I've got an Antec Sonata Mini Tower with a 380 watt ATX12V power supply.
My PSU fan, and Fan only connections have died after randomly working for the last few days.
The 4 pin FAN ONLY (yellow & black 2 wire) connections don't work anymore - BUT I was able to plug my fans into the regular 4 pin connections. They're running at full speed, but at least they're running.
I can't seem to bring the PSU fan back to life...I had it working for a few minutes this morning by pure luck apparently.
I'm not sure what's wrong, the PSU isn't supplying power to the Fans like it should.
I would first seek warranty replacement before messing with it, if warranty is off then try testing the fan itself with another power source, 4 pin fan connectors are for speed controlled fans right? might be a faulty speed controller? Take a peek in the PSU maybe a capacitor went bad?