A PC that will not turn on is one of the most stressful situations a builder can face, but the cause is almost always something simple and fixable. This comprehensive troubleshooting guide walks you through the most common causes and their solutions in order of likelihood, helping you systematically identify and resolve the issue without unnecessary panic or expense.
Start with the absolute basics. Confirm the power cable is securely connected to both the power supply and the wall outlet, and verify the wall outlet is actually live by testing it with another device. Check that the power supply switch on the back of the unit is in the On position, marked with a line symbol rather than a circle. These obvious checks catch the problem more often than you might expect and save considerable troubleshooting time.
If the system shows no signs of life at all, meaning no fans spin, no LEDs illuminate, and no sounds occur, the issue is likely related to power delivery. Remove the 24-pin ATX cable from the motherboard and perform a PSU paperclip test to determine whether the power supply itself is functional. Bridge the green wire to any black ground wire on the 24-pin connector, plug the PSU into the wall, and turn it on. If the PSU fan spins, the unit is likely functional and the problem lies elsewhere. If nothing happens, the PSU may be faulty and requires replacement.
Front panel connectors are another frequent culprit. The tiny power switch, reset switch, and LED connectors that connect from your case to the motherboard are easy to misalign. Consult your motherboard manual for the exact pin layout and verify each connector is seated correctly. If in doubt, use a screwdriver to briefly short the two power switch pins on the motherboard header. If the system starts, the front panel power button connector was the issue.
RAM seating problems are extremely common, particularly for first-time builders. Remove all RAM sticks, reseat them one at a time with firm pressure until the retention clips snap into place, and try powering on with a single stick in the primary slot specified by your motherboard manual. If the system starts with one stick but not two, test each stick individually to identify a faulty module or try different slots to rule out a dead memory channel.
CPU installation issues can prevent boot. If you have recently installed or reseated the CPU, power off, remove the cooler, and carefully inspect the CPU socket for bent pins, which is more common on Intel LGA sockets, or verify the CPU is correctly oriented in an AMD AM5 socket using the alignment triangle. Even a single bent pin can prevent the system from powering on.
Motherboard standoffs are critical and sometimes overlooked. Ensure the motherboard is mounted on standoffs and that no extra standoffs are making contact with the back of the board where there are no mounting holes. An extra standoff creating a short circuit to the motherboard can prevent the system from starting or cause erratic behaviour.
If fans spin briefly and the system immediately shuts off, this often indicates a short circuit or a CPU power issue. Verify the 8-pin CPU power cable is connected, as many builders connect the GPU power cables but forget the separate CPU power connector located near the top of the motherboard. Also ensure you have not accidentally plugged a PCIe power cable into the CPU power connector, as they are physically similar but electrically incompatible.