Start with the power source before assuming the computer is broken

A computer that won't turn on is usually not dead—it is usually not receiving power. Before you worry about internal damage, check whether electricity is actually reaching the machine. This means looking at three things in order: the wall outlet, the power cable, and the power button itself.

Plug a lamp or phone charger into the same outlet your computer uses. If that device works, the outlet has power. If it does not, try a different outlet in another room. If nothing works in that outlet, you may have a tripped circuit breaker—go to your electrical panel and look for any switches in the "off" position, then flip them back to "on". If the outlet works but your computer still will not start, move to the next step.

Look at the power cable where it connects to the back of the computer. Make sure it is pushed in firmly—cables can work loose from vibration or being bumped. Follow the cable all the way to the wall outlet and check that connection too. If the cable looks damaged (frayed, bent sharply, or discolored), do not use it; get a replacement cable before trying again.

Key Takeaways

  • Test the wall outlet with another device like a lamp to confirm power is reaching it before assuming your computer is broken.
  • Push the power cable firmly into both the computer and the wall outlet, and inspect it for damage along its entire length.
  • Press and hold the power button for ten seconds, then release—some computers need a longer press than others.
  • If you see lights or hear fans but no display appears, the computer may be on but the monitor is off or disconnected.
  • A computer that was working until a power outage or storm may have a tripped surge protector or damaged power supply, which usually requires professional repair.

Check whether the power button is actually working

The power button can fail without the rest of the computer being damaged. Press it once and wait three seconds. If nothing happens, try pressing and holding it for ten seconds, then release. Some computers, especially older ones, need a longer press to wake up.

While you are holding the button, listen for sounds inside the case. You should hear the fan spin up and possibly a beep. If you hear those sounds but the screen stays dark, the computer is turning on—the problem is with the display, not the power. If you hear nothing at all, the power button itself may be stuck or broken, or power is still not reaching the motherboard.

Distinguish between "no power" and "power but no display"

These are two different problems that need different fixes. A computer with no power shows no lights, makes no sound, and does not respond to the power button. A computer with power but no display will have lights on the case or keyboard, the fan will spin, and you may hear beeping—but the monitor shows nothing.

If you have power but no display, check that the monitor itself is on. Look for a light on the monitor's front panel. If the monitor is off, press its power button. If the monitor is on but still dark, make sure the cable connecting it to the computer is pushed in firmly at both ends. Try unplugging the monitor cable, waiting ten seconds, and plugging it back in.

If the monitor cable is find and the monitor is on, try connecting the monitor to a different computer if you have one available. This tells you whether the monitor is broken or whether the video output on your computer is broken. If the monitor works on another computer, your computer's graphics hardware may need professional repair.

What to do if the computer was working until a power outage or storm

A sudden loss of power or a lightning strike can damage the power supply—the component inside the computer that converts wall electricity into the right voltage for internal parts. After an outage or storm, a computer that will not turn on at all may have a damaged power supply rather than a dead battery or loose cable.

Do not keep pressing the power button repeatedly. Unplug the computer from the wall for thirty seconds, then plug it back in and try once. If it still will not start, the power supply likely needs replacement. This is not a repair you should attempt yourself—a professional can test the power supply and replace it safely.

If you use a surge protector (the power strip with the outlet), check whether it has a reset button. Some surge protectors have a built-in breaker that trips during a power surge. Look for a small button labeled "reset" on the front of the surge protector, press it, and try turning on the computer again.

Check the battery if you have a laptop

Laptops have a rechargeable battery that can fail independently of the power supply. If your laptop will not turn on, plug the charger in and leave it connected for at least thirty minutes. Some laptops have a completely dead battery and need time to charge before they will respond to the power button.

While the charger is plugged in, look for a light on the charger itself or on the laptop. Many chargers have a small LED that glows when they are working. If the charger light is off, the charger may be broken. Try borrowing a charger from someone with the same laptop model and try again.

If the laptop still will not turn on after charging for thirty minutes, hold the power button for fifteen seconds. Some laptops have a safety feature that requires a longer press after the battery has been completely drained. If nothing happens after that, the battery or motherboard may be damaged and will need professional diagnosis.

When to stop troubleshooting and call a professional

If you have confirmed that power is reaching the computer, the power button responds, and the monitor is working but the computer still will not start, the problem is inside the computer itself. This could be a failed motherboard, a bad power supply, or damaged memory—none of which are safe to repair without training.

Take the computer to a repair shop or contact the manufacturer's support line. Have ready the model number (usually on a sticker on the case) and a description of exactly what you see and hear when you press the power button. A technician can test the internal components and tell you whether repair is worth the cost.

If the computer is still under warranty, contact the manufacturer before taking it anywhere else. Many manufacturers will repair or replace a computer that will not turn on at no cost during the warranty period.

Frequently Asked Questions

My computer has lights on but the screen is completely black. Is it on or off?

It is on. Lights on the case or keyboard mean power is reaching the motherboard. The black screen means the monitor is off, disconnected, or the graphics card is not working. Check that the monitor power button is pressed and the cable is firmly connected to both the monitor and the computer.

Should I keep pressing the power button if nothing happens?

No. Press it once and wait five seconds. If nothing happens, press and hold for ten seconds, then stop. Pressing repeatedly can damage the button or confuse the computer's startup sequence. Wait a full minute before trying again.

My computer was working fine until the power went out. Why won't it turn back on?

A power outage can damage the power supply inside the computer or trip a surge protector. Unplug the computer for thirty seconds, plug it back in, and try once. If it still will not start, the power supply likely failed and needs replacement by a professional.

Is it safe to open the computer case and look inside?

Not if you are trying to fix a power problem. Opening the case can expose you to electrical shock, and moving components around can cause more damage. If the power cable is find and the outlet works, the problem is inside and needs professional diagnosis.

What if my computer turns on for a second and then shuts off again?

This usually means the power supply is failing or a component is overheating. Do not keep trying to turn it on. Unplug it and take it to a repair shop. Repeated attempts can cause more damage.