How to Fix a Computer That Turns On and Then Off

What to do when your computer shuts off during the boot process

Is your computer turning off by itself immediately or at some point before the operating system loads? If so, you could be facing anything from an electrical short to a serious hardware problem.

Because there are several reasons that your PC might be shutting off by itself during the boot process, you must step through a logical troubleshooting process like the one we've described below.

If your computer is staying on, even if you don't see anything on the screen, see How to Fix a Computer That Won't Turn On for a more helpful troubleshooting guide.

How to Fix a Computer That Turns On and Then Off

This process could take minutes to hours, depending on why the computer turns off so quickly after being turned on.

  1. Troubleshoot the cause of the beep code, assuming you're lucky enough to hear one. A beep code will give you an excellent idea of exactly where to look for the cause of your computer turning off.

    If you don't fix the problem that way, you can always return here and continue troubleshooting with the more generic information below.

  2. Verify that the power supply voltage switch is set correctly. If the input voltage for the power supply doesn't match the correct setting for your country, your computer might not stay powered on.

    Chances are your computer wouldn't power on at all if this switch is wrong, but an incorrect power supply voltage might also cause your computer to turn off by itself.

  3. Make sure you're keeping the computer cool enough, or it might overheat to the point that it shuts down. Follow that link for easy tips anyone can follow to cool down their computer.

    Some computer cooling techniques for desktops require you to open your computer, but that's pretty easy to do.

  4. Check for causes of electrical shorts inside your computer. It's often the cause of the problem when the computer powers on for a second or two but then powers off completely.

    Inspect the inside of your computer for problems that cause shorting. If you don't take the time to troubleshoot this possibility thoroughly, you may end up missing a simple electrical short and performing costly hardware replacements later for no good reason.

  5. Test your power supply. Just because your computer came on for a few moments doesn't mean that the power supply unit in your computer is working correctly. The power supply tends to cause more problems than any other piece of hardware and is very often the cause of a computer turning off by itself.

    Replace your power supply if it fails any of your tests.

    If you end up replacing the PSU, keep the computer plugged in for at least five minutes before you try powering it on. This pause gives time for the CMOS battery to charge a little.

  6. Test the power button on the front of your computer's case. If the power button is shorting out or even just sticking to the case, it might be the reason your computer is turning off by itself.

    Replace the power button if it fails your testing or if you suspect it's not working correctly.

  7. Reseat everything inside your computer. Reseating will reestablish all the connections inside your computer, which may have wiggled loose over time.

    Try reseating the following and then see if your computer stays on:

    Unplug and reattach your keyboard and mouse as well. There's little chance that either one is the cause of this problem, but we shouldn't overlook them while we're reseating everything else.

  8. Reseat the CPU only if you suspect it might have come loose or wasn't installed correctly.

    We call this out separately only because the chance of a CPU coming loose is very slim and because installing one is a sensitive task. It isn't a big concern if you're careful, so don't worry!

  9. Clear CMOS to erase the BIOS memory and return its settings to their factory default levels. A BIOS misconfiguration could be why your PC won't start up normally.

    If reseating the battery doesn't fix the problem, consider replacing the CMOS battery.

  10. Start your PC with essential hardware only. The purpose here is to remove as much hardware as possible while still maintaining your computer's ability to power on.

    If your computer turns on, and stays on, with essential hardware only, proceed to Step 11.

    If your computer continues to turn off by itself, proceed to Step 12.

    This troubleshooting step is easy enough for anyone to complete, takes no special tools, and could give a lot of precious information. It isn't a step to skip if your computer is still shutting off by itself after following the steps above.

  11. Reinstall each piece of non-essential hardware, one component at a time, testing your computer after each installation.

    Since your PC powered on with only the essential hardware installed, those components are working correctly. It means that one of the devices you removed is causing your computer to turn off by itself. By installing each device back into your computer and testing after each installation, you'll eventually find the hardware that caused your problem.

    Replace the faulty hardware once you've identified it.

  12. Test your PC using a Power On Self Test card. If your computer continues to power off by itself with nothing but essential PC hardware installed, a POST card will help identify which piece of remaining hardware is to blame.

    If you don't already own and are unwilling to purchase a POST card, skip to Step 14.

  13. Replace each piece of essential hardware in your computer with a "known good" identical or equivalent spare piece of hardware, one component at a time, to determine which part of the hardware is causing your computer to shut off automatically. Then test after each hardware replacement to determine which device is faulty.

    Most average computer users don't have a collection of working spare computer parts at their disposal. Our advice is to revisit Step 12. A POST card is not expensive and is a much more reasonable approach than stocking spare computer parts.

  14. Finally, if all else fails, you'll likely need to seek professional help from a computer repair service or your computer manufacturer's technical support.

    If you're without a POST card and spare parts to swap in and out, you're left not knowing which piece of your essential computer hardware is faulty. In these cases, you have little option but to rely on individuals or companies with these resources.

  • Why does my PC screen keep turning on and off?

    If your monitor keeps turning off, it could be due to a faulty connection with your PC, or it could be overheating. Check the cables, clean your monitor, and take steps to keep it cool.

  • How do I turn off unnecessary startup apps on my PC?

    To change startup programs in Windows, open Task Manager and go to the Startup tab. Next, select the Status column to sort the applications into Disabled and Enabled. To disable any application, right-click anywhere in its row and select Disable.

  • How do I remotely turn my PC power on and off?

    First, log in to your Windows PC remotely. Then, use the Shutdown command to turn it off.

  • How do I fix it when my PC turns on but displays nothing?

    If your PC turns on but displays nothing, power off your computer by holding down the power button for 3-5 seconds. After the power is completely off, turn on your PC to see if it will boot normally. If not, verify that the power supply voltage switch is set correctly and check for signs of electrical shorts.

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