OK .. I don't know if this has been answered or not .. but here's my answer for what it's worth.

The fuse box under the hood, remove the brace over it with a 13mm socket. Take the cover off, flip the fuse block up. In the middle section (from left to right) there are (on mine anyways) 3 green wires, one solid and 2 with a white stripe. The solid green wire was the AC clutch positive lockup wire. This wire was about half way down from top to bottom. For the ignition switched wire, I used a pink wire on the right side, close to the top.

You can get a volt meter or a test light out to make sure you have the right wires.

On a side note .. if you touch the AC clutch wire to positive while the truck is off, you will hear the clutch lockup AND the fuel pump turn on for the 3 seconds before the engine starts.

You might also look for a different ignition wire, I think the one I used gave me some noise in my aftermarket radio. Not sure on that one yet.

Hit Man .. I have a theory about the fans drawing power at highway speeds. When sitting still, they are having to work hard at keeping their speed, using lots of amps. When at highway driving, wouldn't the air forced from the speed 'help' the electric motors out and take a lot of the strain off of them therefore not requiring near as much power?

BTW .. I have the Flex-A-Lite fans.