I ran a Hayden cooler and a Hayden fan. I bought the cooler and installed it, but it wasn't cooling enough when sitting still, so I added a fan. It was about $65 for the cooler, and another $60 for the fan. I ran a standard Bosch-style relay, and I have it triggered off of the driver'* side fan. There'* a spot on that fan that'* easily accessible, and you can plug a spade connector right to the connector block on the fan. You'll see the exposed wire soldered on this block. It works for me, as when it'* hot enough for me to need the cooling fan (most of the time in Houston), I'll have the A/C on, which triggers both fans, thus turning on my trans cooler fan. The relay is about $5, and a Bosch relay connector is all of $1.50.
With that connector, cut the red wire off (not needed). Connect the black to ground. Connect the blue directly to the battery positive (I used a big ring connector). You may also consider adding an inline fuse. Connect the yellow to the positive wire on the fan itself, which on my fan is the black wire
. You would connect the other fan wire to a ground source. Connect the white to the power source that will turn it on, which in my case is the driver'* side fan. You could also rig the white wire to anything else that is 12+ when you want the fan on. This is the easiest way to make a circuit that doesn't involve tapping into another circuit and overloading it. You can see the white wire that comes across the radiator fans to the relay, and the relay itself to the left of the battery, creativly hung with a tie wrap.
I wasn't going for the cleanest install, just one that works. I could certainly hide the wiring better for an invisible install.