally prepared myself for the swap. (Also, I unplugged the PSU and hit my PC’s power button a few times to discharge the capacitors so I wouldn’t electrocute myself.) With that done, I unscrewed the PSU and, since I couldn’t be bothered unplugging all my components, I laid it flat atop the case’s support beams. A minute later, the S12’s warranty seal was irrevocably broken, and the hood housing its lone 12 cm fan was lying on my desk.

The old fan inside the PSU hood.

There was a problem, though: the fan was plugged into a two-pin connector, and the Scythe fan I had ordered had a three-pin connector. Most case fans out there use either four-pin connectors of the Molex type, like the ones you use to plug in older hard drives, or three-pin connectors with power, ground, and speed monitoring wires that plug straight into the motherboard. You can get three-pin to four-pin adapters quite easily, but there’s much less demand for two-pin adapters, and they’re very hard to find.

Luckily, I had read up on the subject beforehand and knew what to do. I made a note of the polarity (ground closest to the side, then power behind that) then used a small flathead screwdriver to pry off the two-pin plastic header, leaving the two pins it housed bare. I was then free to plug in the three-pin connector, leaving its yellow speed-monitoring cable plugged into nothing.

Prying out the 2-pin header.

Plugging in the new fan’s 3-pin header.

The fan plug is admittedly a little loose, since there’s nothing holding it in place. That said, the capacitor sitting behind it prevents it from slipping out completely, and it still feels somewhat securely in place. In hindsight, I probably should have used a touch of superglue to keep the connector in place, but I’m not particularly worried about it slipping off unless I throw the PSU down a flight of stairs—and then I’d have other things to worry about, like alarming the neighbors and having to gather scattered capacitors and circuit boards.

Once the new fan was in place, I used a cable tie to make sure the wires stayed out of the way of fan blades, and I closed the unit. Surprisingly, the hardest part of this adventure was getting the new fan mounted. Seasonic put some rubber grommets between the fan and fan grill to dampen vibration, and keeping those in place while I lowered the new fan down was a painstaking and frustrating experience. Nonetheless, everything eventually went back together just fine.

The new fan inside my PSU. You can tell it’s new ’cause it’s not covered with dust.

My work done, I hit my PC’s power button, and the system booted quite happily—and while making noticeably less noise than before. Evidently, the new fan is a good deal quieter than the old one was even before it started malfunctioning. (And yes, I checked to make sure it was actually running). Everything is still going strong after six hours, which suggests I didn’t break anything important during the maneuver.

Again, I must stress that sending the power supply back to its manufacturer is the safest course of action. You don’t want to risk zapping yourself or damaging your shiny PSU unless you know what you’re doing. With that said, you don’t have to part with a power supply that has a dying fan if you don’t want to, and you don’t necessarily have to do any soldering or heavy-duty stuff to get the job done—so long as your PSU fan isn’t hard-wired in, anyway.

Comments closed
    • FubbHead
    • 12 years ago

    A nice little insight to the everyday trials the typical techie puts himself through. 🙂

    • DASQ
    • 12 years ago

    I did sorta the same thing to an old thermaltake PSU.

    but instead, I adhered two additional large (old P3 slot 1 heatsinks that I cut down) heatsinks to the internals of the PSU, and placed the fan on the outside.

    The PSU now actually runs fine with the fan turned off, surprisingly.

    • dextrous
    • 12 years ago

    I kept reading waiting for a funny story or something. I guess I’m hardcore or something cuz I’ve performed this procedure at least a couple dozen times in the last decade. *shrug*

    If the fan is hardwired to the circuit board in the PSU, just run the connector for the fan out of the power supply with all the other power connectors and plug it into the motherboard/molex connector/whatever. Works great

    • DrCR
    • 12 years ago

    What’s ironic is I’m planning on going ahead and replacing the fan of whatever PSU I settle on for a new build in a few weeks. SPCR’s [url=] new testbed [/url] with a Seasonic S12-600 modded a Slip Stream 800rpm @ 5v (~400W) sounds really sweet config.


      • UberGerbil
      • 12 years ago

      Ironic? What are you, Alanis Morissette?

        • DrCR
        • 12 years ago


          • derFunkenstein
          • 12 years ago

          He means it’s not irony, it’s coincidence.

            • UberGerbil
            • 12 years ago

            Exactly — just like many examples in the song. It would be ironic if you had just attempted this mod and it had failed because you didn’t have a guide like this. It would be ironic if you had just done this mod and found a completely different way to do it that would have saved Cyril a bunch of time and effort. It would’ve been ironic if Cyril had done this mod and then discovered a receipt with a warranty that would’ve allowed him to RMA the thing — except he now couldn’t, because he’d modded it. That’s irony.

            But the fact that he gave you this guide right before you were going to do it? That’s a happy coincidence.

            • flip-mode
            • 12 years ago

            So irony = bad coincidence?

        • sigher
        • 12 years ago

        haha 🙂

    • JustAnEngineer
    • 12 years ago

    I have performed this modification a few times. I usually recommend against it for most folks because of the risk of electrocution or fire.

    The 2-pin vs. 3-pin issue is pretty simple when you’re working with Panaflo fans with swappable tails.

    • just brew it!
    • 12 years ago

    Fans really are the weak link in most modern PCs. It’s why minimizing the number of fans is one of my criteria when I select components for a system build. Fanless northbridge and video card count for a lot in my book.

    I’ve generally not had a lot of trouble with PSU fans; the fact that they tend to be larger diameter and lower RPM helps a lot. Sounds to me like the fan in your Seasonic was defective…

      • willyolio
      • 12 years ago

      yeah, my next build i’m attempting to go at it with only 1 fan for the entire system. the only one i couldn’t eliminate was the PSU. i’m hoping it’ll be quieter and closer to dust-free than anything i’ve ever tried. i’m also hoping it won’t overheat.

        • Flying Fox
        • 12 years ago

        Yes, and to go with a passive PSU means you need to keep your ambient low enough which is not always possible.

          • willyolio
          • 12 years ago

          it just requires a non-box to hold everything in, where convection currents actually have room to move. and off-the-shelf passive coolers aren’t enough either, since they’re designed to have a good amount of internal airflow already.

          i’m just glad i live in a temperate coastal city.

      • Jigar
      • 12 years ago

      Trust me, noise was never an issue for me before, but my new system has started making a lot of noise this days..

    • highlandr
    • 12 years ago

    I did something similar years back – my el cheapo PSU didn’t have internal venting in the right place, so I took it apart and drilled some holes directly over where my 300A resided.

    It is an adventure to crack that seal though – especially knowing that there are plenty of things in there that could give you a zap. Not something you do everyday.

    • UberGerbil
    • 12 years ago

    Nice little mod, even if it was prompted by a failure.

    Of course, the hardcore would’ve run a wire from the open plug to an available header on your motherboard, so you could monitor the speed of the PSU fan as well.

    (Wasn’t there a PSU with an internal USB port and software that allowed you to monitor PSU temp, fan speed, etc. Or am i imagining that?)

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