Power Supply Fan Failure Warning: Fix It Before Your PSU Dies
Your PC warns the PSU fan isn't spinning. This usually happens during boot or under load. Here's how to confirm the failure and fix it.
What triggers this error
You're booting up your desktop, and instead of the normal Windows logo, you get a black screen with a message like "Power Supply Fan Failure" or "PSU Fan Error". Sometimes it's a single long beep followed by two short beeps. This tends to happen right after you've moved your PC, cleaned it, or replaced a component. It can also show up randomly on older systems—especially with Corsair RMx series or EVGA SuperNOVA units that have semi-passive fan modes. The motherboard's hardware monitor detects the fan isn't spinning at POST (power-on self-test) and flags it as a critical error.
Why it happens
The motherboard expects a tachometer signal from the PSU fan header. If that signal is absent—either because the fan is physically stuck, dead, or the connector inside the PSU came loose—the system halts. This isn't a false alarm in most cases: your PSU relies on that fan to keep its internal components cool. Without it, you risk blowing a capacitor or melting a solder joint under load. The one exception is PSUs with a semi-passive mode (fanless below a certain wattage). Those won't spin the fan until the power draw hits around 20-30%, so the motherboard might panic even though nothing's wrong.
Fix it in 5 steps
- Check if the PSU fan is actually spinning — Power on your PC and look at the back of the case. If the fan isn't turning, shut down immediately. If it is turning, you've got a false positive.
- Disable the warning in BIOS — Restart and mash the Del or F2 key. Go to the Monitor or Health tab. Look for Chassis Fan 1 or Power Supply Fan and set it to Ignore or N/A. This only works if the fan is actually spinning but the signal is flaky.
- Try a different fan header — If your motherboard has a dedicated PSU fan header, you can often plug the PSU fan into a regular chassis fan header. Open the PSU (careful—capacitors hold charge), locate the fan cable, and move it to a free header. This is an advanced step; don't attempt it if you're uncomfortable with electronics.
- Replace the PSU fan — Order a replacement fan (same size, usually 120mm or 140mm, and same connector type). Remove the old fan, solder or splice the new one's wires to the original connector, and reassemble. Use a fan with the same voltage (12V) and similar amp rating.
- Replace the entire power supply — If the fan is truly dead and you don't want to crack the PSU open, buy a new unit. A failure like this often means other components inside are aging. Don't risk your $500 GPU over a $100 PSU.
What to check if it still fails
If you've done the steps above and the warning persists, double-check these things:
- Dust buildup — A thick layer of dust can stop the fan dead. Blow it out with compressed air. Don't use a vacuum—static electricity kills electronics.
- Obstructions — A stray cable tie or case wire can wedge against the fan blades. Look inside the PSU vents.
- Semi-passive mode confusion — Some PSUs (like the Seasonic Focus series) have a switch to toggle the fanless mode. If it's on, the fan won't spin until high load. Turn that switch off during boot.
- Motherboard BIOS update — A rare bug in early UEFI revisions (common on ASUS Z390 boards) misreads the fan signal. Update the BIOS to the latest version.
If none of that works, swap the PSU with a known-good unit. If the error goes away, it's time for a new power supply. If it doesn't, the motherboard's fan header might be fried—try a different header or a USB-powered fan controller.
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