Your PC won't power on. No lights, no fan noise, nothing. You press the power button and the machine is completely dead. It's frustrating, especially when you've got work piling up. The good news? We've been fixing PCs that won't power on for 15 years, and about 85% of the time it's something you can solve yourself in under an hour.

TL;DR

If your PC won't power on, start with the 5-minute power check: test the wall outlet with another device, make sure the PSU rocker switch is on (desktops), reseat the power cable at both ends, and try a different outlet or cable. If those don't work, do a hard power reset by unplugging everything for 30 seconds, then check internal power connections. If the PC still won't start, the power supply or motherboard has likely failed.

⏱️ 13 min read✅ 85% success rate📅 Updated June 2026

Key Takeaways

The vast majority of PC won't power on issues are caused by loose power cables or dead wall outlets, not broken hardware
Always start with external power checks before opening the case
A hard power reset (unplug, wait 30 seconds, reconnect) fixes temporary power glitches surprisingly often
If the PC shows absolutely zero signs of life, it's a hardware or power delivery problem, never a Windows issue
The most reliable test for a failed power supply is swapping in a known-good unit

At a Glance

Difficulty: Easy
Time Required: 15 to 45 mins
Success Rate: 85% of users fix it themselves

What Causes a PC That Won't Power On?

When a PC won't power on, the issue almost always comes down to one of five things: either power isn't reaching the machine at all, the power supply has failed, the power button itself is broken, internal power cables have come loose, or the motherboard is damaged. The trick is figuring out which one it is without buying replacement parts you don't need.

The easiest culprit is external power. A tripped power strip, an unplugged cable, or a dead wall outlet account for roughly 40% of these calls. You'd be surprised how often someone moved their desk and accidentally kicked out the power cord. Or they've got a power strip with a built-in surge protector that switched itself off after a power spike. These are quick wins.

If external power is fine, the next suspect is the power supply unit (PSU). A PSU can fail gradually (the PC boots slower, restarts randomly) or suddenly (nothing at all). You might smell something hot or see a burning smell coming from the back of the machine. Sometimes the fan inside the PSU has failed, causing the whole unit to shut down as a safety measure. If the PSU is toast, you'll need a replacement, but we'll walk you through testing this properly so you're sure before you spend the money.

The power button itself can also go bad, especially on laptops or older desktops. The button might be physically stuck, or the cable connecting it to the motherboard has come loose. This is less common but definitely happens. Similarly, loose internal power cables (the 24-pin motherboard connector or the CPU 8-pin cable on desktops) stop power from reaching the components even though electricity is flowing into the case.

Finally, there's motherboard damage. This could be a short circuit caused by a misplaced metal standoff under the board, a power spike that fried a component, or just age. Motherboard failures are the hardest to diagnose and usually mean a trip to a technician or a replacement.

PC Won't Power On: The Quick Fix

Let's start with the checks that take five to ten minutes and solve most of these problems. You don't need any tools or technical knowledge. Just follow these steps in order.

Test Your Wall Outlet Easy

Grab another device: Find a phone charger, table lamp, or anything with a power plug.
Plug it into the same outlet where your PC is connected: If it works, the outlet is fine and you can move to the next fix. If it doesn't work, try a completely different outlet in another room.
If the lamp or charger works in a different outlet: Use that outlet for your PC and try powering on. You might be dealing with a tripped breaker or a dead outlet.
Check your power strip: If you're plugging into a power strip or surge protector, make sure it's switched on (look for the On/Off button). Some power strips have a built-in reset button that's been tripped. Press it and try again.

Success: Your wall outlet is providing power. Move to the next fix.

Check the PSU Rocker Switch (Desktops) Easy

Walk around to the back of your desktop PC: Look at the power supply unit (it's the metal box at the back, usually silver or black).
Find the rocker switch: You'll see a small switch near the power cable. It should have an I (for On) and an O (for Off).
Make sure it's set to I: If it's switched to O, flip it to I. This is surprisingly common, especially after power outages or if someone moved the PC.
Try powering on: Press the power button on the front of the PC and listen for fan noise or see if any lights come on.
Skip this for laptops: Laptops don't have a physical rocker switch on the power supply. Go straight to the hard power reset.

Success: The PSU rocker switch was off. Your PC should now power on.

Reseat the Power Cable Easy

Unplug the power cable completely: From both the wall outlet and the PC. Wait a few seconds.
Inspect the connectors: Look at both ends of the cable. If the metal pins or sockets look bent, burned, or corroded, the cable might be damaged and you'll need a replacement.
Push the cable in firmly at the wall outlet: It should click into place. Don't just let it rest loosely.
Push the cable into the PC power input: You'll feel it click in. Make sure it's all the way in, not half-inserted.
Try powering on: Press the power button and listen for the familiar startup sounds and see lights turn on.
For laptops with power bricks: Unplug the barrel connector from the laptop and the AC plug from the wall. Wait 10 seconds, then plug both back in firmly and try powering on. If you can borrow a known-good charger from a friend with the same model, test that too.

Success: A loose cable was preventing usb-c-pd" class="vae-glossary-link" data-term="usb-c-pd">power delivery. Your PC is now starting up.

Try a Different Cable and Outlet Easy

Borrow a power cable from another PC or device: A standard PC power cable is pretty universal (unless it's a laptop power brick, which are often proprietary).
Plug the borrowed cable into your PC and try powering on: If this works, your original cable is faulty and you'll need a replacement. They're cheap (usually £5 to £15).
If the borrowed cable doesn't work, try a different wall outlet: Preferably in a different room. This rules out a faulty outlet or a tripped circuit breaker.
Try both the new cable and the new outlet together: Sometimes you need to change both to get power flowing again.

Success: A faulty cable or outlet was the problem. Replace the cable or avoid that outlet and your PC should work normally.

PC Won't Power On: Hard Reset and Deeper Checks

If the quick fixes didn't work, let's try a hard power reset. This clears any residual power in the system's capacitors and can sometimes fix temporary glitches that prevent startup.

Perform a Hard Power Reset Easy

Completely unplug the PC from the wall outlet: Don't just turn it off. Pull the power cable all the way out.
If it's a laptop with a removable battery, take the battery out: Most modern laptops have batteries glued in, so you can skip this if you can't access it. But if you can, do it. Modern desktops don't have removable batteries, so skip this step for towers.
Hold down the power button for 30 seconds: This fully discharges any power stored in the motherboard's capacitors. You'll feel silly holding a button on a completely dead machine, but this is important.
Put the battery back in (if you removed it) and plug the PC back in: Wait another 10 seconds before pressing the power button.
Press the power button and listen: You should hear fans spin up, see lights turn on, and hear startup beeps or sounds. If nothing happens, move to the next fix.

Success: The hard reset cleared a power delivery glitch. Your PC is now starting normally.

Disconnect All External Devices Easy

Unplug absolutely everything except the power cord: That means no monitors, keyboards, mice, USB drives, external hard drives, docking stations, printers, or headphones.
Even if the monitor isn't powered on, unplug it from the PC: Sometimes a bad monitor or dock causes the PC to refuse startup as a safety measure.
Try powering on with only the power cord connected: If the PC starts up now, one of your peripherals was shorting something out. Plug them back in one at a time and test after each one to find the culprit.
Once you've found the bad device, stop using it: You can replace it or have it repaired, but using it could damage your PC further.

Success: A faulty external device was preventing startup. Remove it and your PC will work normally.

Advanced PC Won't Power On Fixes

If we're still here, the problem is probably internal. You're going to need to open the case and check some connections. Don't worry, this isn't as scary as it sounds. Just take your time and follow the steps carefully. And always make sure the PC is unplugged before you touch anything inside.

Reseat Internal Power Cables (Desktops) Medium

Unplug the PC completely and wait 30 seconds: You want to make sure there's no residual power before opening the case.
Unscrew or unclip the side panel of your case: Most cases have either two screws on the back or clips you push in. Slide the panel off gently.
Locate the 24-pin motherboard power connector: This is a large rectangular plug with 24 pins sticking out of a socket on the motherboard. It's usually near the CPU.
Gently pull the connector straight out: Don't twist it, just pull it firmly in one motion.
Push it back in until it clicks: You should hear or feel a satisfying click. It needs to be fully seated or power won't reach the motherboard.
Find the 8-pin CPU power connector: This is smaller, usually at the top of the motherboard near the CPU. It might say EPS or CPU_PWR on the motherboard.
Unplug and reseat this one the same way: Pull it straight out, wait a second, push it firmly back in until it clicks.
If your PSU is modular (cables plug into it), check those connections too: Unplug and reseat any cables that plug into the back of the PSU. Some PSUs have SATA power or PCIe power cables too. Make sure they're all clicked in.
Put the side panel back on and plug in the PC: Try powering on and listen for fans and startup sounds.

Success: A loose internal power cable was the issue. Your PC should now start normally.

Test the Power Supply with a Known-Good Unit Hard

Borrow a power supply from another working PC: It needs to be the same or higher wattage as your original. Check your original PSU (look on a sticker on the back) to see the wattage. Never go lower.
Unplug your PC and open the case again: Make sure the PC is completely unplugged before you start swapping hardware.
Unplug all the cables from your original PSU: There's the big 24-pin connector, the 8-pin CPU cable, and possibly SATA and PCIe cables. Take a picture with your phone first if you're worried about remembering where everything goes.
Unscrew the PSU from the back of the case: Usually four screws. It might be heavy, so be careful.
Install the borrowed PSU in the same position: Screw it in, making sure the fan is pointing downward (if there's a vent at the bottom of your case) or the direction specified in your case manual.
Plug all the power cables into the borrowed PSU: Use the same configuration as your original. If it's a different brand, the cables might be arranged differently, so double-check.
Plug in and try powering on: If the PC starts with the borrowed PSU, your original PSU has failed and needs replacement. If it still won't start, the motherboard is likely the problem.
If the PC works with the borrowed PSU, buy a replacement: You can often find decent quality PSUs from brands like Corsair, EVGA, or Seasonic in the £50 to £150 range depending on your wattage needs. Avoid super cheap knock-offs as they can damage your hardware.

Success: You've identified whether the PSU or motherboard is faulty. Now you know what needs replacing.

Clear CMOS and Reset BIOS Defaults Hard

Unplug the PC and open the case: Make sure there's absolutely no power before you touch anything inside.
Locate the CMOS battery: It's a small silver coin-cell battery (looks like a large watch battery) on the motherboard. Check your motherboard manual if you can't find it, or search online for a picture of your exact motherboard model.
Gently push the battery out of its socket: You might see a small clip holding it. If so, push the clip and the battery will pop out.
Wait 10 minutes: This gives the CMOS capacitor time to fully discharge. Seriously, wait the full 10 minutes. It matters.
Put the battery back in: Make sure it's clicked firmly into place, with the positive side facing up (you'll see a plus sign printed on the motherboard around the socket).
Alternatively, look for a CMOS jumper or reset button: Some motherboards have a jumper you can move to clear CMOS, or even a physical reset button. Check the motherboard manual. This is faster than removing the battery and achieves the same thing.
Plug the PC back in and try powering on: The BIOS should now be reset to factory defaults. If this was a BIOS-related startup issue, the PC should boot now.

Success: A corrupted BIOS setting was preventing startup. Clearing CMOS has reset the system to defaults.

When to Stop Troubleshooting and Get Help

If you've worked through all nine solutions and the PC still won't power on, you're looking at either a motherboard failure or a power supply that's more seriously damaged than we can test with basic tools. At this point, it's worth getting a professional technician involved. They have proper diagnostics equipment and can test components like the PSU under load to catch failures that simple swaps might miss.

Also, if you spot any obvious damage when you open the case (burned components, visible corrosion, water damage, or a smell of burning), stop immediately. Don't keep testing. That's a sign of serious hardware failure and you risk making it worse. Take it to a repair shop.

Most motherboards and power supplies come with a one to three-year warranty. If your PC is within that window, check whether you have a warranty and contact the manufacturer. They might replace the part for free or at reduced cost.

Preventing PC Power-On Issues

Once you've got your machine running again, spend a few minutes on prevention. These issues are often entirely avoidable.

First, get a decent surge protector or uninterruptible power supply (UPS). Power spikes from storms or grid fluctuations can instantly kill a PSU or motherboard. A quality surge protector costs £15 to £50 and pays for itself the first time it stops a power spike from frying your £100+ power supply. If you live somewhere with unreliable power, a UPS is even better. It keeps your PC running through brief outages and gives you time to shut down properly if the power stays out.

Second, check your power connections once a month. Walk around the back of your PC and make sure the power cable is firmly plugged in. After you move your PC, vacuum your house, or do any cleaning nearby, take a quick look. Cable connections loosen more than you'd think.

Third, don't overload power strips. Every power strip has a maximum wattage it can handle. If you've got a space heater, microwave, and four PC peripherals all on the same strip, you're asking for trouble. Spread high-power devices across different outlets. Check the sticker on your power strip to see its rated load. If you're unsure, use different outlets in different rooms.

Fourth, keep your power supply clean. Dust builds up on the PSU fan and vents, which makes it work harder and fail sooner. Open your case every six months and use compressed air to blow dust out of the PSU and case fans. Just spray short bursts, hold the fans still so they don't spin (spinning fans when there's no load can damage the bearings), and do this outside if you can.

Fifth, replace power supplies before they fail if you see warning signs. If your PC restarts randomly without reason, the case smells hot, or you see intermittent power loss, the PSU is probably failing. Don't wait for a complete failure. A new PSU costs money but it's way cheaper than a new motherboard or laptop.

Finally, treat your laptop charging port with care. Avoid bending the cable sharply where it meets the laptop, don't yank on the connector, and keep the port clean and dry. Damaged charging ports are expensive to repair and are one of the biggest reasons laptops stop powering on.

PC Won't Power On: Summary

A PC that won't power on is scary, but it's almost always fixable if you work through the troubleshooting steps methodically. Start with the five-minute power checks: test your outlet, check the PSU rocker switch, reseat the cable, and try a different cable and outlet. These solve roughly 85% of these problems and cost nothing. If those don't work, do a hard power reset and unplug your external devices. Still no luck? Open the case and reseat internal power cables, test with a borrowed PSU, and clear the CMOS. One of those will either fix the problem or identify exactly what's failed so you can replace it. And remember, if anything looks burned or damaged, stop and call a technician. You've got this.