How Do I Test the Power Supply in My Computer?

You can test the PSU yourself with a multimeter, or you can perform an automatic test

By
Tim Fisher
Photo of Tim Fisher, Lifewire GM and Writer
Tim Fisher
Senior Vice President & Group General Manager, Tech & Sustainability
  • Emporia State University

Tim Fisher has more than 30 years' of professional technology experience. He's been writing about tech for more than two decades and serves as the SVP and General Manager of Lifewire.

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Updated on November 21, 2022

Testing a power supply is an important step when troubleshooting many issues, most obviously when your computer is having trouble starting. However, a failing power supply can often be at the root of problems you might not expect, like random lockups, spontaneous reboots, and even some serious error messages.

Ask any computer repair professional, and they will probably tell you the power supply is the most common piece of hardware to fail in a computer. It's very often the first thing to fail as a computer ages.

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2 Ways to Test the Power Supply in a Computer

How to Test the Power Supply in Your Computer

You can test it yourself manually using a multimeter (method #1) or you can purchase a power supply tester to perform an automatic PSU test (method #2).

Both methods are equally effective, so which one you choose is completely up to you.

Here's some more information on how to test your power supply with each of these methods, and some help deciding which way is best for you:

Method #1: Test a Power Supply Manually With a Multimeter

What We Like

  • Requires only a screwdriver and multimeter.

What We Don't Like

  • It's manual.

  • Testing can be dangerous if you're not very, very careful.

Assuming you have a multimeter and screwdriver, you can test your power supply right now, following the directions above. If you don't own a multimeter, you can usually find a basic one at any major retailer for around $30.

It's going to take a little work on your part to thoroughly test your power supply. If you do decide to, be sure to see the warning at the bottom of this page for more information.

Method #2: Test a Power Supply Using a Power Supply Tester

What We Like

  • It's automatic.

  • It's safer.

What We Don't Like

  • You'll need to buy the power supply tester; chances are you don't already have one.

A power supply tester lets you stay a bit more removed from the electricity than with a multimeter test. Since they were invented because manual tests are manual and introduce human error, the results of a PSU test with a power supply tester unit is more conclusive.

Depending on your choice of tester, you're probably looking to spend from around $10 to $40 USD.

Those instructions are specific to the highly-rated Coolmax PS-228 ATX power supply tester, but the general idea applies to nearly any tester you use.

Take great care when testing a power supply, especially if you've chosen to test it manually. Both methods above involve working with a high voltage power supply while it's plugged in. If you're not extremely careful, you could electrocute yourself and/or damage your computer. Testing a power supply is a common troubleshooting step and can be done safely if you exercise common sense and follow directions exactly. Just be careful when doing so.

Did Your Power Supply Fail a Test?

Replace the power supply. That's right, just replace it, even if it's partially working.

It's never a safe idea to fix one yourself. If you insist on having your PSU repaired rather than replaced, then please seek the assistance of a professional repair person.

Do not open a power supply's cover under any circumstances!

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