Besides a few innovative open-to-air case designs, an overwhelming majority of PC cases still rely on case fans to move air through the case and over warm components, such as capacitors. Similarly, CPU coolers also use the same fans optimized for static pressure to push air through radiator fins or around heat pipes and heatsinks. With the exception of a few air coolers that rely on the airflow in the case alone, PC component design is now standardized to use 120 or 140mm fans in most mini to full-tower chassis.
Replacing these fans is easy too, but knowing when yours are giving out can prevent a domino effect that leads to degraded system performance or eventual component failure if left unattended for long. We’ve all tried to extend the service life of fans with gentle percussive maintenance, but there are a few signs I’ve learned to watch out for. They are indicative of the eventual fan failure that looms, and catching the signs early should save you money in the long term, since fans are among the cheapest PC components.
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6 mistakes you’re making when buying new case fans for your PC
Table of Contents
Buying new case fans is a bit more complicated than you’d think
5
Slapping that rattle away won’t help
Tick, tick, boom!
Usually, the first sign of fans dying comes through an audible ticking or grinding noise from the fan, especially when you boot the PC after an extended cooldown. The root cause lies in the primary shaft of the fan becoming slightly misaligned with the bearing housing, which is sufficient for the fan blades to touch surrounding cables, grilles, or the mounting frame of the fan itself.
Quite like the wheel bearings of your vehicle and most things that spin, the bearings in a PC fan are mechanical components prone to wear. The wear is gradual, but guaranteed, irrespective of the type of bearing your fans are equipped with. Some designs, like fluid dynamic bearings, offer a longer usable lifespan (represented as MTBF or mean time between failures in engineering speak) than simpler and oftentimes cheaper sleeve bearings. However, they all fail the same way — it starts with a slight ticking, then a rattle, and that aggravates into a constant grinding noise.
I’ve used this method to identify fans that are nearing their end of life, but gently slapping them seems to work. That only temporarily solves the problem, though. I should warn you that sometimes the ticking sound can come from an actual obstruction to the fan blades, such as cable ties, labels for stray cables, and even loose or over-tightened mounting hardware. In rare cases, a poorly designed or overworked air cooler’s CPU heatpipes may cause cheap plastic fan frames to warp. If you dodge all these false positives and the ticking doesn’t stop, it’s time to scope out some new fans.
4
Louder operation
Listen closely for this one
Closely tied to the previous method of spotting case fans on their deathbed, sometimes you’ll just notice a general increase in the sound a spinning fan makes, even while the RPM stays constant. The gradual changes in loudness may be imperceptible, but signify caution, especially if your case uses silent fans or your fan curve is optimized for silent operation.
I tend to notice abnormally loud operations when I return to my computer on Mondays, or after a short vacation. In any instance, the loudness usually stems from mechanical wear of the fan’s bearing, which we mentioned earlier. While the specific reason, such as loss of dynamic lubrication or slight misalignment, might be challenging to pinpoint, it is often an endeavor of futility, too, since PC fans aren’t user-repairable, anyway. If you hear them getting louder without specific instructions from PWM signals to spin faster, chances are your fan is on its way out.
A forum discussing this issue explains that this mode of failure starts with noisy operation only when you boot your PC and the fan shaft is loose in its sleeve. Prolonged operation of the fan reduces the clearance for wobble, eliminating the associated noise as well. Eventually, the clearances get worse, and the noise doesn’t reduce until the fan stops working.
3
Dying LEDs
This one’s for all the RGB fans
While it isn’t uncommon to come across mechanical telltale signs of impending doom for your case fans, there are changes you’ll see their end coming before you hear them. Unlike thunder and lightning, it’s not because light travels faster than sound, but simply due to some cheap LEDs that don’t last as long as the fan bearings. I’ve had addressable RGB LEDs fail on me while the fans kept spinning. That said, generalizing failure rates and correlating it to service life is incorrect.
As such, there’s a chance your LEDs will conk off sooner than the fan’s motor. In a build where RGB plays an important role in maintaining the aesthetics, LED failure alone can warrant fan replacement. However, I prefer switching off the LEDs on the dying fan via software, or just unplugging its RGB header and moving it to a different position in the case, where it won’t be as unsightly. While the potential risks of running case fans with non-functional LEDs aren’t documented in detail, I suppose the circuitry that powers and controls lighting is independent of the fan’s motor circuit.
2
Spinning slower than desired
Failure is nigh
Right alongside noisy operation, fans spinning slower than they’re supposed to is a guaranteed sign that it will not last much longer. Presuming that most case or cooler fans in your system use PWM control through the standardized four-pin header, I have found fans spinning visibly slower than others, and it’s a dead giveaway of the doom to come. However, diagnosis isn’t straightforward. You’ll see the problematic fan posting a slower RPM than others in the BIOS, but try ruling out the involvement of incorrect fan curve settings before proceeding. To know for sure, you can hook the fan up to your PSU directly and check for abnormal noise, vibration, or slowdowns before taking a call.
As for slightly older or basic fans that use Molex or three-pin connectors, slowdowns may be because of poor power supply or the fan’s inability to use the supplied voltage. It’s worth noting that while these fans should maintain a steady speed since they lack digital speed control, many motherboard brands resort to voltage manipulation for three-pin fan headers, so you can tweak them to match the fan curves approximately with other fans. Ensure you disable this feature in the BIOS during troubleshooting to avoid discarding a good fan outright.
1
Fans that just won’t switch on
Dead on arrival
I’ve had at least one of those awful days when I reached for my computer’s power button and a fan or two just didn’t spin up. Their LEDs lit up, but the fan remained immobile, and I didn’t encounter any of the aforementioned symptoms in the days leading up to this situation. If you’ve just finished working on your PC, be it routine maintenance or something more advanced like re-pasting the CPU, there’s a good chance you forgot to plug the fan into the corresponding motherboard header or daisy chain. Unlike CPU and GPU power connectors, fan headers don’t have locking pins, so they’re easy to unplug accidentally when switching orientation or disassembling radiators for cleaning. While you’re at it, check for physical obstructions in the fan like pet hair balled up around the main shaft.
In my case, the fan didn’t power on because of undisclosed liquid damage from the day prior. Once the traces evaporate, liquid spills inside your case can be near-impossible to identify and locate. Before you jump to conclusions or fear the worst for a dead fan in your build, visit the BIOS to ensure the Zero RPM or Quiet mode is disabled for the affected headers. For obvious reasons, I wouldn’t advise hitting your PC with an intensive load like a benchmark, hoping to get the fans to spin up. That said, you can try pinpointing the problem with the case fan by hooking it up to another motherboard header or your PSU directly and checking if it works.
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Thankfully, replacing dying fans is cheap
While most PC components can burn a hole in your pocket when it’s time to replace, case and cooler fans are among the cheapest components alongside budget cabinets, RAM, and peripherals. I’m confident I saved hours of heartache from damaged or overheated PC components because I paid attention to how my case fans sound, and when they stop working. I’d only suggest you do the same to reduce the risk of costlier repairs that may prove penny-wise and pound-foolish. Keeping your PC running cool affects the performance and longevity of other components, and like most things subject to mechanical wear, fans are, in part, consumables.
