Unexpected Shut Off After Start Up

[kyuubigaki]

Okay, so I have a computer that was custom built.
It worked fine for quite a while, however now it shuts off without warning.

I can turn it on, but within the next minute to 3, it will shut off. Occasionally I can actually login.
It's been down and out for about a month now, I've just now found the time to sit down and really work on it. I have noted that each consecutive time I work on it the time between start up and shut off shortens.
The Disk percentage in task manager reads and stays ridiculously high the entire time.

Last check clocked in at 1 minute 24 seconds from login to unaided shut off.

Motherboard - Gigabyte GA-970A-DS3P
OS - Win10
Cooling - Asetek LCLC
PSU - Raidmax 1000W 80 Plus Bronze
CPU - OEM AMD Fx-8320 3.5GHZ Eight Core 125W
Anything else needed I can supply.

Thank you very much for any and all suggestions.

EDIT: On further inspection, I noticed earlier mention of a green wire that should be attached the PSU. I had the red and yellow, but the green was missing. I've now noticed it's unattached, inside the PSU. Could that be part of the issue?

 

[Dark Lord of Tech]

Probably the PSU , Raidmax are very very poor quality.

 

[kyuubigaki]

Probably the PSU , Raidmax are very very poor quality.

Would there be a way to test that?
And if it is the PSU, might you have a suggestion for the replacement?

 

[Dark Lord of Tech]

Sounds like a power issue , sudden shutdowns are usually power or heat related and the board is a poor match for a 125w CPU it only has a 4+1 power phase design.

http://www.hdtune.com/
Also run HDTUNE to check your disk health.

 

[kyuubigaki]

Sounds like a power issue , sudden shutdowns are usually power or heat related and the board is a poor match for a 125w CPU it only has a 4+1 power phase design.

http://www.hdtune.com/
Also run HDTUNE to check your disk health.

At the time of being built it was pretty compatible... admittedly this is a bit older. About 3 years now?
Something I just noted, I've seen mention of a green wire that should be connected to the PSU, right?
It's inside the PSU, not connected to anything.
I'm not sure if it's meant to be that way or simply an oversight by the people who put it together.

 

[Dark Lord of Tech]

Raidmax overall is a bad idea in any setup.