Is my GPU dead or is my PSU not powering it right?

[ImFelix]

So I was playing Overwatch on my PC and suddenly it crashes. I couldn't get it to display any image on the monitor when I booted the PC on so I had to boot on safe mode and uninstall the graphics driver back to the Intel HD basic one. After that it booted normally.

I open my PC Case and see that my GPU has 1 fan not spinning out of the 2 (R7 370 4GB). Every other fan on my rig is spinning. I unplugged my GPU and cleaned it from any bit of dust it had (it was sitting there collecting dust for 2 years, I'm such a bad person) and made sure to plug it correctly but the very same scenario happened (only 1 fan spinning).

What I get from this is that the GPU is getting power from the PSU at the very least. If it was just a damaged fan then it would still work but only get hotter and hotter (as the fan is not working). So my question is, is it my GPU being dead (only 2 years old, but constantly dirty as fk) or my PSU dying (I get lots of blackouts here normally)?

Motherboard: GA-970-UD3

 

[DRagor]

Certainly there is some problem with GPU. Non working fan could be caused by such a simple thing as disconnected fan cable inside GPU, or it could show bigger problem, but there's nothing that faulty PSU could do to make one fan work and other don't. But it is also true, that just a fan failure would not give you no-display issue in Windows (I get it that you were getting display in BIOS though?).
So what will happen if you try to install GPU drivers again? Will the install fail? Or it works, but you get no display after reboot? The former would indicate GPU is failing. The latter might too, but it could be just a problem with driver (so I would try different version of drivers in this case).
Either way, to find definitive answer, whether the issue is caused by PSU of GPU, you would need to test with different units - either your GPU in another machine, or different PSU in your machine.