Check out Summit...get a Derale controller...it comes with a sender unit and is adjustable...there is also an override "on" connection that can be wired if you have AC or just want to run an override switch like I do.
My controller works very well to run the fans - adjusted to switch on around 190 and drops it to under 180 easy, then turns off....neat!
I run both fans of the controller.....works well. Most of the time when you're moving, you don't need the fans to be running anyway.