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How to Test a Power Supply With the Paperclip Test
Short answer: The paperclip test checks whether a power supply can switch on by itself, outside the PC. Unplug its cables from the motherboard and graphics card, bend a paperclip into a U and bridge the 4th and 5th pins on the clip side of the 24-pin cable. Turn it on. If the PSU fan spins, it can power on.
When a PC shows no sign of life at all, the power supply is one of the main suspects. This test takes about five minutes and tells you whether the PSU can turn on, with the motherboard and everything else out of the picture.
Before you start, rule out the simple stuff: the wall outlet, the power cord and the switch on the back of the PSU. Our guide to what to do when your PC won't turn on covers those checks.
Bought an NZXT prebuilt PC that's still under warranty? Skip this test and contact NZXT Support instead. This guide is for PCs you built yourself.
What you need
- A metal paperclip or a short piece of stiff wire
- Scissors, wire cutters or side cutters
Some power supplies come with a jumper in the box for exactly this test. If yours did, use that instead.
Step 1: Disconnect the power supply
- Switch the PSU off at the back (the O position) and unplug its power cord from the wall.
- Take off the side panels.
- Unplug the 24-pin cable from the motherboard. Press down on its clip as you pull.
- Unplug the CPU power cable at the top of the motherboard and the graphics card's power cables the same way.
On a modular power supply, leave the 24-pin cable plugged in at the PSU end. That's the cable you're testing through.
Step 2: Make the jumper
Cut the inner loop out of the paperclip so you're left with a U shape. If the paperclip has a plastic or rubber coating, strip it off the ends so bare metal touches the pins.
Step 3: Bridge the right two pins
Hold the 24-pin connector with its clip facing up and the pin holes facing you. If your cable splits into a 20-pin and a 4-pin section, keep the 4-pin section on the right. In the row of pins on the clip side, count from the left and push one end of the jumper into the 4th pin and the other into the 5th.
On a cable with colored wires, the 4th pin is the green wire, the power-on signal. The 5th is the black ground wire next to it. Many modular cables are all black, so count the pins rather than looking for green.
Step 4: Turn off any fan-stop mode
Many power supplies stop their fan at low load to stay quiet. With nothing connected, that would make a working PSU look dead. If yours has a switch labeled Eco Mode, Quiet Mode or Zero RPM Mode, usually next to the power switch, turn it off. Your PSU's manual shows how.
Step 5: Power it on and watch the fan
- Make sure the jumper is the only thing touching the connector and no loose cable ends are resting on metal. Once the PSU is on, every cable on it is live, so keep your hands off them.
- Plug the power cord back in and flip the PSU switch to the on position (I).
- Look at the PSU fan rather than listening for it. If the PSU sits behind a dust filter, take the filter off to get a clear view.
- When you're done, switch off, unplug the cord and then remove the jumper.
| Result | What it means |
|---|---|
| Fan spins | The PSU can turn on, which rules out a dead PSU. It can still fail under load, as the FAQ below explains. |
| Fan doesn't spin | The PSU isn't getting power or can't respond to the power-on signal. Recheck the outlet, cord, switch and fan-stop mode. If it still won't spin, the PSU has likely failed. |
Frequently asked questions
Is the paperclip test safe?
Yes, if you follow the order above. Unplug the PSU's cables from the motherboard and graphics card first. Insert and remove the jumper only while the PSU is switched off and unplugged. Once it's on, every cable on the PSU is live, so keep loose connectors away from metal and don't touch any of them until you've switched off and unplugged.
My PSU passed. Does that mean it's working fine?
It means it can turn on. This is a power-on test, not a load test, so a PSU that shuts off under a heavy gaming load can still pass. If your PC turns off mid-game, our guide to why a PC randomly shuts down covers what to check next.
The fan didn't spin. Is my PSU dead?
Probably, but rule out the easy causes first: a dead outlet, a loose cord, the switch still at O or a fan-stop mode left on. Also check both ends of the jumper are fully in the pins. If it still won't start, replace the power supply or make a warranty claim with its maker.
All my PSU cable wires are black. Which pins do I use?
The same two. Clip facing up, pin holes facing you and any separate 4-pin section on the right. Count along the clip-side row from the left and bridge the 4th and 5th pins. Wire color doesn't matter. Pin position does.
Do I need to take the PSU out of the case?
No. It can stay mounted. You only need to unplug its cables from the motherboard and graphics card so they don't power up during the test.
My PSU passed but the PC still won't turn on. What now?
Work through the rest of the system: RAM, the graphics card, the boot drive and the CPU and 24-pin power connections. Our PC won't turn on guide goes through them in order. Your motherboard debug LEDs can point you to the right part.
Need a hand?
If the test points to an NZXT power supply, contact NZXT Support with the result, your proof of purchase and the PSU's serial number. It speeds up any warranty claim.
