Computer powers on and then immediately turns off
If your computer turns off immediately or even within a few seconds after it is turned on, it could be due to several possible issues.
Note: See our no power or computer does not turn on document if the computer is not coming on at all and if the computer has been on for several minutes before it turns off see our computer turns off without warning document.
Caution: Some of the steps below require you open your computer. While in the computer, be cautious of ESD.
As a safety precaution, the computer is designed to turn off if a component in your computer has exceeded a set temperature. Open the computer, turn on the computer, and while the computer is on make sure all fans in the computer and power supply spin. If a fan or heat sink is bad, the computer could be overheating, or the computer may detect that the fan is not working and turn off the computer.
If this is a new computer or the motherboard has been recently replaced, make sure that the thermal compound is properly applied to the processor. If the heat is not being properly transferred from the CPU to the heat sink, it can overheat almost immediately.
If the problem persists, make sure all cables inside the computer case are firmly attached to the motherboard and each component. You'll want to check the IDE cables and SATA cables, which are typically connected to the hard drive, CD or DVD drive, and floppy drive (if present). Check both ends of each cable and make sure they are firmly attached to the component and the motherboard. Turn on the computer and test to see if this resolves the issue.
Tip: Sometimes the best way to verify a cable is not loose is to disconnect and then re-connect the cable on both ends.
Verify the memory modules are properly seated in the memory slots. To check and fix this, open the computer, remove the memory modules from the memory slots and re-insert them, making sure the clamps on both side of each memory chip snap into place and the memory chips are firmly seated in the memory slots. Plug in the power cord and turn the computer on to see if the issue is resolved.
Power supply issue
If the problem persists further, the next thing to check is the power supply. A faulty power supply can result in not enough, if any, power getting to the motherboard, which would cause the computer to shut off immediately or not turn on at all. In the event of a bad power supply, the only remedy is to replace it with a new one. Fixing a power supply is not economical, if possible at all.
Tip: If you suspect the power supply or none of the above options help resolve the issue, the first piece of hardware we suggest replacing is the computer power supply.
The last thing to check would be the motherboard; however, this can be rather difficult since the issue could be just about anywhere in the circuitry. A faulty circuit or malfunctioning component (e.g. capacitor) can cause the computer to shut off immediately or not turn on at all. If none of the above recommendations help resolve the issue we suggest replacing the motherboard or sending the computer to a repair shop.