2 relay== one fan used for cooling (on the high setting), one fan for the A/C (on the high setting). Two fans on high for A/C and cooling.

3 relay== two fans on low for cooling, one fan on high for A/C, two fans on high for A/C and cooling.

You get more even cooling across the radiator with the 3 relay setup when not using the A/C.

Hope that makes sense.

=Dave

 

How cheap you want to be? I got my LT1 fans for $75. Bought the wires at Auto zone for $30 and went to work. I have each fan wired independently using 10g wire to the 30 amp relays and 16g to the switches mounted in the truck. One switch is wired to be powered up when the key is on and the other is when ever I need it regardless of whether the ignition is on or not (need to change that since I ran the batt down the other day LOL) Just depends on how you want your setup. I've been using mine this way for 3 years and NO OVERHEATING PROBLEMS.

 

when the vehicle is in overdrive or say above 40 mph, none of the fans run regardless of the AC compressor.
There may be a wire going to the transmission that can indicate or signal when she is in overdrive.

 

on mine i have a switch inline with the a/c compressor wire. when i get on the freeway and i am going to travel i hit the switch. the fans never come on while i am cruising on the freeway and the trauck and a/c stay cool.

 

the latest version of edit has some charts to shut off your fans based on throttle pos and rpm and speed. not sure if you can enable them or not.

 

the flexalite 282's have a 5500cfm rating. they blow some serious air. should be interesting to see what the factory 05 set up looks like.

 

I put the LS1 fans on my truck and just have them controlled by the PCM to turn on and off... Never gets above 195 with the stock 6.0l thermostat...