I have tried following the advice here and here, and connected the black outside wire on the fan to my PSU -V, and then connected the next, red wire on the fan to my PSU +V. Yellow and green wires are left disconnected; I want the fan to run at full speed. The fan powers up just fine in this configuration, but spins in the wrong direction (it blows air down).
I'm using this little project as a learning tool to understand basic electrical theory. My simplistic guess was that I had the wires backwards, so I switched the red and black fan wires (black to +V and red to -V). When I turned the system back on the fan didn't start up at all. I tried cutting and restripping the wires and then switched them back and forth a bit to make sure I didn't just have a bad connection, but it works every time in configuration 1 and never in configuration 2. I'm a little confused as to why.
Why is this fan spinning backwards, and how do I wire this CPU fan so that it spins in the right direction?