I bought a "kit" with an adjustable temperature setting so it will come on at what ever temp you want (within their pretty wide range), and will turn off when the temp drops so many degrees (10 I believe). They recommend you turn on the fans 10 degrees above the trucks thermostat rating. That kit came with either an insert into the radiator core sensor, or a screw into the cooling system temp sensor and relays (50 amp ratings) with wiring. It can run one or two fans, and will kick one fan on then the second shortly after. I bought the one I have off ebay for something around $50, then you buy which ever fan(s) you want.

Mine cycles on and off regularly once the motor reaches operating temp.

the only complaints I have with the controller I have is 1) The digital temp reads in degrees "C" rather the degrees "F". I had to do the conversion the day I set it. 2) It came without written instructions, you have to read the clearly printed wires to make the electrical connections. 3) The control is "water resistant", but not "water proof". It needs to be placed where it is protected from getting too wet. None of the complaints were much of an issue.