These my computer won’t turn on solutions are the same checks we use on our own bench when a PC arrives for repair. When a computer won’t turn on, it is easy to assume the worst, but most problems turn out to be simple: a loose cable, a switch in the wrong position, a stick of memory that has worked loose or a failing PC power supply. Work through the steps below in order and you will usually find the cause within minutes.
This guide covers desktop PCs first, then laptops. It explains how to tell what kind of failure you have, safe checks anyone can do, more advanced steps for confident users, and when it is time to call in a professional.
First, what does “won’t turn on” actually mean?
The fix depends on the symptom, so start by noticing exactly what happens when you press the power button.
| What you see | Most likely causes |
|---|---|
| Nothing at all: no lights, no fans | Power point, cable, power supply switch, front panel button, failed power supply |
| Fans and lights come on, but no picture | Monitor or cable, memory, graphics card, BIOS |
| Turns on for a second, then off | Short circuit, loose CPU power cable, failing power supply |
| Restarts over and over | Memory settings, overheating, power supply, BIOS |
| Starts but Windows will not load | Storage drive, boot order, corrupted Windows files |
Safety first
Before opening your PC, switch it off at the wall and unplug the power cable. Never open the PC power supply itself, as it can hold a dangerous charge even when unplugged. Touch a metal part of the case to discharge static before handling components, and work on a table rather than carpet.
Quick checks before you open the case
These checks solve a surprising number of cases and take only a couple of minutes.
1. Check the power point and power board
Plug a lamp or phone charger into the same outlet to confirm it works. If you use a power board, check its switch and try plugging the PC directly into the wall. Power boards with surge protection can fail after a storm.
2. Check the power cable and power supply switch
Make sure the power cable is pushed firmly into the back of the PC and the wall. On the back of the PC, find the switch on the power supply. The “I” position is on and the “O” position is off. Cleaners and pets knock these switches more often than you would think.
3. Drain residual power
Unplug the PC, then hold the power button for 30 seconds. This drains leftover charge, which can sometimes stop a computer from starting after a power cut. Plug it back in and try again.
4. Check the monitor
If the fans spin but the screen stays black, the computer may actually be on. Make sure the monitor is switched on, set to the right input and connected to the graphics card rather than the motherboard. Try a different cable or a different monitor if you have one.
5. Disconnect accessories
Unplug everything except the power cable, monitor, keyboard and mouse. A faulty USB device or hub can occasionally prevent a PC from starting.
Checks inside the case
If the quick checks did not help, it is time to look inside. Switch off at the wall, unplug the cable and remove the side panel.
6. Check the front panel power button connector
The power button on your case connects to a small header on the motherboard. If that connector has come loose, pressing the button does nothing. Check the motherboard manual for the location of the power switch pins and make sure the connector is firmly attached. On many boards you can briefly touch the two power switch pins with a screwdriver to start the PC, which confirms whether the case button is the problem.
7. Reseat the motherboard and CPU power cables
Find the large 24-pin cable on the right edge of the motherboard and the 8-pin CPU power cable near the top left. Unplug and firmly reconnect both. A partly seated CPU power cable is a classic reason a computer won’t turn on or turns off instantly.
8. Reseat the memory
Open the memory slot clips, remove each stick and press it back in firmly until the clips click. If it still will not start, try booting with a single stick in the slot recommended by your motherboard manual, then try each stick in turn. Faulty or loose memory is one of the most common causes of a black screen with fans spinning.
9. Reseat the graphics card and its power cables
Unplug the graphics card power cables, release the slot latch, remove the card and reinsert it firmly. Reconnect the power cables fully. On RTX 50 Series cards with a 16-pin connector, make sure there is no gap between the plug and the socket. If your processor has integrated graphics, you can remove the card and connect the monitor to the motherboard to see if the card is the problem.
10. Read the debug lights or beep codes
Many motherboards have small LEDs labelled CPU, DRAM, VGA and BOOT. The light that stays on points to the problem area. Older boards use beep codes instead. Look up the pattern in your motherboard manual. This one step can save a lot of guesswork.
11. Clear the CMOS
A bad BIOS setting, such as an unstable memory overclock, can stop a PC from starting. Clearing the CMOS resets the BIOS to default. Most boards have a clear CMOS jumper or button. Alternatively, with the PC unplugged, remove the round coin battery for a few minutes and refit it. You will need to re-enable your memory profile afterwards.
Is your PC power supply the problem?
A failing PC power supply is one of the most common hardware causes when a computer won’t turn on. Power supplies wear out over time, and cheap units fail far more often than quality ones.
Signs of a failing PC power supply
- No response at all after checking the outlet, cable and switch.
- The PC turns on briefly then shuts off.
- Random shutdowns or restarts under gaming load.
- A burning smell, crackling or buzzing from the back of the PC.
- Fans twitch but the system does not start.
How to test it
The safest test is to swap in a known good PC power supply of suitable wattage. Some power supplies include a self-test button, and inexpensive power supply testers are available. The paperclip test, which bridges two pins on the 24-pin connector to make the power supply start on its own, can confirm a unit is completely dead, but it does not prove the power supply is healthy under load. If you are not confident, leave this to a technician.
Choosing a replacement PC power supply
If your PC power supply has failed, replace it with a quality unit from a reputable brand with a good warranty. Choose a wattage that suits your graphics card with some headroom, check it has the connectors you need, including a native 16-pin cable for many RTX 50 Series cards, and look for an efficiency rating of 80 Plus Gold or better. A good PC power supply protects every other part of your computer.
The minimal boot test
If you are confident working inside a PC, a minimal boot test isolates the problem. Disconnect everything except the motherboard, processor, cooler, one stick of memory and the power supply. If the PC reaches the BIOS with integrated graphics, or the debug lights pass the DRAM stage, add components back one at a time until the problem returns. The last part added is the likely culprit.
When the PC turns on, then shuts off
A PC that starts and then shuts down after a few seconds or minutes usually has one of three problems: overheating, a power supply that cannot handle the load, or a short circuit. Check that the CPU cooler is mounted firmly and its fan is spinning, and that the cooler’s fan cable is plugged into the CPU_FAN header. Our guide on how to check CPU temperature shows what normal looks like. If shutdowns happen mainly while gaming, suspect the power supply.
When it turns on but Windows will not start
If you see the manufacturer logo or BIOS screen but Windows will not load, the hardware is probably fine. Enter the BIOS and check that your SSD is detected and set as the first boot device. If Windows shows a recovery screen, try Startup Repair. You can also boot from a Windows installation USB and choose Repair your computer. If the SSD is not detected at all, reseat it or try another slot.
Laptop won’t turn on
- Plug in the charger and check the charging light. Try a different power point.
- Leave it charging for 30 minutes if the battery may be completely flat.
- Perform a hard reset: unplug the charger and hold the power button for 30 seconds, then reconnect and try again.
- Connect an external monitor. If it works, the laptop screen or its cable may be faulty.
- Disconnect all USB devices and docks.
- If the laptop has a removable battery, remove it and try running on the charger alone.
Laptop repairs beyond these steps usually need a technician, especially for charging circuit or motherboard faults.
Warning signs before a computer won’t turn on
Hardware often gives hints before it fails completely. Spotting them early can save your files and avoid the day your computer won’t turn on at all.
- Random restarts or shutdowns, especially under load, often point to an ageing PC power supply or overheating.
- Clicking or grinding noises can come from a failing fan or an old hard drive.
- Slow or failed starts that need several attempts suggest power delivery or memory problems.
- Blue screen errors that mention memory or hardware are worth investigating straight away.
- A hot, dusty case is a warning that cooling is struggling.
If you notice any of these, back up your important files immediately, then investigate. It is much easier to fix a computer that still works than one that won’t turn on.
Preventing future start-up problems
- Use a quality surge-protected power board, especially in storm-prone areas.
- Shut down properly rather than switching off at the wall.
- Keep the inside of the PC clean to avoid overheating.
- Choose a reputable power supply rather than the cheapest available.
- Do not overtighten or force connectors when upgrading parts.
Computer won’t turn on after an upgrade
If your computer won’t turn on right after you installed something new, the new part or the way it was fitted is the prime suspect. Recheck every connector you touched. A graphics card upgrade often needs extra power cables, and a new card may need more power than the old PC power supply can deliver. Memory upgrades can fail if the sticks are in the wrong slots or if a new kit is not compatible with the old one. If you updated the BIOS and the computer won’t turn on afterwards, try clearing the CMOS. When in doubt, refit the old part to confirm whether the upgrade is the cause.
Computer won’t turn on after cleaning or moving
Moving a PC, or giving it a thorough clean, can shake connectors loose. Heavy graphics cards can work partly out of their slot, and memory sticks can lift slightly. Open the case and press each component and cable firmly back into place. If you used compressed air, make sure no fan was spun so hard it damaged the bearings, and that every fan cable is still connected.
High-end gaming PC won’t turn on
Powerful gaming systems draw a lot of current, which puts more stress on the PC power supply and its cables. If a high-end gaming computer won’t turn on, pay special attention to the graphics card power connection, especially the 16-pin connector used on many RTX 50 Series cards. It must be fully seated with no gap. Also confirm the PC power supply has enough wattage for the card. Our RTX 5090 guide explains the power needs of the most demanding cards.
How we diagnose a computer that won’t turn on
When a PC comes in to our workshop, we follow a set process. We start with the simplest my computer won’t turn on solutions: power, cables and switches. Then we read any debug lights, test the PC power supply on a tester and under load, and try a minimal boot with known good parts. This isolates the faulty component quickly, so we only replace what is actually broken. Most of the time the fix is a single part rather than a whole new computer.
Power supply myths
Two myths cause a lot of problems. The first is that wattage is all that matters. A cheap unit with a high wattage label can deliver less clean power than a quality unit rated lower. The second is that a PC power supply lasts forever. Components inside age with heat and use, so a ten-year-old unit in a new build is a risk. Choose a quality PC power supply and it will protect everything else.
Quick recap
To summarise these my computer won’t turn on solutions: check the outlet, cable and power supply switch, drain residual power, confirm the monitor connection, reseat the power cables, memory and graphics card, read the debug lights, clear the CMOS and test the power supply. If your computer won’t turn on after all of that, it is time for professional help.
When to get professional help
If you have worked through every step and the PC still will not start, or if you notice a burning smell, visible damage or swollen components, stop and get professional help. Continuing to power on a faulty system can damage other parts.
If your PC is under warranty, contact the seller before opening it, as some warranties have conditions about opening the case. Australian buyers are also protected by consumer guarantees, explained by the ACCC. Every PC we sell has a 12-month warranty with support from the team that built it, so if you bought from us, send us a message describing the symptoms.
Is it time for a new computer?
If your computer is more than six or seven years old and needs a new motherboard or processor, replacement is often better value than repair. Many older PCs also cannot run Windows 11 now that Windows 10 support has ended. Our desktop computers range includes reliable systems for home, study and business, such as the home and study desktop PC and the silent business computer.
Computer won’t turn on FAQ
Why won’t my computer turn on but the lights are on?
If lights and fans come on but there is no picture, check the monitor connection, then reseat the memory and graphics card. Debug LEDs on the motherboard often point to the cause.
Can a bad PC power supply damage other parts?
A poor quality power supply can damage components when it fails. Quality units include protections that shut down safely instead.
How long does a PC power supply last?
Quality units commonly last seven to ten years or more. Cheap units can fail much sooner.
My computer won’t turn on after a storm. What should I do?
Check the power board first, as surge protectors can trip or fail. If the PC still will not start, the power supply may have been damaged and should be tested.
Is it safe to fix a computer myself?
The checks in this guide are safe if you unplug the PC first and never open the power supply. If you are unsure at any point, ask a professional.
