Although Raspberry Pi is a cool computer, keep it truly cool with a dedicated 5V, 40mm square fan. Ideal when you’re running it near 100% load all the time. Mounts to our Raspberry Pi S.A.F.E. (for B+ and V2) top plate (4-40 x 5/8″ bolts & nuts not included).
We’ve successfully used the onboard expansion port header to power our fan installations. Lift the retainer tab on the ground (black lead) and pull it out, and plug the connector (with the remaining red wire) to the corner-most pin. The ground pin can be then mounted to the pin 2 spaces down from it to give you a solid 5V for the fan.
Note: It’s always better to run the fan from a separate power supply, and this hack works best with a strong 5V 2A power supply feeding the Pi.