On my 1990 Ford Crown Victoria, the left headlight went out recently, but when I turn on the hi-beams, all 4 lights come on. What gives? This happened on my '86 Caprice, too. Thanks.
The low beam headlights in your crown vic are dual elements. Meaning they have both a low beam element and a high beam element that are powered through different wires (thus the reason for three prongs and wires). The low beam element is burned out but the high beam element is still intact.
Thanks, Michael. I knew it was something simple.