I've been getting alott of PM's about my fan install so I am trying my best to post what I did how its wired and what it looks like installed.
Here it goes:
On my 2002, Gen 3, 3.9LV6, I did this: I am not familiar with other years so if yours is not the same check into things before you get started.
I removed the lower half of the fan shroud completely and unbolted the top half of the should from the overflow and washer bottles and removed it also, removed the clutch fan, removed the factory electric ac fan, temporarily removed the overflow and washer bottles to fit the fan then reinstalled them over the new fan.
I installed 90-95 3.8Lv6 fan from a ford Taurus, its a 2 speed fan. I installed a temp sensor in the coolant passage to the heater core to turn my low speed fan relay at 195 wired a 2nd relay to the ac fan signal then to the fan.
I am defiantly pleased with the results, truck runs cooler, engine revs faster idles smoother. This free'ed up top end power for getting up to speed and merging on the highway with the V6. Other then that not much was noticed, motor seems peppier, but not more powerful. Seems not to be as sluggish with the AC on, and the AC is ICE COLD. I can't even put it on Max it just freezes you out in the reg cab! This has been on the truck now for a few months about 5000 miles no problems.
I made up some brackets from an aluminum strip I got at home depot to hold the new fan in place, I cut and bent the aluminum strips to bolt the factory ac fan locations on the radiator. I also got my 3/8 brass nipple and tee from home depot to thread in the 195 on 185 off sensor from summit (its a JET sensor for a GM car), got a (Jet) 180 degree stat from summit, and the 4000+ CFM Taurus fan from the junk yard $35, got the double pole single throw relays from http://www.waytekwire.com/. They are 40-50 amp relays (heavy duty Tyco's) I fit the relays and breaker into a 2"x6" radio shack control box. I also made a plate for inside the truck with 2 led's so I know when the fan is on low or high, I put it in the slot that houses the 4wd selector since I have a 2wd truck this spot was useless. I made the plate out of the aluminum lid that comes with the project box since it was extra. I just wired the LED's 12v lead to the output of the relays going to the fan, ground to a ground under the dash.
Remove alternator, and disconnect the heater core supply, hose take the fitting for that out of the manifold and thread in the brass 3" nipple in its place, then the 3/8 female tee, thread the factory fitting into the brass tee hook the heater core hose back up and thread the sensor into the top of the tee (may need to trim the hose a bit). Change t-stat while your there and put back together (make sure the tee is not in the way of the alt, reinstall alternator) I provided a pic but since taking the pic I have since changed this to the above method, the first time I did it I was using fittings I had laying around, while it worked fine it left me the issue of having to remove the alt to change the sensor if it were to go bad. The new way I can change it easily without removing the Alt. I originally had a 185 on/170off sensor in there but with the 180 stat the coolant never dropped to 170 so once the fan came on it would just keep running.
(remove old factory ac fan and cut wires off fan after the connector)
Wire high speed relay as follows.
12v off battery to 50A fuse or breaker
Off breaker to 12v nomally open pin on relay
12V relay coil signal to green factory fan wire
Relay ground to black factory fan wire
run 12v out to high speed fan wire on Taurus fan.
Wire low speed relay as follows
Hook the 12v normally open input of this relay to the nomally closed pin of the high speed relay
12V relay coil signal to an Ign source or to the battery (if on ign fan will turn off when you turn off the truck, if on battery fan will run until it cools down to temp sensor cut off limit usually 185 for a 195 turn on sensor, I wired mine both ways with a switch to select the function I wanted)
run 12v positive "out" to low speed wire on fan.
Run the coil "ground" of the relay to the sensor you installed in the coolant passage, the sensor will supply the relay with a ground to engage the relay to turn on the fan when the sensor gets to the correct temp.
Doing this like I did allows everything pretty much plug and play so you do not really modify the factory wiring other then the fan wire but it keeps you from touching the main engine harness and you can run the bigger fan same as the factory controls. The other benefactor is if for some reason you loose your low speed relay or sensor to turn the fan on low, the PCM can still turn the fan on for high temp at 210 to keep you from overheating.
-Ed
Here it goes:
On my 2002, Gen 3, 3.9LV6, I did this: I am not familiar with other years so if yours is not the same check into things before you get started.
I removed the lower half of the fan shroud completely and unbolted the top half of the should from the overflow and washer bottles and removed it also, removed the clutch fan, removed the factory electric ac fan, temporarily removed the overflow and washer bottles to fit the fan then reinstalled them over the new fan.
I installed 90-95 3.8Lv6 fan from a ford Taurus, its a 2 speed fan. I installed a temp sensor in the coolant passage to the heater core to turn my low speed fan relay at 195 wired a 2nd relay to the ac fan signal then to the fan.
I am defiantly pleased with the results, truck runs cooler, engine revs faster idles smoother. This free'ed up top end power for getting up to speed and merging on the highway with the V6. Other then that not much was noticed, motor seems peppier, but not more powerful. Seems not to be as sluggish with the AC on, and the AC is ICE COLD. I can't even put it on Max it just freezes you out in the reg cab! This has been on the truck now for a few months about 5000 miles no problems.
I made up some brackets from an aluminum strip I got at home depot to hold the new fan in place, I cut and bent the aluminum strips to bolt the factory ac fan locations on the radiator. I also got my 3/8 brass nipple and tee from home depot to thread in the 195 on 185 off sensor from summit (its a JET sensor for a GM car), got a (Jet) 180 degree stat from summit, and the 4000+ CFM Taurus fan from the junk yard $35, got the double pole single throw relays from http://www.waytekwire.com/. They are 40-50 amp relays (heavy duty Tyco's) I fit the relays and breaker into a 2"x6" radio shack control box. I also made a plate for inside the truck with 2 led's so I know when the fan is on low or high, I put it in the slot that houses the 4wd selector since I have a 2wd truck this spot was useless. I made the plate out of the aluminum lid that comes with the project box since it was extra. I just wired the LED's 12v lead to the output of the relays going to the fan, ground to a ground under the dash.
Remove alternator, and disconnect the heater core supply, hose take the fitting for that out of the manifold and thread in the brass 3" nipple in its place, then the 3/8 female tee, thread the factory fitting into the brass tee hook the heater core hose back up and thread the sensor into the top of the tee (may need to trim the hose a bit). Change t-stat while your there and put back together (make sure the tee is not in the way of the alt, reinstall alternator) I provided a pic but since taking the pic I have since changed this to the above method, the first time I did it I was using fittings I had laying around, while it worked fine it left me the issue of having to remove the alt to change the sensor if it were to go bad. The new way I can change it easily without removing the Alt. I originally had a 185 on/170off sensor in there but with the 180 stat the coolant never dropped to 170 so once the fan came on it would just keep running.
(remove old factory ac fan and cut wires off fan after the connector)
Wire high speed relay as follows.
12v off battery to 50A fuse or breaker
Off breaker to 12v nomally open pin on relay
12V relay coil signal to green factory fan wire
Relay ground to black factory fan wire
run 12v out to high speed fan wire on Taurus fan.
Wire low speed relay as follows
Hook the 12v normally open input of this relay to the nomally closed pin of the high speed relay
12V relay coil signal to an Ign source or to the battery (if on ign fan will turn off when you turn off the truck, if on battery fan will run until it cools down to temp sensor cut off limit usually 185 for a 195 turn on sensor, I wired mine both ways with a switch to select the function I wanted)
run 12v positive "out" to low speed wire on fan.
Run the coil "ground" of the relay to the sensor you installed in the coolant passage, the sensor will supply the relay with a ground to engage the relay to turn on the fan when the sensor gets to the correct temp.
Doing this like I did allows everything pretty much plug and play so you do not really modify the factory wiring other then the fan wire but it keeps you from touching the main engine harness and you can run the bigger fan same as the factory controls. The other benefactor is if for some reason you loose your low speed relay or sensor to turn the fan on low, the PCM can still turn the fan on for high temp at 210 to keep you from overheating.
-Ed
