Another potential problem with dim or inoperative headlights is the dimmer switch. It's down there in a very wet, dirty, salty, and generally hostile environment. I like to use the headlight switch and dimmer to carry very low amperage to switch relays on and off for the main headlight current. That setup makes regular lights noticeably brighter, and it's just about a necessity when an upgrade to halogen or high output LED headlights is done.
Jerry
