In many cases, users doing troubleshooting have a situation where there is no apparent power to any portion of the system. They often wonder how they can test the PSU to see if it is working. Short of having a proper PSU tester, you can use this method to do a "quick n dirty" test to see if the PSU will spin up and power the 12v rails.
1. Disconnect the PSU from ALL components in the system.
2. Hook 1 or more cooling fans to the PSU to give it a load. (You can use other items such as HDs but, I recommend using something cheaper and less fragile like a fan)
3. Get a small piece of wire, paper clip, or suitable object and short the 2 pins illustrated below. The voltage present is a very low signaling voltage so no worries of being shocked.
The fans should spin right up. This is not a bullet proof test but, it will let you know if your PSU is powering up properly.
We have also added a video tutorial demonstrating how to perform this test.
PSU TEST VIDEO IN CORSAIR CINEMA