As 69Cuda says, the outside head lights have dual filaments. When on low beam 1 filament lights, when high beam is switched on that filament goes out, and the other (high beam) filament comes on. Just maybe the (high beam) filaments are burned out on both the outside head lights. Did you check to see if you had voltage with a test light or meter at the green and brown wire terminals on the back outside head lights when in the high beam position?
