HaLO 2 Master Chief Armor: Helmet fans
After one night at Halloween, I discovered the helmet got hot FAST. The faceplate also fogged up.
Using instructions from jedi-academy.com I was able to install two 5v computer fans behind the "breather hoses".
http://www.jedi-academy.com/stormtrooper_helmet_fans.html
I have next to no experience with wiring but this was very easy. The second night went much better as I could hit the fans for a few minutes to cool down!
I finished out the interior with fun foam to cover some of the less attractive construction and cable tubing to hide the wires.