I found this on another website. Hope it is helpful:

http://mymonte.com/home/content/view/256/26/

High beam with Low beam conversion.
This is how you can go about making your car have the low beams activate when you have high beams on.

Parts needed:
-30Amp Relay
-4 Wire clips to attach to relay
-2 Inline wire taps
-about 10' spool of wire between 16-12 gauge
-inline fuse holder with 20 amp fuse
-2 loop conectors

Basic Setup:
-Locate power that goes to High beam. Use this as the source/ triger for the relay. Use inline tap.
-Run power from battery, with inline fuse inplace, to the relay.
-Run ground for relay.
-Run Power from relay to the Positive wire on the Low beams.
Once all is hooked up, you are done! turn on your high beams and check the system.

***If you want to link your fog lamps and your high beam/low beams this is what you will need. Two relays and the same items for each install.

First relay: the trigger for the relay is comming from a pos interior light source (one that is on only when lights are on, like your interior instruments) on a switch. This relay is powering the fog lamps and a second relay for the Hi/Low conversion.

Second relay: The trigger is the high beams and the power input Power is coming from the first relay. The output for this second relay goes to the low beams. This way you can shut of the switch and turn off the low beams and fog lamps if you got the high beams and if you just have your low beams on you would be able to toggle your fogs.

 

Sounds like a cool mod... Are you going to try it??

 

The '06 already comes from the factory with high and low setup. But I want to try to get the fogs to stay on with the high and lows altogether.

 

I did this on my Silverado. One of my favourite mods. Made a big difference in nighttime visibility.