interesting thought.. i'd like to know too.. although i run w/ the headlights and fogs on all the time for better visibility to other drivers(especially with the silverstars :rck: ), and to be intimidating when i come up behind them lol
i'm thinking there's probably a computer in there somewhere, plus the sensor on the dash
There are ways to make auto headlights. You have 2 options. Do you want them to come on all the time that your truck is running? Or would you like them to come on when it's dark out?
If you want them to be on all the time your engine is running that is very simple. All you would have to do is re-wire the switch so that the power out put of the switch is getting power with the key in the run position. You could also by-pass the switch. You should use a relay or find an unused fused wire that can handle up to 30 amps. That way you don't melt anything.
If you want your lights to come on only when it's dark out you would have to buy a sensor.
Those are the easiest ways that I know of.