GM Service Manual Online
For 1990-2009 cars only

Visual Aiming Procedure

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Object Number: 471801  Size: SH
  • All equipment for testing headlamps must comply with the SAE Recommended Practice for Headlamp Inspection Equipment.
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  • If you use a headlamp testing machine, the machine should give results equivalent to the results obtained using the screen procedure.
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  • The machine should be in good condition and be properly adjusted.
  • Use the machine in accordance with the manufacturer's instructions.

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  • Machines that use a photoelectric cell or cells to determine aim, should also include a visual screen on which you can project a beam pattern proportional to the beam appearance, and aim on a screen at 10 m (32.8 ft).
  •    - The screen should be plainly visible to the technician who is adjusting the headlamps.
       - The screen should have horizontal (3) and vertical (1,2) reference lines in order to permit visual evaluation of the headlamp beam.

    Headlamp Aiming Location (Using Screen Method)

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    Object Number: 471799  Size: SH
  • The aiming area should be darkened and large enough to allow for the vehicle and an additional 10 m (32.8 ft), measured from the face of the headlamps (2) to the front of the screen (1).
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  • The floor on which the vehicle rests must be parallel with the bottom of the screen.
  • If the floor is not level, compensate accordingly.

    Headlamp Aiming Screen

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    Object Number: 471801  Size: SH
  • If you use a screen, the screen should be at least 1.52 m (5 ft) high x 3.66 m (12 ft) wide with a matte white finish, well shaded from extraneous light.
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  • Properly adjust the screen to the floor on which the vehicle rests.
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  • The screen should be moveable so that you can align the screen parallel to the rear axle of the vehicle.
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  • Position the screen so that a horizontal line (3) drawn perpendicular to the centerline of the screen will pass an equal distance midway between the two headlamps.
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  • The screen should have the following items:
  •    - A vertical centerline
       - Two laterally adjustable vertical tapes (1,2)
       - One vertically adjustable horizontal tape
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  • If a regular commercial aiming screen is not available, the screen may consist of a wall having a clear, uninterrupted area at least 1.83 m (6 ft) x 3.66 m (12 ft) wide. The surface should be finished with a no-gloss white paint.
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  • After the aiming screen has been set up and located, paint or tape a reference line on the floor 7.62 m (25 ft) from the screen. Park the vehicle with the front of the headlamps directly over this reference line.
  • Headlamp Aiming Procedure

    1. Park the vehicle square with the screen, with the headlamps directly over this reference line.
    2. Ensure that the components are in place if other work has been done on the vehicle.
    3. Ensure that the vehicle is on a level surface.
    4. Stop all other work on the vehicle.
    5. Ensure that the vehicle has half a tank, or less, of fuel.
    6. Close all of the doors.
    7. Rock the vehicle sideways.
    8. Line up the centerline of the vehicle with the centerline of the aiming screen.
    9. • Mark the vertical center of the rear and front windows using tape.
      • Use these lines as sights in order to line up the centerline of the vehicle and the screen.
    10. Adjust the vertical tapes on the screen in order to match the vertical centerline of each low beam headlamp.
    11. Measure the distance from the centerline of the low beam lamp.

    12. Adjust the horizontal tapes on the screen in order to match the horizontal centerline of each low beam headlamp.
    13. Measure the height from the floor to the center of the low beam.

    14. Turn on the low beam headlamps.
    15. Observe the left and the top edges of the high intensity zone on the screen.
    16. Adjust the headlamps to the following specifications:
    17. • The top edge of the center of intensity on the screen for the low beam should be less than 101.6 mm (4 in) above or below the cross section of the headlamp centerlines.
      • The left edge of the center of intensity on the screen for the low beam should be less than 101.6 mm (4 in) to the left or right of the cross section of the headlamp centerlines.

      Object Number: 473531  Size: SH
    18. In order to adjust the horizontal aim, insert the screwdriver (2) and turn the horizontal headlamp adjusting screw.
    19. In order to adjust the vertical aim, insert the screwdriver (1) and turn the vertical headlamp adjusting screw.

    Alternative Headlamp Aiming Procedure

    Tools Required

    J 25300-D Headlamp Aiming Kit

    Properly aim the headlamps in order to obtain the maximum road illumination and safety of the headlamp system. Always aim the headlamps if removing the headlamp assembly from the vehicle. Composite headlamps do not require aiming if replacing only the bulb.

    When inspecting or adjusting the headlamp aim, observe the following conditions:

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  • Ensure the vehicle is on a level surface.
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  • Inflate all of the tires to the specified pressure.
  • Refer to the tire placard for tire pressure specifications. Refer to Tire Placard in General Information for the location of the tire placard.

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  • Inspect vehicles that tow a trailer or carry an unusual load under the same conditions.
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  • Clean the headlamps before aiming.
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  • Follow the state requirements for headlamp aiming.
  • The J 25300-D is designed to accommodate all composite and sealed beam headlamps in any standard shape or size and in any configuration. Use the adapters provided in kits for different lamp shapes and sizes. Regardless of the configuration, aim the headlamps in pairs.

    Use the following list in addition to the mounting and adjustment instructions included in the J 25300-D in order to aim the headlamps


      Object Number: 233619  Size: MH
    1. Use the universal aimer on a level floor, or calibrate the aimer for the floor slope.
    2. Select and assemble the universal adapter which matches the aiming pad pattern on the lens of the headlamp.
    3. Align the selected adapter to the aiming pads.
    4. Move the adjustment rod for each pad until correlated with the adjustment rod setting numbers located on the headlamp.

      On some headlamps, the numbers are located on the lower edge of the vertical edge of the lens.

    5. In order to adjust the rods (2) to the required positions, turn the rods (2) to the neutral position (4).
    6. Slide the rods in or out to the proper setting.


      Object Number: 233616  Size: MH
    7. Verify that the correct adapter is issued using the correct side aimer.
    8. Attach the adapters. Using the adapters, place the aimer onto the respective sides.
    9. Ensure the all adjustment rods (6) and the articulating suction cups (4) are contacting the aiming pads (1,3).
    10. Add or remove extension studs as needed.
    11. Aim the headlamps according to the instructions included with the J 25300-D .

    12. Object Number: 473531  Size: SH
    13. In order to adjust the horizontal aim, insert the screwdriver (2) and turn the horizontal headlamp adjusting screw.
    14. In order to adjust the vertical aim, insert the screwdriver (1) and turn the vertical headlamp adjusting screw.