I would have assumed it had to be extended? So the switch can reach to where you want it?

I was looking for a write up on how to do it to see where people chose to put the switch and such

 

You would have to do more than cut one wire and put a switch in. The fan is triggered by a temperature sensor, which actually switched the ground or (-) connection of the circuit. The (+) connection is constant. You would have to cut the black wire on the fan motor and attach that to one side of the switch. The other side of the switch would be a direct ground (-) connection. Splicing into any of the green (-) wires in the existing wiring harness would suffice, or you could run a wire straight to the (-) terminal of the battery. The resistance is negligible so you can attach any length of wire that you'd like to the recently cut black wire and to the other side of the switch so you can position the switch wherever you'd like.

Good luck and let me know if you have any questions or trouble.