i'm actually running my radiator fan off of a switch right now. the fan control relay is busted, checked w/ mercedes and chrysler, they want to charge 600$ to replace the unit...bloody hell. anyways, i'll take a picture of my setup, its really simple. Just using an inline switch under the hood till I get an aftermarket programable fan relay off of jegs for 50$. that damn radiator coolant warning light is always going to be there though..

Best to use heavy guage wire and a high-rated switch. I'm using the same size wire as stock (6 guage str) and a 50amp switch to avoid any under-hood meltdowns. 6str is pretty big, so not available at most autozones. go to home depot, you can pick up 7ft of 6guage and a 50switch for under 20$