Headlight Aiming

Preliminary Checks

Before checking or adjusting the headlight aim, complete the following inspection:
Remove any large amounts of mud or ice from the underside of the fenders.
Check the springs for sagging or broken leaves.
Check the suspension for proper functioning of the leveling mechanism. If the vehicle is equipped with an air suspension, make sure that the height is properly adjusted.
With the vehicle unloaded, check that the tires are inflated to the recommended air pressure.
Clean the headlight lenses. Use a soft cloth with mild, non-caustic soap or detergent, and water.

Checking Headlight Aim

1.
Park the vehicle on a level surface, 25 ft (7.6 m) away from, and perpendicular to, a vertical screen or wall. Shut down the engine and set the parking brake. Chock the tires.
2.
Each headlight has a height adjusting dot. See Fig. 19.1 . Measure the distance from the ground to the height adjusting dot on each headlight ( Fig. 19.2 , Item A). Note those distances.
Measure beam height from the ground to the small dot roughly in the center of the headlight lens.
Fig. 19.1, Headlight Beam Height Adjusting Dot
  • A. Measure the distance from the ground to the center of each headlight bulb.
  • B. Mark where the center of each headlight projection should appear.
  • 1. Screen or Wall
  • 2. Center of Right-Hand Headlight Projection
  • 3. Center of Left-Hand Headlight Projection
Fig. 19.2, Headlight Aiming Screen/Wall
3.
On the screen or wall, mark the locations of each headlight bulb center using the distances found in step 2. See Fig. 19.2 , Items 2 and 3.
4.
Turn on the low-beam headlights.
5.
Check the vertical adjustment of the low beams. The center of each beam projection should fall on or near the marks made during step 3. See Fig. 19.3 .
  • A. Park the vehicle on a level surface 25 ft (7.6 m) away from a vertical screen or wall
  • 1. Low-Beam Angle Upper Limit
  • 2. Ideal Low-Beam Projection
  • 3. Low-Beam Angle Lower Limit
Fig. 19.3, Vertical Low-Beam Headlight Variation Limits
6.
Use Table 19.1 to determine the maximum vertical distance allowable between the marks on the wall and the center of each low-beam projection.
6.
If the distance between either projection center and the mark made on the wall or screen is greater than the maximum distance given in Table 19.1 , adjust the vertical positioning of that headlight.

Adjusting Headlight Aim

NOTE: Freightliner vehicles are offered with various headlight assembly options. Because of the various options, the location of adjustment screws on your vehicle's headlight assembly may vary from what is shown here.
The adjusting screw is located on the upper outboard corner of the headlight assembly. See Fig. 19.4 . Turn the adjusting screw clockwise to raise the beam and counterclockwise to lower it, until the beam pattern meets the acceptable standard.
  • 1. Headlight Adjusting Screw
Fig. 19.4, Headlight Adjusting
Vertical Low-Beam Headlight Variation Limits
Distance Between Ground and Headlight: in (mm)
Desired Variation ( Fig. 19.3 , Item 2): in (mm)
Upper Limit ( Fig. 19.3 , Item 1): in (mm) up
Lower Limit ( Fig. 19.3 , Item 3): in (mm) down
22–36 (560–900)
0
3.9 (100)
3.9 (100)
36–48 (900–1200)
2 (50) down
2 (50)
6 (150)
48–54 (1200–1400)
2.5 (64) down
1.6 (40)
6.5 (165)
Table 19.1, Vertical Low-Beam Headlight Variation Limits