To test a PSU with a paperclip, you unplug everything except the 24-pin cable, bridge the green PS_ON wire (pin 16) to a neighboring black ground wire (pin 15 or 17) with a bent paperclip, then switch the PSU on: if the fan spins, the unit can start, but this does not prove it is healthy under load.
What the Paperclip Test Does and Does Not Tell You
An ATX power supply stays off until the motherboard pulls the green PS_ON wire to ground. The paperclip does the same job by hand. If the fan spins and the unit stays on, the PSU’s standby circuit and basic startup are working. That is useful when a PC will not turn on and you need to separate a dead PSU from a faulty motherboard, power button or other part.
It does not measure voltage accuracy, ripple or behavior under load. A power supply can spin its fan and still deliver unstable voltage when a graphics card draws heavy current. For that, builders use a dedicated PSU tester or a multimeter, or they swap in a known-good PSU. If the unit passes the paperclip test but the PC still has problems, the cause may lie elsewhere, such as the motherboard, the case power switch or the CMOS.
Safety First
- Never open the power supply case. Capacitors inside can hold a dangerous charge even when unplugged.
- Never run the test with the PSU connected to a motherboard, graphics card or drives.
- Only short the PS_ON wire and a ground wire. Bridging any other pins can damage the PSU or components.
- Place the PSU on a stable, non-conductive surface and keep your hands away from the fan.
- If you are unsure, stop and ask a technician, or contact the PSU maker, especially if the unit is under warranty.
What You Need
- A standard paperclip, or a purpose-made jumper plug.
- The power supply, with its AC power cord.
- Optionally, a PSU tester or multimeter for follow-up checks.
Step-by-Step Instructions
- Shut down and unplug. Turn the PSU’s rear switch to the off position (marked 0) and unplug the AC cord from the wall.
- Disconnect the PSU from the system. Remove the 24-pin cable from the motherboard and unplug every other PSU cable from the motherboard, graphics card and drives. Some guides leave a load such as a drive connected; the safest approach is to remove everything and connect only the AC cord.
- Find the 24-pin connector. Hold it with the latch side facing up. Pin 16 is the green wire. The black wires on either side, pins 15 and 17, are grounds (COM). Pins 16 and 17 are the 4th and 5th positions along the latch row in the layout used by one maker’s guide, but the wire colors are the most reliable cue.
- Bend the paperclip into a U. Make sure it is straight, clean and fits snugly.
- Insert the clip. Push one end into the green wire’s socket and the other into an adjacent black wire’s socket. It should hold itself in place without touching other pins.
- Reconnect AC power. Plug in the AC cord, then switch the PSU rear switch to on (I).
- Watch the result. The fan should start spinning and, on some models, a light may turn on.
- Power down. Switch the PSU off, unplug the AC cord, wait a minute, then remove the paperclip.
How to Read the Result
| What you see | Likely meaning | Next step |
|---|---|---|
| Fan spins and stays on | The PSU can start | Check rails under load with a tester or multimeter, or look at other components |
| Fan does not spin | PSU may be faulty, the clip may be in the wrong pins, or the wall outlet may be dead | Recheck pins and the outlet, try another cable, then contact the maker |
| Fan spins briefly then stops | Protection circuit may be tripping, or no load is present | Try again once; if it repeats, stop using the unit |
| Fan spins but PC still fails | Problem may be elsewhere | Test with a known-good PSU or inspect motherboard, RAM and power button |
| Burning smell or sparks | Serious fault | Switch off at once and do not use the PSU |
Common Mistakes
- Using the wrong pins. Always confirm the green wire first.
- Leaving the PSU connected to parts. This risks damage if anything is faulty.
- Treating the test as a full health check. It only confirms startup.
- Testing an old, swollen or damaged unit. Do not power up a PSU with visible damage.
- Forgetting the rear switch. A PSU left off at the switch will never spin.
When Not to Do It
Skip the paperclip test if the PSU has visible damage, a burning smell, bulging, exposed wiring or liquid exposure. Skip it if the unit is still under warranty and the maker asks you to return it untouched, if you are not comfortable working near mains power, or if you can swap in a known-good PSU instead. Some modern units, including those with unusual connectors, have maker-specific test advice, so read the manual first.
Better Ways to Confirm a PSU Problem
A dedicated PSU tester plugs into the connectors and shows the rails on a screen, which is easier than using a paperclip. A multimeter can measure rails on the back of connectors, but it needs care and knowledge of which pins to probe. The most dependable check is swapping in a known-good power supply of adequate wattage, which tests the whole system under real load.
Signs a PSU May Be Failing
Before testing, note the symptoms that point toward the power supply: random shutdowns under load, a PC that will not start with no lights, a burning smell, buzzing or coil whine that is new, or restarts when the graphics card gets busy. These signs are not proof, since RAM, motherboard and GPU faults can look similar. If several symptoms appear together, a replacement PSU from a reputable maker is a reasonable next step. If the unit is still in warranty, contact the maker and describe what you saw. Do not attempt internal repairs, and dispose of a failed unit through an electronics recycling point.
Frequently Asked Questions
Which pins do I bridge for the paperclip test?
Bridge the green wire (pin 16, PS_ON) to a black ground wire next to it, commonly pin 15 or 17. Most guides use pin 17.
Is the paperclip test safe?
It is considered low risk when done correctly with everything disconnected, but it involves mains power at the PSU. Never open the unit and never use the wrong pins.
Can I run the test with the PSU connected to the motherboard?
No. Disconnect it from all components first. The test is meant to check the PSU alone.
My PSU fan spins. Does that mean it is fine?
It means the unit starts. It does not prove voltages are stable under load. If the PC still crashes or will not start, use a tester or swap in a known-good PSU.
Can a modular PSU be tested the same way?
Yes, using the 24-pin connector that plugs into the PSU, but modular cables are not interchangeable between brands. Use only the cable that came with your unit and follow the maker’s instructions.
