Computer won't turn on

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.

The POST (power-on self-test) is a set of procedures that a computer runs through each time it is turned on. It ensures that all of the system's hardware is working properly before trying to load the operating system. If the computer does not pass POST, it will not boot.

If you're experiencing POST errors when you boot your computer, the following steps may help you fix the problem.

Tip

Make sure the computer turns on. If nothing happens (no lights, no sound, no fans, etc.), see: Why won't my computer turn on?

Caution

Some of the steps below recommend removing physical parts from inside the computer. While working inside the computer, it's highly recommended you be aware of ESD (electrostatic discharge) and its potential hazards.

Remove new hardware

If any new hardware was recently added to the computer, remove that hardware to make sure it is not causing your issue. If your computer works after removing the new hardware, it can mean a few things. Either the new hardware is not compatible with your computer, a system setting needs to be changed, or the new hardware is defective.

Identify beep code

If you are receiving a sequence of beeps, see the beep code page for a listing of different beep codes and their explanation. You can also check your motherboard or computer documentation for information on the beep codes. These beep codes are meant to help identify which computer component is failing or bad. If your beep code is not listed, continue troubleshooting.

Check all fans

Make sure all fans are running on the computer. If a fan has failed (especially the heat sink fan for the CPU), your computer could be overheating or detecting the fan failure, causing the computer not to boot.

Check all cables

Verify all the cables are securely connected to the computer and that there are no loose cables by firmly pressing in each cable.

All disk drives should have a data cable and power cable connected to them.

Your power supply should have at least one cable going to the motherboard. Many motherboards may also have additional cables connected to them to supply power to the fans.

Disconnect all expansion cards

If the above recommendations still have not resolved the irregular POST, disconnect the riser board (if applicable) and each of the expansion cards. If this fixes the problem or allows the computer to POST, connect one card at a time until you determine which card is causing the problem.

Disconnect all drives

If you cannot diagnose the problem by the beep code (or you do not hear a beep code), power off the computer. Then, disconnect any IDE, SATA, SCSI, or other data cables from the motherboard. When they are disconnected, try booting the computer again.

If this resolves your irregular POST or generates error messages, reconnect each device until you determine which device or cable is causing the issue. In some situations, it can also be a loose cable connection that causes the issue.

Remove the RAM

If you continue to experience the same problem with all the above hardware removed, remove the RAM from the motherboard and turn on the computer. If the computer has a different beep code or was not beeping but is now, turn off your computer and try the suggestions below. Make sure to turn off the computer before adding and removing the memory and then turning it back on to see if the suggestion resolves the issue.

Re-insert the memory into the same slot.

If you have more than one stick of memory, remove all but one stick of memory and try rotating through each stick.

Try one stick of memory in each slot.

If you can get the computer to boot with one or more of the sticks of memory installed, you are likely dealing with some bad memory. Try to identify which stick of memory is bad and replace it.

If you can get the memory to work in one slot but not another slot, the motherboard is likely defective. You can either work around the issue by running the memory in a different slot that does work or replaces the motherboard.

Power cycle the computer

In some situations, a computer may have power-related issues often caused by either the power supply or the motherboard. To help determine if this is the issue, try turning the computer on, off, and back on as fast as possible, making sure the computer power light goes on and off. In some situations, you may get the computer to boot.

Warning

Try this method only as a temporary workaround or as a last resort to get any valuable information from the computer.

Disconnect and reconnect the CPU

For users who're more comfortable working inside their computer, reseat the CPU by removing it and re-inserting it into the socket. You should also apply a fresh layer of thermal compound between the CPU and the heat sink.

Loose BIOS chip

If your motherboard has a BIOS chip, it can become loose over time due to heat expansion and cause the computer to give an irregular POST. Gently press down on the BIOS chip to make sure it has not become loose.

Bad motherboard, CPU, RAM, or power supply

If, after trying all of the above recommendations you still have an issue, you likely have a bad motherboard, power supply, CPU, or RAM stick. The next step would be either to replace these components or have the computer serviced. If you plan on doing the repairs yourself, we suggest you replace or swap in parts from another computer that is known to work. Replace the motherboard first, then the RAM, the CPU, and finally, the power supply.

Power cord not connected properly

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

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:

Crack in the circuit board.

Broken pins or prongs for an integrated circuit.

Melted integrated circuit due to overheating.

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.

Processor and heat sink

Video card

Sound card

Disc drive

RAM (memory)

Hard drive

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.