Shouldnt there be a wire connecting to the relay plug that controls high for that particular fan? Why couldnt i splice those wires and run them to a 3 prong switch with hot and ground? I want to use an on-off switch with three prongs on the back. Is that possible?

 

yea if you use diodes

 

Also since this is a nelson harness, Atomic would your wiring diagram work since the A/c relay is triggered off of a positive signal not a ground.

 

Im not sure if that version connects to the pcm or not, or just the ac wire, but this should work

 

So which relays and wires control the high stage on the fans

 

Yeah. I was thinking of the two pin harness at first and forgot that the A/c relay triggers positive. That new one should work.

To control High on both fans both relays have to be triggered.

 

when its flipped up, the fans are on low, when its flipped down they come on high.

an issue with this would be you can still turn the fans on low with the engine off, by grounding the green wire. I have mine wired this was so i can run my fans to cool off my engine bay with the engine off, but to be safe to make sure you dont accidently run down your battery, you can put a relay on the green wire to only close when there is accessory power.

 

when its flipped up, the fans are on low, when its flipped down they come on high.

an issue with this would be you can still turn the fans on low with the engine off, by grounding the green wire. I have mine wired this was so i can run my fans to cool off my engine bay with the engine off, but to be safe to make sure you dont accidently run down your battery, you can put a relay on the green wire to only close when there is accessory power.