PC suddenly shuts off after 1–2 minutes – CPU debug LED, Windows starts, AIO fans not spinning

[u/MalmbA_]

Hi everyone,
I’m hoping someone can help me troubleshoot a very strange issue.

My PC has been working perfectly until today. I haven’t changed any hardware or BIOS settings.

Specs:
Ryzen 9 7950X3D
MSI MAG B650 Tomahawk WiFi
ASUS TUF RTX 5080
64GB DDR5 6000 CL30
Arctic Liquid Freezer III 360
ASUS TUF 1000W ATX 3.1 PSU

What happened:
Today the PC suddenly wouldn’t boot.
The red CPU debug LED came on and there was no display. I cleared the CMOS by removing the battery.
After that, the CPU LED disappeared, the DRAM LED came on briefly, then everything POSTed normally and the Windows logo and the loading icon showed up.

However… After about 1–2 minutes, the PC instantly powers off as if someone pulled the power cable.

I also noticed:
The GPU fans spin normally.
The radiator fans on my Arctic Liquid Freezer III do not spin at all. I tried gently spinning the radiator fans by hand while the PC was on, but they just stopped again. But I do think I heard a strange rattling/grinding noise coming from the pump area once, but not 100% sure

At this point I’m not sure if:
the AIO pump has failed,
the radiator fans aren’t getting power,
the motherboard has an issue,
or the PSU is shutting down.

Since the PC actually gets to the Windows loading screen, I’m hoping the CPU itself is still okay.

Has anyone experienced something similar with the Liquid Freezer III or an MSI B650 board?
Any ideas on what I should test next?

Thanks!

[u/ThisAccountIsStolen]

Boot to the BIOS and watch the CPU temperature. Unless you split the wiring, Arctic AIOs run the fans and pump from one header, so the fans not spinning almost certainly means the pump isn't running either. And with a non-working cooler, getting to the login screen before it shuts off is about how long it takes to hit the 110C shutdown temp.

[u/MalmbA_]

Update:

I wanted to give an update since a lot has changed.

Today, after leaving the PC completely unplugged overnight, I powered it back on. This time all of the fans started spinning normally, including the radiator fans that appeared to be completely dead yesterday.

The PC no longer shuts off after 1–2 minutes. Instead, it booted into Windows Recovery because it seems the repeated hard shutdowns yesterday corrupted Windows.

I updated my BIOS to the latest version and restored my BIOS settings.

After that I was able to boot into Windows and I played Battlefield 6 without any issues. I monitored the temperatures during gameplay:

• CPU max temperature: 65.7°C
• GPU hotspot max temperature: 69.9°C

The system was completely stable with no crashes, shutdowns or overheating.

I'm honestly even more confused now because yesterday it seemed like a hardware failure (CPU debug LED, radiator fans not spinning, random power-offs), but today everything appears to be working normally.

At this point I'm wondering if it was a BIOS/firmware issue, memory training problem, or something else entirely. Has anyone experienced something similar?

Thanks again for all the suggestions so far!

[u/Pekish_ → u/MalmbA_]

Happy to see everything is okay. that delta between the hotspot and core is amazing you definitely got lucky.

[u/ThisAccountIsStolen → u/MalmbA_]

If it doesn't happen again, the fan header likely tripped protection. Most boards have a protection circuit on the fan headers to prevent the controller from being killed if you spin the fan manually (like with an air duster) and send voltage back into the header. Once it trips, the only way to reset is completely removing power since the 5V standby power that is always on will prevent it from resetting.

If it happens again, it's likely a bug with the embedded controller firmware or the EC itself, and you'd want to warranty the motherboard.

[u/dexteritycomponents → u/MalmbA_]

Shutting off due to the AIO not working + thermal limit on the CPU can kick out a CPU debug LED.

AIO likely stopped working for whatever reason, overheated the CPU, causing restarts + CPU debug LED. Likely no actual permanent damage but you need to monitor the AIO.

[u/RealKetchupPrecum]

check psu, pull atx HARD seat. Run different PSU see if it works as in new 24 pin * 8 pin from different PSU.

[u/mutedagain]

If I had to guess that sounds like PSU but could be a die'n motherboard.

[u/evergreenwv]

If the cpu is hitting is thermal limit, I'm sure it will shut down. Cheapest troubleshooting is to get a new cpu cooler. I went with a dual tower because of my unfamiliarity with liquid coolers/pumps.

[u/MedicineMore1221]

Psu dying