GPU fans do not fully spin up. PSU problem?

[MajMalfunction]

I came home one day to find that my PC wasn't responding and my new GPU's fans weren't spinning. First impressions said the GPU was the problem. I removed and tested the fans with a jumped spare PSU, and found that they worked. Just for kicks (or despair that my new GPU now a paperweight waiting to be RMA'd), I reinstalled it and tried it again to see if it was a fluke (it wasn't).

 

During POST, my GPU's fans spin up, but stall before the system's bootloader takes over. Normally, this causes the POST to fail. Spinning the fans up manually lets me boot into an OS, and the fans spin as expected, and everything works like it should. My BIOS's Hardware Monitor reads the +12V rail as 11.900V and the +5V rail as 4.875V (both in spec). I also tried CPUID's HWMonitor, which told a different story (unreliable as SW solutions are, but it was at least consistent across multiple boots, as was the BIOS reading).

 

Now I'm suspect of my PSU. I don't have access to another PCI-e card or another working PSU, but my PCI-based wireless NIC does work. With that said, have I done everything I can to narrow down the possible causes?

HWMonitor.txt

[MajMalfunction]

Bump and update: The system boots with the GPU installed, but the fans only spin for a little while during boot depending on which PCIe 6-pin cable is plugged in. I think this narrows it down to the PSU. I'm thinking about applying for an RMA or buying another PSU, whichever is cheaper.

[jameyscott]

I would go ahead and RMA the PSU. Is there any chance you have a DMM (Digital Multimeter) that you could test the connections with to make sure that you are truly getting the voltage the GPU needs?