Why won't my computer turn on?

Updated: 02/01/2021 by Computer Hope
Computer monitor with a black screen.

If you have a desktop computer that does not turn on after pressing the power button, use the following information and troubleshooting steps to help fix the problem.

Note

This page relates primarily to desktop computers. If you have a laptop that won't turn on, see: Why does my laptop not turn on?

I'm not sure if my computer is turning on

If you're uncertain if the computer is turning on, check if the case fan (generally on the back of the computer) is spinning. If a fan is spinning, the computer is getting power, and this page may not apply to your issue.

Note

If the computer turns on but doesn't pass a POST, sounds a beep code, or isn't showing any picture on the display, see: POST troubleshooting steps.

Power cord not connected properly

Computer power cord

It may seem obvious, but verify the power cord is connected to the back of the computer and plugged into a power outlet. If it appears to be connected correctly, disconnect and reconnect both ends of the power cord to ensure the cable is not loose.

Power strip or outlet

If you have a power strip (surge protector) or UPS (uninterruptible power supply), disconnect the computer power cord from it and connect the cord directly to the wall outlet.

If connecting the computer directly to the wall outlet still does not work, verify the outlet works by connecting another electrical device.

Bad power cable

Verify the cable supplying power to your computer is not bad or damaged, by swapping it out for another one.

If you don't have another power cable to test with, see if a friend or a family member has one you can borrow. You can also purchase a new power cable online.

Tip

Some computer monitors may use the same type of power cable as your computer. If your monitor power cable is removable and has the same type of connector, try using it to power the computer.

Power supply switch

Computer power supply

Some computer power supplies, like that shown in the pictures, have a power switch on the back. Check the back of the computer and make sure there are no additional buttons that are turned off.

Tip

A power supply switch often has a "0" and "1" which is binary for "off" (0) and "on" (1).

Incorrect power supply

If you built the computer and cannot get it to turn on, the power supply may be defective or is insufficient for your hardware's needs. Verify the power supply meets the requirements of your motherboard, processor, and video card.

Third-party hardware

If any computer hardware was recently added, we recommend you temporarily disconnect or remove it to ensure that it's not causing your issue.

Note

If, after you've added new hardware, the computer turns on but is not beeping and the monitor isn't displaying anything, see: POST troubleshooting steps.

Bad power supply, button, power board, or inverter

If, after following the steps in the sections above, your computer still receives no power, the power supply may have failed. If you don't want to replace it yourself, we suggest taking the computer to a repair center.

If you have a desktop computer and plan on trying to repair it yourself, open the computer and verify the power connections. You can do so by disconnecting the main power cable and reconnecting it to make sure it has not become loose. Also, verify the power button cable is correctly connected to the motherboard.

You can also test the power supply using a multimeter to check if it outputs the correct voltage. If the voltage output is low, the power supply is likely bad and needs to be replaced.

Loosely connected hardware

Each time your computer tries to turn on, it runs a POST. If any of the computer hardware components fail this test, the computer does not continue to boot.

Note

When working inside your computer's case, take appropriate precautions to prevent ESD that may damage sensitive electronics.

Unplug all cables from the back of the computer. Open the computer and reseat all expansion cards and memory. After these cards are reseated, make sure all cables are firmly connected by disconnecting and reconnecting them.

After everything is disconnected and reconnected, connect only the power cable to the back of the computer, then try turning it on. If the computer turns on, you can turn it back off and reconnect all the cables.

Bad motherboard

If the power supply connections look ok, but the computer still doesn't turn on, the motherboard may be bad. First, open the computer case and do a visual check of the motherboard. Look for any bulged or blown capacitors.

If you recently did soldering work on your motherboard, some of the solder may have connected two or more contact points that it shouldn't have. Those improper connections can cause the computer to not power up or boot.

Other possible causes for motherboard failure include the following:

While you can try replacing a bulged or blown capacitor, it's very likely that the motherboard defects above require that it be replaced.

Other bad hardware components

If the power supply and motherboard are in good shape and confirmed to not be the problem, another component may be bad. Try replacing the following hardware components in the order listed.

Note

A defective disc drive, RAM, or hard drive often doesn't cause a computer to not power up or boot. However, it's still possible they could cause a powering up problem if they are shorting out the motherboard in some way.