I replaced the thermal paste on my CPU, and now the computer powers on for about a second before shutting itself down. The fans spin briefly, so the system is receiving power. I removed the cooler again to check the paste, and the application looked fine. I didn't remove the CPU itself. What should I check to find the cause?
1 Answer
Start by checking that the CPU cooler is mounted evenly and firmly, with the fan plugged into the CPU_FAN header. Also make sure no power cables were loosened while working inside the case. Reseat the RAM and verify that the motherboard’s 24-pin and CPU power connectors are fully inserted. If the cooler was left loose, the system may shut down quickly because of CPU temperature protection.

I didn’t remove the CPU itself—only the cooler—so I’ll check the cooler mounting, RAM, and power connectors first.