If your PC suddenly shuts down, won’t turn on, or you suspect a hardware issue, learning how to test a power supply is one of the best first steps. This guide will show you how to test a PC power supply at home—even if you’ve never handled computer parts before.
Testing your power supply unit (PSU) may sound tricky, but don’t worry! With easy instructions and a few simple tools, you’ll be checking your PSU like a pro in no time.
Let’s dive in!
Why Is Testing Your Power Supply Important?
Before you learn how to test your power supply, let’s talk about why it matters.
Your PSU is like the heart of your computer—it sends power to every part of your PC. If it fails, things can go wrong quickly.
Problems a bad PSU might cause:
- Random shutdowns or restarts
- A computer that won’t turn on
- Blue screen (BSOD) errors
- Strange beeping sounds
- Damage to your motherboard, GPU, or storage components
So, if your computer is acting weird—or not turning on at all—testing your power supply is a smart place to start.
What You Need to Test a PC Power Supply
Here’s what you’ll need to get started:
- A metal paperclip or a PSU tester
- A digital multimeter (for checking voltages precisely)
- Phillips screwdriver (most common type)
- Anti-static wrist strap (optional, but helps prevent part damage)
- Your computer’s PSU
Pro Tip: Use a flashlight to see inside small areas if you’re working inside a case.
Always Put Safety First
⚠️ Power supplies can hold dangerous electricity—even when unplugged—so take precaution!
✅ Unplug your computer from power
✅ Press the power button for at least 10 seconds after unplugging (this discharges any stored energy)
✅ Work on a surface without carpet or static
✅ NEVER open the metal casing of the power supply itself
Now that you’re working safely, let’s move to the fun part—testing!
Method 1: Paperclip Test – Quick & Easy Power Check
The “paperclip test” is a fast way to see if your PSU can power on. This won’t tell you if the voltages are correct—but it tells you the PSU turns on.
🛠️ What You Need: A paperclip.
🧪 Follow These Steps:
- Make sure your PSU is unplugged.
- Disconnect all PSU cables from your motherboard and other devices.
- Find the 24-pin ATX main power connector (it’s the biggest plug).
- Bend a paperclip into a U-shape.
- Insert one end into the green wire slot (Pin 16), and the other end into any black wire slot (Pin 15 or 17).
- Plug the PSU into the wall and flip it ON.
- Watch: Does the fan on the PSU turn on?
🟢 If yes: The PSU at least turns on—which is a good sign.
🔴 If no: The PSU could be dead, or the fan itself may be broken.
⛔ Warning: Do not touch metal ends of the paperclip or connector area when plugged in.
This simple method helps beginners see if a PSU works at a basic level. For more detailed testing, let’s learn how to test power supply voltage using a multimeter.
Method 2: How to Test a Power Supply with a Multimeter
A multimeter allows you to measure the voltages your PSU provides. This tells you if it’s giving your parts the right amount of power.
Voltage rails to test:
- Yellow wires = +12V
- Red wires = +5V
- Orange wires = +3.3V
- Black wires = Ground (always negative)
- Green = Power on
- Blue = -12V
- Purple = +5V standby
🛠️ What You Need: A digital multimeter + PAPERCLIP for the power-on bypass.
🧪 Step-by-Step Guide:
- Turn off your PC and unplug the PSU.
- Unplug all PSU wires from your hardware.
- Set your multimeter dial to 20V DC (volts direct current).
- Use the paperclip method above to jump the green and black wire on the 24-pin connector.
- Plug in the PSU and turn it ON.
- Touch the black probe to a black (ground) wire and the red probe to:
- Yellow wire = +12V
- Red wire = +5V
- Orange wire = +3.3V
💡 What to Look For:
- +12V rail: Value should be between 11.4V and 12.6V
- +5V rail: Value should be between 4.75V and 5.25V
- +3.3V rail: Value should be between 3.14V and 3.47V
📉 If any voltages are outside these limits, the PSU is failing and must be replaced.
Multimeters are very accurate, and once you get the hang of it, they’re simple to use.
Method 3: Using a PSU Tester – Fastest & Easiest
A PSU tester is the most beginner-friendly tool if you’re unsure about using a multimeter.
🛠️ What You Need: A PSU tester (can be found online for $10–$20)
🧪 How to Use It:
- Plug your 24-pin cable into the PSU tester.
- Plug in additional connectors like CPU (4/8-pin) or PCIe cables if your tester has those slots.
- Connect the PSU to power and switch it ON.
- The screen shows voltage results—and some testers beep if there’s a problem.
✅ All voltages in the correct range? You’re good!
⛔ Tester beeping or error message? Time for a new PSU.
If you plant to build more PCs or troubleshoot often, investing in a PSU tester is worth it.
Signs of a Failing PSU
Still not sure it’s your power supply? Watch for these clues:
- PC doesn’t power on at all
- Computer freezes, reboots randomly
- Fans spin for a second, then stop
- Beeping or electrical buzzing sounds
- Burning smell or visible scorch marks
- Crashes during gaming or rendering
If you see any of these, you should test your PSU right away.
What to Do If Your Power Supply Fails?
If your PSU fails ANY test—especially voltage checks—it’s time to replace it. Do not risk using a bad PSU.
🛒 When buying a new power supply:
- Choose a known brand (Corsair, Seasonic, EVGA, etc.)
- Match wattage to your needs (use an online PSU calculator)
- Look for 80+ efficiency certification
- Modular or semi-modular options make cable management easier
📌 Important: Don’t overspend, but don’t go too cheap either. A quality PSU protects your expensive hardware.
Bonus Tips: Make Your PSU Last Longer
Here are a few things you can do to keep your PSU in good condition:
🌀 Clean dust out often—especially around fans
🔌 Use surge protectors or a UPS to prevent voltage spikes
🌡️ Keep your computer cool with good airflow
📆 Consider replacing the PSU every 5–7 years, especially for heavily used systems
Final Thoughts: You’re Now a Power Supply Pro 💪
Now you know how to test a power supply like a pro—in three different ways! Whether you use a paperclip, a multimeter, or a PSU tester, you’re taking an important step toward diagnosing issues and keeping your PC healthy.
Remember:
- Start simple with the paperclip test
- Use a multimeter to check voltage accuracy
- A PSU tester makes things super easy if you don’t want to handle probes
Whether you’re fixing problems or building a new rig, power supply testing is an essential skill.
🔧 Got questions? Leave a comment!
🖥️ Tested your PSU? Share your voltage results!
💡 Found this helpful? Bookmark this page or share it with a friend who’s also into PC building.
Happy PC building 🚀