Mess around with it. Thats how I worked it out. Its 5V, not going to do you any harm.
Ok, so I followed the fan diagram on the forums and tried it on the pci fan and it didn't work. So I tried a few different combinations to no avail. Any way I can tell the ground from the power wires? Thanks!
TBH thats probably against what everyone will say, dont mess with electricity etc, but like I say, worked for me