The great PSU fan swap of 2008


— 1:04 PM on February 27, 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.

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