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.
  • 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. 14.1, Headlight Aiming Screen/Wall

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 small, clear height adjusting dot. Measure the distance from the ground to the center of each height adjusting dot. ( Fig. 14.1 , Item A). Note those distances.
3.
Mark the vertical distances found in step 2 on the screen or wall, directly in front of the headlights. These marks represent the desired locations of each headlight bulb center in the following steps. See Fig. 14.1 , Items 2 and 3.
4.
Turn on the low-beam headlights.
5.
Identify the center of each beam projection by marking the area of brightest intensity on the wall. The area of brightest intensity should fall on or very near the marks made during step 3. See Fig. 14.2 .
  • 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. 14.2, Vertical Low-Beam Headlight Variation Limits
6.
Use Table 14.1 to determine the maximum vertical distance allowable between the marks made in step 3 and the marks made in step 5. If the vertical distance between the marks made in steps 3 and 5 is greater than the maximum distance given in Table 14.1 , 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.
1.
Lift the flap over the rear end of the headlight bucket to expose the two plastic adjusting knobs. See Fig. 14.3 .
NOTE: The right-hand side headlight bucket is shown. The left-hand side is opposite.
  • 1. Horizontal (inboard) Adjusting Knob
  • 2. Vertical (outboard) Adjusting Knob
Fig. 14.3, Headlight Adjusting Knobs
2.
If necessary, adjust the horizontal positioning of the headlights so that each projection points directly forward.
3.
Turn the vertical adjustment knob to adjust the headlight beam to meet the desired height. See Table 14.1 . Turn the knob clockwise to raise the beam; turn the knob counterclockwise to lower it.
4.
Adjust the other headlight.
Vertical Low-Beam Headlight Variation Limits
Distance Between Ground and Headlight: in (mm)
Desired Variation ( Fig. 14.3 , Item 2): in (mm)
Upper Limit ( Fig. 14.3 , Item 1): in (mm) up
Lower Limit ( Fig. 14.3 , 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 14.1, Vertical Low-Beam Headlight Variation Limits