How Should Headlights Be Positioned?

For optimum performance, keep those lights clean, polished and properly aligned.

Headlight adjustment is one of those little maintenance procedures that takes only a few minutes to perform, but can make a huge difference in the driving experience. Headlights can and do go out of adjustment over time, and can prove both an annoyance and a danger to yourself and anyone who has to stare into those lights when you drive by.

Things You'll Need

• Tape measure or yardstick
• Chalk or pencil

Instructions

1. Find a flat, level surface adjacent to a white, vertical wall. Pull the car as close to the wall as possible and lay your yardstick on the centerline of the hood, pointing forward toward the wall. Slide the yardstick forward until it touches the wall, and make sure that it's still sitting perfectly on the car's centerline. Mark the wall with your chalk.

2. Repeat this procedure with the car's headlights, placing the yardstick on top of your hood -- over the top-middle of the headlights -- and marking the lights' horizontal position on the wall. Double-check to make sure that the yardstick is completely square to the wall and the car, and positioned over the center of the headlight bulb. Don't worry about the height yet. Just draw a vertical line along the centerline of the car's headlights.

3. Back the car 25 feet away from the wall; do so very slowly to ensure that you're still square with the wall. Measure the vertical height of the center of your headlights from the ground, then transfer that measurement the the headlight reference marks on the wall. Now, draw a straight, horizontal line between the two headlight reference marks. At this point, you'll have a pair of crosshairs to aim the headlights, and a horizon line for reference.

4. Turn your headlights on the low beam setting. Ideally, they should point directly on the vertical line of the headlight crosshairs, but six inches or so below the horizon line between the crosshairs. Adjustment procedures vary by vehicle, but will usually involve turning a set-screw on the back of the headlight assembly. The side screw controls horizontal movement, and the top or bottom screw controls vertical movement.

5. Finish the adjustment on your low beams. Double-check the setting by engaging the high beams. They should center right on the crosshair horizon line, but just to the right of the vertical headlight centerline. You always want to aim your high beams slightly to the right to avoid blinding oncoming traffic. If your high beams don't center on the horizon line and to the right, then adjust the lights so that they do.

Tips & Warnings

• Alternately, you could adjust the left-side high beam slightly lower than the right side to avoid blinding other drivers. But because that defeats the purpose of having high beams, you may find the right-side bias preferable.

• Always adjust your headlights with a full tank of gas; the extra approximately 200 lbs. sitting behind your rear axle will lever the car's nose upward, potentially throwing off your headlight alignment by several inches.

References

• Popular Mechanics: How to Adjust Your Headlights
• Cool Bulbs: Visual Headlight Aiming Procedure