1, Level your car.
Start by removing any excess weight from the trunk of the car. Also, ensure that the tire pressure in all tires is at the manufacturer's recommended levels. If possible, have somebody sit in the driver's seat, and that the gas tank is half-full. As well as this, check that your headlight aim adjustment wheel (if fitted) is at the zero position.
2, Position your car.
On level ground, park 10 to 15 feet (3.0 to 4.6 m) from a dark wall or garage door, with the front of the car aimed at the wall. A paved parking lot or level driveway is best.
- Bounce the car a couple times on all four corners to make sure the shocks are leveled.
- Measure the distance to the ground from both headlights to ensure that the suspension itself is level.
Do not use your high beams or fog lights. Mark the horizontal and vertical center lines of the headlight beams with masking tape to make two T’s on the wall or garage door.
Place a carpenter’s level between the two marked center lines to see if they are even. If they are not even, use a tape measure to measure how far up the wall the lower mark is and lower the other center line marker to the same height. These center lines should be no higher than 3.5 feet (1.1 m) from the ground.
Don't estimate the distance! Use a tape measure to make sure you are the proper distance away from the wall. Turn off the headlights. Remove the trim ring from around the headlights and locate the adjusting screws. These screws are typically found adjacent to the headlight, though some manufacturers put the screws in the engine compartment, behind the the headlights. The horizontal adjuster and the vertical adjuster should be marked.
- Always defer to the specs in the owner's manual—some manufacturers recommend different distances for proper adjustment. For example, Toyota recommends 10 feet (3.0 m) feet, Pontiac GTO recommends 15 feet (4.6 m), and Chrysler recommends 3 feet (0.9 m) for some models. For this reason, it's important to check your owner's manual and follow those guidelines.
- There should be one screw at the top of the headlight to adjust vertically and another screw to one side of the headlight to adjust horizontally, though some cars may feature adjustment bolts rather than screws.
- Turn the headlights on after adjusting and look at the light pattern on the wall. The top of the most intense part of the beam should be even with, or just below the center of the line of tape you made.