PC fans turn on for half second, then immediately shuts down.

Troubleshooting a Computer That Powers On Briefly Before Shutting Down

Building and maintaining a PC can sometimes lead to perplexing issues, especially when sudden hardware behavior occurs. One common problem is when the system’s fans spin momentarily and then the system shuts down immediately, leaving users scratching their heads. If you’re experiencing a similar issue, this guide aims to help you understand potential causes and systematic troubleshooting steps.

Problem Overview

This specific issue manifests as the computer’s fans starting up for approximately half a second upon pressing the power button, then instantly shutting down. Further attempts to power the system result in the same brief fan activity, with no response to power button presses during this state. Repeatedly disconnecting and reconnecting power yields the same pattern, indicating a persistent problem that requires dedicated diagnosis.

Initial Troubleshooting Steps

When facing this scenario, consider performing the following checks to isolate the root cause:

Verify Power Connections
Ensure all power cables from the PSU to the motherboard and components are securely seated.
Re-seat all connectors to rule out loose connections.
Test with Minimal Hardware Configuration
Remove all non-essential components, leaving only the CPU, one stick of RAM, and the GPU (if necessary).
Use integrated graphics if available, to eliminate potential GPU issues.
Use a Different Power Supply
Swap to a known-good power supply to determine if the current PSU is causing power issues.
Note: Certain PSUs like Corsair SF models operate with fanless or minimal fan activity at low loads, which can sometimes complicate troubleshooting.
Reseat or Replace Memory Modules
Reseat existing RAM modules carefully, ensuring they are in the correct slots.
Test each module individually to identify faulty RAM.
Swap out RAM with known-good modules if available.
Reset BIOS Settings
Short the CMOS reset pins on the motherboard or remove and reinsert the CMOS battery to reset BIOS configurations.
This can resolve issues stemming from BIOS misconfigurations.
Inspect the CPU and Motherboard
Remove the CPU to check for bent pins, debris, or damage that could cause POST failures.
Examine the motherboard for visible signs of damage or corrosion.
Wait and Observe
Allow the system to remain powered off for an extended period to