I wrote this up in Feb. so I might have gotten a little rusty on things, feel free to ask q's and i'll do my best.
Grabbed a 2-speed Taurus fan from the local junkyard for $15, out the door.
First thing i did was all the wiring in the truck, this is the schematic that i used to do so. What i wanted was the high speed to come on when my a/c was turned off. To do that, however, easiest way i found, was to add a third relay.
Relay Control Wiring
For the switched 12v
source i used the Black w/Light Green tracer wire that is located in the HVAC control.
For the 'A/C Request'
power, i used the solid Purple wire, also located in the HVAC controls. Not
the Purple w/Yellow tracer wire.
For the Coolant Temp ground
I used a adjustable switch that controls the ground for my relay. Picked it up from the local Advanced auto parts for $17.
I wanted to use a toggle switch for the 'a/c request' circuit so that if i was cruising down the highway for an extended time, i could go ahead and turn the 'high speed' off. Thanks to the speed of the air passing through at cruising speeds.
High speed power circuit got nothing but 10gauge (can hold a constant 55a, safetly. Yes, overkill..) wire. It has a 30a circuit breaker which has no problem running the fan.
Low speed i am running a 20a fuse and 14ga wire (can hold consistant 32a, safely)
Relay control circuits got 16ga wiring
Relays I am running are rated for 70amps (aka HUGE/overkill, but not a bad thing). I picked those up from the junkyard as well as the connecting sockets.
My circuit breaker is located in the stock fuse box, and the low speed is just an inline fuse holder which is not in the right slot there
IDing your fan's wires
Incase you have different wire colors on your fan, you'll need to get an ohm meter out and check the resistance to figure out your wires.
Black = Ground
Blue + Black = High speed (low resistance)
Brown w/Yel + Black = Low speed (higher resistance)
Now my fan mounting isn't the most beautiful work of art. It is functional however. Which is what most of us care about. I removed the stock fan clutch (I removed my clutch by taking a long crescent wrench, snugged it to the nut, and smacked the end of the wrench 3x clockwise and it broke the fan loose from the water pump) and shroud.
Laid the shroud out and the fan. I found my best method was to mount the fan lengthwise across the radiator in the stock shroud, and cut accordingly. Problem with the taurus fan in the stock shroud, is the hole for the clutch fan is huge.
I got a $5 sheet of 26ga steel from Lowes, and a pair of tin snips. With the fan laying in the stock shroud i made templates of what size plates i needed to cover the open areas with cardboard and a sharpie. Traced it on the steel, and cut it out. Fairly simple, i've hardly worked with metal..not hard to do. I then just pop riveted the steel to the stock shroud to keep it there.
To seal the entire fan to the shroud so no air 'sneeks' in between the fan and radiator, i used 1/2" foam tape from lowes. Look in weatherstripping. Works wonders.
To mount the fan in place in the shroud i got two 10" pieces of 1/4-20 All thread, and a pack of 1/4-20 nuts. Drilled through the stock shroud and the taurus fan and used four of those to keep it in place. Adjusted it around using the nuts along the all-thread to where i wanted it. Snugged 'em down, its in there just fine.
Installed, stock bolts and all. Clears everything, and works beautiful
If there is interest i do have a few more pics i can fit in somewhere. Hope it helps someone