Here is the size of the fan compared to the radiator. This is the reason I'm heavily considering the MB fan. A large percentage of the radiator (specifically under the inlet) is not covered by the shroud and hence isn't cooled by the fan. Big bummer.



Here are the low and high speed relays. Taken from a Chrysler Concorde, they are 40 and 70 amp, respectively.



And here is the small Hayden controller. Not the best controller in the world, can only do single speed, but it is effective, and I will eventually be using a homemade PWM controller in conjuction with my Megasquirt ECU to control my fan.



Without spending a boat load on a dual speed controller, this is the next best option. I have the two speed relays wired in such a fashion that the fan never receives voltage on both legs (low and hi) which is a must, or you'll get to see just how much smoke they put in these things at the factory.

I have a small switch on the underside of my dash that is used as a selector. It normally sits in the Low setting, and when the temperature probe of the fan controller hits 180, the fan kicks on low. If for some reason I notice the temp continue to climb (haven't yet), I hit the switch, it kicks off the low speed relay and on the high speed relay.

I've also got this wired to constant power, so when I park the truck and get out, it continues cooling the radiator down until the temp probe says to stop. Nice little feature that you'll notice newer vehicles have.

Shoot any questions you have