• 2019

Lighting it Up

A QUICK GUIDE TO ADJUSTING HEADLAMPS AND FOG LAMPS

Headlamp aiming rarely needs to be done. However, if there is damage tot he headlamp assembly or an accident, headlamp aiming might be required. The method for aiming headlamps involves projecting the light pattern onto a vertical screen or wall. The position of the light pattern is then adjusted vertically to the correct spot by rotating an adjustment screw.

VEHICLE PREPARATION

To correctly aim the headlamp beam, the vehicle must be properly prepared. Check the headlamp bulb operation and replace any that may be burnt out. Next, repair and/or replace any worn or damaged body and/or suspension components that could hinder proper headlamp alignment.

Note: If the vehicle is equipped with an automatic load leveling suspension, drive it for approximately three miles before attempting this procedure; if the vehicle is equipped with a manual headlamp leveling, set the leveling switch to the 0 position. Be sure that all four tires are properly inflated, then verify that there is no load in the vehicle (cargo or passengers) other than the driver. The fuel tank should be full and, if it’s not, add 6½ pounds of weight over the fuel tank for every gallon of missing fuel. Then, verify that the vehicle suspension height is correct. Finally, lean the front headlamp lenses.

FRONT LAMP ALIGNMENT SCREEN

Figure 1

Proper headlamp aiming can only be accomplished when the headlamp pattern is projected onto a suitable alignment screen. In most cases, this screen is simply a wall in a garage or service bay. Vertical and horizontal lines are drawn on this screen to show the location of the projected light beams. Refer to Figure 1, which illustrates a typical front lamp alignment screen.

Note: Select a location with a level floor that is perpendicular to the particular wall being used as the screen.

Tape a line on the floor (1) parallel to and 25 feet from the screen. The floor will be used as the horizontal zero reference. Tape a second line on the floor (2) perpendicular to both the alignment screen and first tape line. This tape line must be outboard of either side of an imaginary line representing the side of the vehicle. This line will be used as the vertical zero reference.

Position the vehicle as described above 25 feet from the screen, with its side parallel to the vertical zero reference. Also, the front headlamp lenses must be in the vertical plane of the horizontal zero reference (the tape line (1) that is parallel to alignment screen).

Rock the vehicle side-to-side three times to allow the suspension to stabilize. Jounce the front suspension three times by pushing downward on the front bumper and releasing it.

Measure the distance (3) between the optical center of the headlamps being aimed and the floor. Transfer this measurement to the alignment screen with a piece of tape placed parallel (horizontal) to the floor. This line will be used as the lamp horizontal reference.

Next, measure the distance (4) between the vertical zero reference and the optical center of the nearest headlamp being aimed. Transfer the measurement to the alignment screen with a piece of tape placed vertically across the lamp for horizontal reference. This is the centerline reference (5) for the first headlamp. Repeat this step for the second headlamp being aimed and transfer that measurement with tape. This is the centerline reference (6) for the second headlamp.

 

HEADLAMP ALIGNMENT

A properly aimed low beam headlamp will project the top edge of the high-intensity pattern (cut-off) on the alignment screen from the horizontal line (lamp horizontal reference) to a spot 2.1 inches below this horizontal line. No horizontal (right/left) adjustment required. The high beam pattern should be correct when the low beams are aligned properly. Vehicles that are equipped with High Intensity Discharge (HID), such as the Dodge Charger, require a slightly modified alignment screen for adjusting the front headlamps. Refer to the Charger service manual for details.

 

Turn the headlamps ON and select the LOW beam. Using a screwdriver, rotate the headlamp adjustment screw on each front lamp to adjust the beam height as required. Each vehicle has its own adjustment screw location and design. Some vehicles, such as the 2014 Dodge Journey (see Figure 2), have a horizontal adjustment screw. To access it, you must reach inside the engine compartment to locate the screw and rotate it horizontally.

Figure 3 shows the adjustment screw for a typical minivan. Note that the screw is located between air cleaner box and the front of the vehicle. This is the vertical design for a headlamp adjustment screw. This is the most common design.

For the location of the headlamp adjustment screws for the vehicle being serviced, refer to the appropriate service manual.

FOG LAMP ALIGNMENT

The same front lamp alignment screen used for headlamps can also be used to aim the fog lamps. The horizontal zero reference and the vertical zero reference are the same for both types of lamps. The difference, though, is in determining the centerline reference.

Instead of measuring from the optical center of the headlamp for these measurements, simply measure from the optical center of the fog lamp. The result will be centerline references on the  alignment screen that are below the ones made for the headlamps. The horizontal locations of these references might be different, too, as the fog lamps probably are not directly below the headlamps.

Turn the fog lamps ON. On many vehicles, such as minivans, you can use a screwdriver inserted through the access in the underside of the front fascia below the fog lamp to rotate the vertical adjustment screw and adjust the beam height, as required. Refer to the appropriate service manual for the adjustment procedures for the vehicle being serviced.

A properly aimed front fog lamp will project a light pattern on the alignment screen that is approximately 4 inches below the fog lamp centerline reference and straight ahead of the lamp.