Question Pc shutting down and restarting

[Mikashimo33]

I've been having problems in the last few months with my pc.
At first I thought it was restarting but with some test and changes I found that it was shutting down and restarting.
I've changed the hard disk, the heatsink and removed a Ram and still was shutting down. At this point I thought it was the psu, so I started doing stress test but I didin't show up any problem with voltages.
I decided to connect a multimeter in a molex so I could check the voltages at any time even if it shuts down, I found when the pcs shutsdown the voltage drops to 1v and then start to escale until 12v again.

I want to know if this is 100% problem with the psu or there is any other component causing this issue.

Pcs Specs:

Motherboard msi b85m-e45
Hard disk Sata 1Tb
heatsink Cooler master
Cpu intel i7 4790
Gpu Geforce Nvidia 960 4gb
8gb ram hyperx ddr3
psu cougar 600w 80 plus white

 

[PC Tailor]

At this point I thought it was the psu, so I started doing stress test but I didin't show up any problem with voltages.

Stress tests are only an indicator of PSU problems, but aren't ever that accurate with PSUs.

I decided to connect a multimeter in a molex so I could check the voltages at any time even if it shuts down, I found when the pcs shutsdown the voltage drops to 1v and then start to escale until 12v again.

In the molex? The molex won't give any tangible readings that you could deduce from, as realistically you just want to see the major rail fluctuations under load, which really you can only do with either specialist gear or using software on the PC

Testing with a multimeter when the PC is off, and just booting the PSU only tests PSU voltages at idle.

If you were to use software however, such as HWInfo, and check voltages, and fluctuation on the 12V, 3.3V, or 5V rail that is out side 5% means the PSU is faulty.

psu cougar 600w 80 plus white

Cougar don't make many good quality units, so it depends what model line it is. So it certainly could well be PSU.
Random restarts can also be indicative of this. Not guaranteed though. Best way to test is to replace the PSU with a known working good quality unit and retesting.

But going off my knowledge, Cougar don't make many good qualtiy units, and most are poor from my understanding.