PSU Molex to 4 pin adapter won't allow computer to turn on.

[Al Scarpone]

I just finished building my second computer and I ran into a problem. My build is here: http://pcpartpicker.com/b/GGz#cx171965

The computer fired up right away with no problems except that the case fans did not work. The fans use molex cables which I wasn't happy with at the start. I found an old pair of molex to 4 pin adapters and tried using them but the case fans still would not work. Then I tried the psu adapters that came with my psu. I plugged the part into the psu where it fits and then plugged the molex fans into the adapter. I then plugged the 4 pin part of the adapter into the correct spot on the motherboard. The computer would not turn on. When I unplug the adapter from the psu and wait a few seconds and push the power button, the computer fires up. When I plug it back in, nothing. Does anyone know what the problem is? I have never used molex adapters and I could be doing something wrong. If pictures are needed, let me know. Could this be a wattage issue? I figured 500w would be plenty for this build...

 

[alexoiu]

You're shorting the board this way (if I've correctly understood).
With the adapters, you either connect the fans to the molex or to the 4 pin. Don't connect the 4 pin to th motherboard. Those headers on the motherboard provide 12V to the fans (fans that have a 4 pin connector can be directly connected to the motherboard and not to the power supply - this way, their speed is controlled, depending on the temperatures).
Now, why fans don't work when connected to the PSU molex? Fans or PSU issue.

 

[coastie65]

First, the PSU wattage is enough. How many case fans are you using? I checked out your Motherboard and found the CPU fan header plaus two others, on obviously for the rear exhaust fan and a four pin at the bottom that could be used for a front intake fan. If the fans themselves had a Molex connection, then you couldn't use the headers and would need adaptors. Even with the adaptors, one end should still plug into the headers.