Or, if you're an electronics wiz, you can create a temp sensor enabled, varied resistance circuit to have full control from the cockpit. Even someone with enough electronics knowledge of the engine wiring could do a two way relay connection and use the fan switch as the trigger to go from 8V to 12V.

http://www.bnmotorsports.com "And I will strike down upon thee with great vengeance and furious anger those who attempt to poison and destroy my CEG brothers. And you will know I am the Moderator when I lay my vengeance upon you."