Why does this PC randomly shut down and refuse to boot for hours?
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VelvetCactus42
A friend's desktop PC powers off unexpectedly at seemingly random times. After shutting down, it sometimes won't start again for several hours. It doesn't appear to be a simple outlet problem: the computer behaves the same when connected directly to the wall, and the power supply was replaced last year. What should we check to diagnose the cause?
Answers
A surge protector doesn’t completely rule out power-quality problems, but the first checks should be inside the PC. Look for heavy dust, disconnected or loose cables, swollen capacitors, and fans that aren’t running. If it still happens after cleaning and temperature testing, stop using it until the PSU and motherboard can be tested safely.
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Overheating is one of the most likely explanations. A failing or clogged fan, blocked vents, or a heatsink packed with dust can make the system shut itself off for protection. Clean the inside with compressed air, check that every fan spins, and monitor CPU and GPU temperatures. Don’t keep using it under load if temperatures are unusually high.
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More system details are needed before narrowing it down: the CPU, graphics card, motherboard, power supply model, operating system, and whether it shuts off during gaming or even while idle. Check Event Viewer after the next restart for critical shutdown events, although sudden power loss often won’t leave a useful software error.
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The computer may be waiting until a failing component cools down, but several hours is longer than normal. A bad power supply, loose power cable, defective case power switch, or failing motherboard component could also cause this. Since the replacement PSU is already a year old, testing with a known-good unit would still be worthwhile.
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