How to Check Power Supply on a PC

Learning how to check your power supply on your pc is essential when looking to upgrade other components like your RAM or graphics card. Moreover, if you don’t have enough power to run all the parts of your computer, then you will experience constant catastrophic system failures and crashes.

To make sure that your computer’s power supply is up to the task, whether it’s for work or pleasure, you need to learn how to check it.

To test the power supply on a PC, you can use a paper clip to check whether it turns on, or a power supply testing unit to get a more accurate diagnosis.

If you want to know what PSU you have on your computer, you will have to find the details on the box it came in, search your PC’s specs online, or check the power supply’s label.

Read on to discover all the different methods to check the power supply on a PC!

Why Would I Need to Check the Power Supply Unit on My PC?

How to Check Power Supply on a PC

One of the main reasons why you might need to check your PSU is because your might be experiencing certain problems with your PC. In fact, many skilled PC technicians know to look first at the power supply unit when diagnosing PC hardware problems such as:

  • The PC not powering on at all.
  • System failures during the boot-up process.
  • Spontaneous restarts while using the PC.
  • Noisy fans.
  • Fans and hard drives not spinning.
  • Overheating.
  • Errors related to system memory.
  • Recurring Blue Screen of Death (BSOD).

Other reasons to check your PSU include adding new components like a graphics card or RAM, and overclocking them.

In the following sections, we’re going to teach you how to troubleshoot or check the power supply on a PC, depending on what your purposes are.

How to Test Power Supply on PC

Power Supply on a PC

Let’s start with two ways of testing the PSU on your PC to discover whether your computer problems are due to a faulty power supply.

Use a paper clip

Yes, believe it or not, you can use a regular paper clip to help test your power supply. This office device can be used to “trick” your PSU into thinking it has been turned on.

Just find a paper clip, straighten it, bend it into a “U” shape, and follow these steps:

  1. Shut down your computer, flip the power switch on the back of the PSU, and unplug it from the outlet.
  2. Open your computer case, and take a look at all the components that are connected to the PSU. Take note of where everything is plugged into (you might want to take a picture of it), and disconnect the power supply cables from all of the components.
  3. Locate the 20/24 Pin connector. It’s usually the largest connector for the power supply that attaches to the motherboard.
  4. Find the green pin and a black pin (pins 15 & 16). The green pin will be easy to find because there’s only one. As for the black pin, go for a neighboring one.
  5. Insert the ends of your handmade paperclip tester into each of the pins.
  6. Plug the PSU back into the outlet, and flip the switch on the back again.
  7. Check whether the fan is moving. If it does, then the power supply is working. Otherwise, you need to double-check your pins (remember to unplug the PSU) and try again. If the fans still don’t move, then your power supply is most likely dead.

The paperclip test will only tell you whether the power supply turning on. If you want to know whether it’s functioning and outputting correctly, you need to perform the next test.

Test the output

Power Supply Output

If your computer can load the OS, then the easiest way to check your power supply’s output is through software. One option is to use SpeedFan, a freeware program that monitors voltages, fan speeds, and temperatures.

However, if your PC doesn’t work, you will need a power supply testing unit. This is what you will need to do to test the output of your PSU:

  1. Shut down your computer. Unplug the power supply from the outlet, and flip the power switch on the back of the power supply. Open the PC’s case, make note of where everything is plugged into (you might want to take a picture of it), and disconnect all of the components from the power supply.
  2. Locate the 20/24 Pin connector. It’s usually the largest connector for the power supply that attaches to the motherboard.
  3. Connect the power supply testing unit to the 20/24 pin connector, plug the PSU back into the outlet and turn it on.
  4. Check the voltages, and look for the following measurements:
  5. +3.3 VDC
  6. +5 VDC
  7. +12 VDC
  8. -12 VDC
  1. Make sure that the voltages are within normal, accepted tolerances: the +3.3, +5, and +12 can be within +/- 5%, whereas the -12 can vary +/- 10%. Any readings outside of that range mean that the power supply is defective and should be replaced.
  2. Test the other connectors one by one. Remember to unplug and turn off the PSU between each test.

Reassemble your computer once the testing is done, ensuring that all the connectors are properly attached. If you’re still having computer errors despite the PSU passing the tests, try moving on to other troubleshooting steps.

How to Check What Power Supply You Have on Your PC

If you want to know the model of your current PSU to see whether it’s compatible with any new components you want to add to your PC, you can use any of the following methods.

Find out the power supply details on its box

If you’re like us and save the boxes or packages of everything you buy, then you’re in luck! The box of your power supply unit will surely have the model, wattage, and other specifications detailed on it. Moreover, there are PSU that come with a user manual that you can read to find out more about this component.

Checking the PSU’s box is certainly the easiest way to find out any details of your power supply. Don’t worry if you’ve thrown it away, there are still two other options you can try.

Search for PC specs on the manufacturer’s website

Computers that are prebuilt by a specific manufacturer will have a product page on the manufacturer’s official website. Just look it up on Google, search for the computer model number you own and read through the specs until you find the PSU’s wattage.

If you don’t know who the manufacturer is, search your PC’s model on Google, and you will certainly find the wattage within the first few search results. We recommend checking at least 3 search results and comparing them to ensure there’s no discrepancy.

Check the PSU label

The sure-fire way to check power supply on a PC is by reading the PSU label. All power supply manufacturers are required to include a sticker with the power rating on the product. So, there will always be a label sticker or printed layout of the power source model number, wattage, and other specifications on a PSU.

The downside is that you will have to open the case of your PC and remove about four screws to take your power supply out of your computer.

However, it’s relatively easy to do. Grab a No. 2 midrange size Phillips head screwdriver and follow these instructions:

  1. Power your PC down. Yes, the proper way. Hit “Start” or press the Windows key, then “Power,” and finally “Shut Down.” Unplug the computer from the power source once it’s off.
  2. Open the PC’s case. Depending on the model of the computer, you will need to either unclip the case or remove around two to eight screws.
  3. Locate the PSU. You will find it near the port for the computer’s power cord, the one you unplugged in the first step.
  4. Inspect the power supply to find the label and any pertinent information on it.

You should be able to see the max output (measured in watts) and efficiency rating easily, but if you don’t, try to find the PSU’s model name to search for it on Google.

Frequently Asked Questions

Which plugs do I test on my power supply?

You should test all of them because a functional power supply needs to have all its plugs working correctly. So, check the SATA plug, the Molex plug, the ATX plug, the video power card, and whatever other plugs your PSU has.

How do I tell if my power supply is bad?

One of the most common giveaways of a bad power supply is your PC turning off continuously while running it. You will need to run some of the tests we’ve mentioned in this article to confirm whether your PSU is bad.

What do you think about non-branded PSUs?

Honestly, most non-branded power supplies are highly inadequate and can easily damage your PC components. Saving a few bucks is not worth the risk in this case.


Checking the power supply on a PC is not as easy as checking RAM speed because there’s no connection between the PSU and the motherboard. You have to physically examine the component to find the information you need.

Luckily, we’ve provided several ways you can do this, together with clear instructions that will help you run the different tests efficiently.

All that’s left now is for you to discover whether your PSU is the source of your computer’s issues.

Liam Weissman

A lover of MacBook Air and the Dell XPS line of laptops, Liam has been researching and writing as a guest blogger for numerous websites for over 10 years. Now, he blogs about tech trends, PCs, laptops, gadgets, and other emerging gadgets on

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