PC suddenly shuts down, then restarts normally

Hi everyone,
About two months ago, my PC was running perfectly fine. Then, out of nowhere, it started shutting down abruptly—almost like someone pulled the plug—only to reboot itself immediately. It doesn't happen constantly, but usually in the evening, it might cycle like that two or three times... The build is nearly a year old and everything is relatively new. I've run full antivirus scans and cleared out a few minor threats, but nothing seems to help. I doubt it's an overheating issue since my cooling is solid; I'm running seven fans total. If anyone has any ideas, I would be very grateful.

Specs if needed:
CPU: Intel Pentium G3220 3.0
GPU: AMD Radeon R7 200 Series Saphire OC edition 2Gb
RAM: Kingston DDR3 1x4Gb 800MHz
Motherboard: Gigabyte H81M-S2PV
HDD: Seagate Barracud 1000
PSU: Corsair VS550

There could be a few different culprits here—for instance, dust buildup can really mess with your temps. It doesn't matter if you've got 65 fans running in your case; the dust is going to find its way in eventually. You might want to download a little utility called HWMonitor and take a look at what those temperatures are actually doing.

Also, there's always the possibility that the power supply is acting up...

Yeah, honestly, plenty of people slap a bunch of fans in their rigs without actually setting them up right, so the air just sits there stagnant. Of course it's going to overheat. The easiest way to check if heat is the culprit is to pop the side panel off, blow out any visible dust—be careful and make sure the PC is powered down first—and just leave it open to get some decent airflow. If it keeps crashing after that, then we know it's not the temps, and we can start looking elsewhere...

I'm putting my money on the power supply 🙂

Honestly, I don't think you're looking at a temperature issue here, man. It feels more like those fans are just sucking up way too much juice, and once you cross whatever wattage limit that power supply can actually handle, the whole thing just trips and restarts... it's a classic power draw spike. Just try unplugging like three of the fans and see if that stabilizes things...

Give me a break, don't say stuff like that unless you want people to think you actually know what you're talking about. What do you mean "fans"? If you had fifty of them, the power supply would just kick them all to the curb...

Anything is possible. However, having too many fans shouldn't be the issue since they draw minimal power—seven fans would only pull about 14 watts.
Can your Silicon Valley settings display the power supply voltages?
Check those numbers and report back. For instance, the 12V rail shouldn't drop below 11.40V.
It’s possible the 3V CMOS battery is dead or right on the edge; it might keep the time and date accurate while still corrupting other BIOS settings. It's hard to say where that threshold lies.
One system might run fine at 3.05V, while another starts failing at 3.20V.
Nova's battery sits between 3.3V and 3.4V. Normally, Silicon Valley chips should see around 5V.
Some motherboards can actually measure the battery voltage; check if yours can.
If you decide to swap the battery, perform a BIOS reset and select "Load Default Setup."
That ensures the BIOS and all hidden parameters are returned to their factory positions.
Personally, this smells like CPU overheating. Clean out the heatsink and make sure the Fan is actually spinning.

So, what was the final verdict?

darkowl72 said:Man, stop talking nonsense before someone actually thinks you know what you're talking about. What do you mean "fans"? If he had fifty fans, his power supply would just be struggling to keep them all spinning anyway...

I'm not just talking out of my ass here because I dealt with this exact same mess back when I was building a rig... he had a 400W power supply, and between the fans and all those other heavy hitters—like the GPU, the PCI cards, you name it—he was riding right on the edge of the limit, and one tiny spike in power and boom, it's game over...

It’s not 14W for 7 fans
Look, let's say a single fan runs at 12 Volts and 0.3 Amps, which is pretty much the standard, so that's 12*0.3=3.6W
That means 3.6*7=25.2W for 7 fans. It's straight-up math, not 14W...

It doesn't have to be me specifically, I'm just pointing out that maybe that extra 25W is what's screwing him over... I'm not trying to bark at anyone, we're just trying to fix the problem here, not play "who's right and who's wrong." Honestly, your post didn't help the guy at all, it just annoyed me...

John Turner34 said:Anything is possible... unless there are too many fans, though they draw very little power. Seven of them would only be about 14 watts.
I hope your BIOS can display the power supply voltages.
Check those and let us know. For instance, the 12V rail shouldn't drop below 11.40V.
It is also possible the 3V CMOS battery is dead, or right on the edge where the time and date stay correct, but everything else in the BIOS gets wonky... it's hard to say where that threshold is.
For some, 3.05V works perfectly fine, while for others, things start acting up at 3.20V.
The new one shows 3.3 to 3.4V. Ideally, Silicon Valley chips should sit around 5V.
Some BIOS/motherboard combos can actually measure the battery voltage; check that if you can.
If you end up replacing the battery, make sure to perform a BIOS reset and "Load Default Setup."
That ensures the BIOS and all hidden parameters are reset to their standard positions.
Personally, I suspect high CPU temperatures. Clean out the heatsink and verify that the fan on the cooler is actually spinning.

Let us know what ends up happening.

So far, I have followed the advice above. I am running the case with the side panel off for now. I don't think dust is the culprit since I clean it at least once a week. As for the fans, I have configured them for proper airflow—one intake, one exhaust, and so on. If the issue persists, I will check the BIOS. Thanks for the input regardless.

Lawrence Barnes64 said:...
It isn't 14W for seven fans
If we assume a single fan is 12V and 0.3A—which is standard—that equals 12*0.3=3.6W
So 3.6*7=25.2W. That is the math for seven fans, not 14W...

It doesn't have to be my specific number; I am just suggesting that 25W might be the issue. I am not trying to rush into conclusions. We are here to solve the problem, not point fingers at who is wrong. Your post didn't help the guy, it just annoyed me...

What kind of fans are you running? What are their RPMs? Faster means more power draw... but then there's the noise. Most people opt for 800, 1000, or 1200 RPM to keep things quiet.
Alternatively, swap out a 4W fan spinning at 2800 RPM for one at 1000 RPM; you'll cut the power draw by three.
Standard fans today usually pull between 0.35W and 1.2W (for 80-120mm models), depending on how quietly they spin.

John Turner34 said:Hopefully that Silicon Valley can show you the PSU voltages.
If it does, let us know what you see. For instance, the 12V rail shouldn't drop below 11.40V.

I thought I had this sorted, but I was mistaken. I checked the Silicon Valley today and snapped a few photos. Regarding the voltage and power supply, everything looks fine from what I can tell; these shots were taken after the PC had been running for about three hours (CPU Status, Memory status, System status). However, I think I found the culprit in the settings—under "Power Loading", it was set to "Auto". After reading the "Description", I switched it to "Enabled". Hopefully, that does the trick...

You found it!
What else is there... I guess you aren't exactly pushing this PC to its limits. :-)
Voltages look fine.
Good luck. Hopefully, the issue is actually fixed.

John Turner34 said:Good luck, hopefully the issue is sorted...

The fix only held for a few days before it shut down on me again last night. I'm honestly not sure 🤷 what's going on. I’m considering a fresh installation of Windows; maybe that would clear things up since I haven't done it once since I bought the machine. My main concern is all the data I need to save, and I just don't have enough storage space to back everything up right now...😢

Tell me, does it shut down so cleanly, as if you actually pressed the power button on the case?
You can tell by how Windows boots up. Does it start up normally?
If it boots up perfectly fine, I'd say the contact on the button itself is faulty, causing it to trigger on its own. If that's the case, it should also be turning itself back on randomly.

Check all the cables inside the case to ensure nothing is causing a short circuit. Also, check the power connector from the PSU to the motherboard. Is there a solid connection? Unplug it and plug it back in; it might just be some oxidation...

If it reboots, you’re likely looking at a BSOD—could be a software conflict like a buggy driver, or hardware issues like a faulty RAM stick. If the whole system just cuts out completely, it sounds like you need a new power supply. Just to rule out the basics, try plugging it into a different outlet or a different power strip first...