This morning, I turned on my computer and my power supply fan went straight to high speed. It stayed at high speed for 3-5 minutes. After 3-5 minutes the fan went back to normal, low speed. Normally when I turn my PC on, the graphics card fans do a quick full speed burst and that is it. I took the power supply out of the case and inspected everything, all the connections were solid and there didn't seem to be any dust accumulation. I then experimented with the eco mode switch and it seemed to only recreate the issue when eco mode was on. Mind you, I have a 1000 watt, Platinum, Supernova power supply and the max power usage of my setup is only about 475W. There is no way I'm straining this PSU. I've never heard the PSU fan once before this time, even when my graphics card was under high load. This seems to only happen when the pc is off for a couple of hours and the room is cold(under 60 degrees Fahrenheit). I can only assume that it has to do with the cold temp in the room, as that is the only variable that changed when this issue began. After first startup and allowing the pc to reach normal operating temp, the psu fan doesn't turn back on during startup. Any ideas? Should I send it in for replacement?

The 1000W Platinum series units (as well as many others) come with an EVGA PSU Tester in the box that fits on the mobo 24-pin connector for stand-alone PSU testing..Instructions are in the user manual..If you've lost the tester, then use the 'Paper clip test' to jump PS_ON and COM (Ground) as linked to above..But it sounds like the ECO Mode is faulty (wouldn't be the first time) and an RMA through EVGA or the retailer you bought it from would then be in order.