[ford38v8]

Not to disagree with Tubman's reply, mine says the same thing with different wording:
With solenoids fed by 10 gauge wire, one each for high beam and low beam, mounted up front near the radiator, you'll get full battery voltage as close as practical to the headlights. Those solenoids being triggered by the original circuits which run through smaller gauge wire, headlight switch, and dimmer switch, will have too much built-in resistance for the headlights, but sufficient voltage to activate the solenoids.