How Do I Test the Power Supply in My Computer?

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 he will probably tell you that the power supply is the most common piece of hardware to fail in a computer. In my experience, the power supply is very often the first thing to fail as a computer ages.


2 Ways to Test the Power Supply in a Computer

How to Test the Power Supply in Your Computer

You can test a power supply 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 ways of testing a power supply, so which one you choose is completely up to you.

Power supply in a PC
TimeStopper / Getty Images

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
  • The only tools needed are a screwdriver and a multimeter, both of which you likely already have. If you don't own a multimeter, you can usually find a basic one at any major retailer for around $30 USD.

  • Assuming you have a multimeter and screwdriver, you can test your power supply right now following the directions above.

What We Don't Like
  • It's manual! It's going to take a little work on your part to thoroughly test your power supply.

  • Testing a PSU manually can be dangerous if you're not very, very careful. See the warning at the bottom of the page for more information.

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

The instructions linked to the above are specific to the highly-rated Coolmax PS-228 ATX Power Supply Tester, but the general idea applies to nearly any tester you choose to purchase.

What We Like
  • It's automatic! Power supply testers 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.

  • Testing a power supply with a power supply tester is a safer than testing one manually. A power supply tester lets you stay a bit more removed from the electricity than with a multimeter test.

What We Don't Like
  • Chances are you don't have a power supply tester so you'll have to buy one. Depending on your choice of tester, you're probably looking to spend from around $10 to $40 USD.

  • Again, you probably don't have a power supply tester, meaning that you'll have to order one and wait until it shows up before you'll be able to test your power supply. That could mean that you live with a major computer problem longer than you'd like.

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! The image on this page is for illustration purposes only, not as a direct example of testing a PSU!

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