PC Shuts Down Randomly

My brother's PC shuts down with no warning, and no pattern to speak of (shut down twice in 3 hours one night, then went 4 days without doing it). This PC was working fine for 6 months after being built, this just started happening out of nowhere. We've troubleshot just about everything we can think of to no avail:

Replaced the Hard drive
Replaced the power supply
Changed the surge protector
Plugged into a UPS
Checked the RAM (even used a new 4gb stick for a day, on its own. it still shut down)
Replaced the CPU cooler
Took it to a local PC repair shop (twice)
Stress-Tested the GPU (Even swapped the GPU with his old one)

Please help, we're not sure what else can be done and we're getting desperate. This PC has cost us so much money already, and we just want to get it working again.

PC Specs (if it helps):

AMD AM3+ FX 9370
AMD 990FX(AM3+) MoBo
EVGA GeForce GTX 960 4GB
G.SKILL Sniper Series 16GB (2 x 8GB)
Cooler Master Hyper 212 EVO - CPU Cooler
Corsair CX850M PSU

Discussion is locked
Reply to: PC Shuts Down Randomly
PLEASE NOTE: Do not post advertisements, offensive materials, profanity, or personal attacks. Please remember to be considerate of other members. If you are new to the CNET Forums, please read our CNET Forums FAQ. All submitted content is subject to our Terms of Use.
Reporting: PC Shuts Down Randomly
This post has been flagged and will be reviewed by our staff. Thank you for helping us maintain CNET's great community.
Sorry, there was a problem flagging this post. Please try again now or at a later time.
If you believe this post is offensive or violates the CNET Forums' Usage policies, you can report it below (this will not automatically remove the post). Once reported, our moderators will be notified and the post will be reviewed.
- Collapse -
What's left?

Case, motherboard and CPU? Did you try the usual leave the case cover off and point a fan at the open PC?

- Collapse -
Case and CPU Ruled Out

We've tried running with the case open and a fan on it, and we think we've ruled out the CPU. If it was an error with the CPU, shouldn't we be getting some type of error? Like a BSOD code or a MoBo beep?

- Collapse -
Not always.

In the past month I've had a few machines with odd HDD failures that resisted diagnosis by testing. That is, both drives passed the maker's diagnostics yet when I cloned the drive to a new drive the issues vanished. (and yes the old drives were Seagates.)

The PSU looks like a good model but you have the usual AMD motherboard and CPU. That is, around my shop buddies we see those a lot. We're starting to dislike those models. That is the client will insist it fail a test yet when we replace CPU and motherboard the problem often vanishes. Of course the client wants us to figure out if its one or the other but given the cost of doing that, we would be giving them a much higher repair bill.

What to do?

- Collapse -
Checked for Malware?

If so, what was used?

- Collapse -

We used AVG to scan. Scans were and are run nightly.

- Collapse -
I'd add MalwareBytes (free version)

I just checked one of my systems. The antivirus didn't find anything, then MalwareBytes forund 132 PUPs. It usually takes 20 min. or less to run.
Good luck.

- Collapse -
Installed and Updated

I'll post results when he runs a scan with MalwareBytes.

- Collapse -

The only thing that was found was OpenCandy - which isn't malware. It's an advertising plugin. Anything else it could be?
- Collapse -
If it's something on motherboard

you may never see any indication of it. Years ago capacitors were burning out easily and also easily seen, but that "capacitor plague" is past on the newer motherboards which almost all use the better solid type capacitors. Other than having a second computer you can test each part on, one at a time, or something obvious seen on motherboard, not too much you can do more than you have.

It still could be an overheating processor, so changing the thermal paste and making sure that heavy heatsink is set solidly is what I'd try now.

CNET Forums