I've ran into a issue with my computer that it does no longer reach POST, but simply powers on for a fraction of a second and powers off. But this is not always, some times it boots just normally and it works as it should, no issues with not enough power or anything. But as soon as I turn it of, I can not turn it back on, but then again at some random point it just powers up again, and resumes normal operation.

If I disconnect the 8pin ATX connector from the motherboard, it powers up, fans and disks spinning normally until I power it off again. So this problem only happens when ATX is connected, which seems odd, I normally always saw this kind of an error if ATX was not connected, but here it's the exact opposite.

It also does not emit any sound on the buzzer, except the normal beep, when it powers up normally. I have already tried:

• Remove graphics card
• Remove one and/or all RAM sticks
• Disconnect everything non-essential, even hard drives
• Clear CMOS

I have not yet tried to remove all components and tried to boot everything outside of the case, because I did not have the time to disassemble and bleed the water loop. However, I can confirm that nothing is stuck underneath the motherboard, not is any of those brass raisers touching the board where it should not.

Specs:

• Gigabyte GA-970A-UD3

• AMD FX6300

• ATI HD7850

I think this should be enough for this issue.