I just finished building a new PC, but it will not stay powered on. When I press the power button, it starts for a fraction of a second, the case RGB and fans briefly light up, and then everything immediately turns off. The motherboard's main PSU connector appears to be plugged in correctly. I did not use any fan adapters and connected the fans to the motherboard headers. What should I check to find the cause?
4 Answers
Connecting fans directly to motherboard headers is normally fine, but make sure you have not overloaded a header or forced a connector onto the wrong type of header. Check the motherboard’s diagnostic LEDs or speaker codes while attempting to start it; those can indicate whether the issue is memory, CPU, graphics, or power.
Try starting it with only the essentials connected: motherboard, CPU and cooler, one RAM stick, graphics card if your processor needs one, and the PSU. Disconnect extra drives, USB devices, RGB controllers, and additional fans temporarily. Reseat the RAM and test one stick at a time in the slot recommended by the motherboard manual.
Since this is a first boot, start with the basic connections: confirm the 24-pin motherboard cable and the separate 8-pin CPU/EPS cable are both connected. Make sure the PSU switch is on, the front-panel power-switch connector is in the correct pins, and the CPU cooler is plugged into the CPU_FAN header. A missing CPU power cable can cause an immediate shutdown.
An instant power-off can also mean the board is shorting against the case or the power supply is detecting a fault. Check that the motherboard is mounted only on the correct standoffs, no loose screw is underneath it, and the CPU is installed properly. If possible, test the board outside the case on its box with the minimum components connected.
It is a brand-new build, so I have not successfully started it even once. I will recheck the CPU power connection and front-panel pins.