After 15 months use my PC wont pwer up. I checked the power supply by shorting the green/black pins and the fan turns on. I connected the PS back to the MOBO (using 24 pin connection) and the CPU fan also turns on. As soon as i connect the 4 pin 12V supply cable none of the fans work. I have all the Hard drives, disk drive disconnected btw. Any ideas why the power is lost when the 12V/4pin connector is added?