I don't recall that the IGN1 or "run" wire goes to the starter relay, only the IGN2 "start" that only gets power while cranking. The upstream side of the ballast resistor is the easiest place to access IGN1 (blue wire, I recall). However, I doubt that you want to pull all the fan current thru your key switch, since that might melt that circuit. Why not run the fan relay off BATT+. That will allow it to run when the engine if off, but many cars do that for good reason, so it won't boil over after you shut down.
