Hardware Software Windows

Why does my PC turn off by itself?

Frustrated computer user
A real turn off: find out why your PC is randomly switching off

Few things rile a user more than a dead computer. Especially if the blessed thing seemed to work perfectly just a few moments earlier. If you’re arrived here, flustered, frustrated and wondering why your PC turns off by itself, then we’ve got a few suggestions for you.

What caused my PC to turn off by itself?

Sudden power loss can often be the sign of a severe problem with your computer, but probably one which is fixable. Software faults usually trigger a Blue Screen of Death before a crash, so an unexpected shutdown is probably hardware related. Or, at least, something which is causing functional hardware to fail. Like heat.

Signs a PC is overheating

Have you ever considered that your PC can suffer from heatstroke? It’s true. Unless it gets adequate airflow, or an alternative form of cooling, it’ll pass out like a penguin at the pyramids.

Close up photo of Intel CPU cooler blocked.

If you’re running a desktop, then take a peek at our guide, How do I clean dust from my PC?, to blast away any fluff, pet hair or spider webs (yes, really!) which can prevent cool air reaching the warmer parts of your PC.

Older desktops will often benefit from having the thermal paste replaced which sits between the CPU cooler and the processor. It starts life as a heat-conductive paste, but relentless heat-cycles slowly remove the moisture, leaving a desiccated residue. Once you’ve carefully removed the cooler, remove the old compound with cotton-buds, kitchen towel or similar and apply a little – I repeat – a little, fresh compound. Remember, you’re cooling a CPU, not icing a cake. Typically, it’s possible to spend a small fortune on product, but these products by Akasa, Arctic and Thermal Grizzly are sensibly priced.

How to clean a laptop safely

You may read other guides which recommend blowing compressed air into the fan vent, which is certainly a popular approach. However, as fluff and lint don’t magically vanish when blasted with air, this method is superb at pushing debris back into the fan to stop it turning. As we want to remove the blockage, rather than just moving it, we’ll need to get inside the laptop.

How do I do that? Carefully, would be my advice. The bottom cover on most modern laptops is easily removable, giving quick access to the cooling fan. Watch out for screws hidden under rubber feet and plastic tabs. Older laptops will have plenty of cables and wires holding things together, so work slowly and methodically. If you’re brave, and I apologise in advance for the dire quality of this product, there is a video of me stripping down a few different laptops. You may find it useful.

Photo of a blocked laptop fan.

Once inside, remove the fluff from the grill, fan and re-assemble. Again, if your laptop is getting on, you could also replace the CPU’s (and possibly GPU’s) thermal compounds.

How to test PC memory

Of course, your answer to why does my PC turn off by itself could be faulty hardware. A catastrophic RAM failure will prevent a machine from starting up, so bringing a working PC to a cold crash is certainly possible. Although RAM testing can be performed within Windows, there are better tools available. MemTest86 is a thorough (and free) solution which can be run directly from a USB stick. Normally I’d give you chapter and verse on how to do this, but PassMark has created a lovely step-by-step tutorial video of how to download, install and run the software. All you’ll require is a USB stick (8GB or above), Rufus (another free download) and a delightful gift to help persuade a friend or loved one that you need to borrow their laptop for 20 minutes.

Let MemTest run a few cycles and, if it even so much as sneezes, replace the RAM.

How to test a PC’s hard drive

Testing the hard drive of a PC is more complicated than testing the RAM. In ye-olden days, there was a clutch of bootable utilities which would thrash an ATA drive until it confessed to concealing bad sectors, but times change. If you can, start your PC, then download and run CrystalDiskInfo. The software gives a traffic-light style warning about the status of your drive and although it’s not a test, it’ll give you a good indication about the current state of your drive. If your SSD has a few years on the clock, then take a note of the drive’s wear percentage as trouble may not be far away. Alternatively, most premium SSD manufacturers such as Samsung, Kingston and Western Digital have their own diagnostic tools, which can test the drive for errors.

Screenshot of the Samsung Magician SSD management software

Any other suggestions?

Certainly have. Another reason that your Windows 11 computer will turn off by itself is due to power. Although laptop batteries should degrade gracefully, they can often fail earlier than the manufacturer intended, reducing the time difference between 80% full and empty to around three minutes. Use BatteryMon to have a look at the state of yours.

Desktop power supply units (PSUs) can also give out if faulty. Alternatively, if you’ve recently upgraded your gaming rig to gain frame rates over your rivals, then double check with the Coolermaster PSU checker to see if your trusty PSU still meets the requirements.

If you’ve got this far and your computer is still turning off by itself, then take a trip to your friendly neighbourhood PC repair shop. Tell them we sent you.

PC not starting? Stop Code errors?

About the author

Lee Grant

I can normally be found attacking things with screwdrivers in my small computer repair business or writing a column for PC Pro magazine.

I am also trying to solve a mystery involving David Bowie.

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