No, A scan tool is just that. It's main function is to scan and veiw data. Simply having it re-programed will not work either. You actually have to modify the software withen the ECU with a Tuning suite. There are sevral sponsers that offer mail order services. You can also buy your own Tuning equipment and do it your self. EFI Live and HP Tunners are the 2 most popular ones that work well and offer alot of support.

 

When you guys are measuring the radiator are you measuring just the core? I just bought a 04 Sierra SLT and need to do this swap ASAP, my fan clutch is weak and needs to be replaced.

My core of my radiator was around 29", from end tank to end tank was close to 34"..

By what I have read I should have a 31" but can someone confirm the way you are measuring to determine this for sure?

Thanks,

Jarod

 

Great write up but one thing where on the radiator do you measure to determine if its a 28" or a 34". If i measure inside the radiator ends (just the core) its 28" if i measure from out side to outside its approx 34" any help. Thanks

 

i did the install exactlly. when i hook up battery fans come on high, right side only. is this a problem or will the tune change it? is pin #42 grounded all the time now till the tune?

 

I just changed mine, had the same measurements, that is the smaller radiator. You need to change to the larger radiator if you want to use truck fans.

You have the blue trigger wire grounded only then. If you ground the green trigger wire you will get both on at low speed. If you ground both the green and blue trigger wires you will get both fans on at high speed.

Once you pin the computer and program it this will all take care of itself.

While I was waiting on my tune I twisted the green and blue trigger wire together and ran it to a switch in the truck and switched the fans on when I was driving and turned them off when I parked the truck.

 

well after re-reading the thread and mulling over the wire diagram i have some questions lol.


#1 it says in the thread that the ac relay controles the high speed (one fan high) and the computer controls the low speed (two fans on 1/2 speed), first that means you would be moving about the same amount of air no mater if its on low or high, so do trucks from the factory only have the "2" speeds

#2 what does the factory turn on when the ac is activated (both high, one high, or both low) and what does it turn on due to the coolant temp (im guessing that's how they would do it)

#3 wouldn't it make more sence to have the ac turn on one full speed(or both on 1/2speed and then have the computer/ temp turn on both on full or is there something im missing about how it turns on the speed

 

The way it works when it is wired up is as follows:
-If the AC is on,(and coolant has NOT reached 209 yet) one fan turns on
high speed.
-If the AC is off, both fans turn on at low speed when the coolant gets to
209 (or whatever temp you have them set to turn on at).
-If the AC is on AND the coolant is up to temp, then BOTH fans will run on high.

So in a nutshell, on wire triggergs one fan on high, one wire triggers both on low, and both triggers together trigger both fans on high.

 

Hey thanks for doing that original write up man. I wanted electric fans bad but did not want it half assed in any way and couldn't find a real good way around it until I found this thread.

I got an entire front end harness from the junkyard for $30, got a set of used fans for $100, and bought a brand new 34" radiator for $150. It was well worth it to have a fully computer controlled and completely factory looking setup.

I have a 2004, so I was able to get the truck tuned to control it all.

 

Instead of useing the AC clutch to control the one speed, you can plug it into the PCM and the PCM controls both low, high, and AC on a 99-02 PCM.

 

Great write up, helped me a lot with my install, just waiting on a tuned pcm now, I have two questions though as I'm not done just yet.

What do you do with that first plug on the harness? I have an 04 SS and don't have anything for it to plug into.

The two black wires at the end of the harness, those are just grounds right?