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westrope65, ASE Certified Technician
Category: Car
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Experience:  ASE
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how do you change the headlight on a 1991 ford f150

Customer Question

No Comment Added
Submitted: 9 years ago.
Category: Car
Expert:  Eric replied 9 years ago.


Are you trying to change the headlight bulb or the whole headlight?

Customer: replied 9 years ago.
Reply to Eric's Post: headlight bulb
Expert:  westrope65 replied 9 years ago.

Hi, welcome to

Here is instructions to change the headlight assembly. Some times you can not get your hands in to do just the bulbs. If you can dont remove the assembly just use portion that is for headlight bulb. This is the basic procedure so some pictures maybe different.


See Figures 1, 2 and 3

Click image to see an enlarged view
Fig. 1: Headlamp components


Click image to see an enlarged view
Fig. 2: Twist it counterclockwise


Click image to see an enlarged view
Fig. 3: DO NOT touch the headlight bulb glass-if you do, wipe it clean with an alcohol soaked paper towel


The headlamp bulb contains high pressure halogen gas. The bulb may shatter if scratched or dropped! Hold the bulb by its plastic base only. If you touch the glass portion with your fingers, or if any dirt or oily deposits are found on the glass, it must be wiped clean with an alcohol soaked paper towel. Even the oil from your skin will cause the bulb to burn out prematurely due to hot-spotting.

  • Make sure that the headlight switch is OFF.

  • Raise the hood and find the bulb base protruding from the back of the headlamp assembly

  • Disconnect the wiring by grasping the connector and snapping it rearward firmly.

  • Rotate the bulb retaining ring counterclockwise (rear view) about 1/8 turn and slide it off the bulb base. Don't lose it; it's re-usable.

  • Carefully pull the bulb straight out of the headlamp assembly. Don't rotate it during removal.


    Don't remove the old bulb until you are ready to immediately replace it! Leaving the headlamp assembly open, without a bulb, will allow foreign matter such as water, dirt, leaves, oil, etc. to enter the housing. This type of contamination will cut down on the amount and direction of light emitted, and eventually cause premature blow-out of the bulb.

    To install:

    1. With the flat side of the bulb base facing upward, insert it into the headlamp assembly. You may have to turn the bulb slightly to align the locating tabs. Once aligned, push the bulb firmly into place until the bulb base contacts the mounting flange in the socket.

    2. Place the retaining ring over the bulb base, against the mounting flange and rotate it clockwise to lock it. It should lock against a definite stop when fully engaged.

    3. Snap the electrical connector into place. A definite snap will be felt.

    4. Turn the headlights on and check that everything works properly.



    See Figure 4

    Click image to see an enlarged view
    Fig. 4: Headlamp adjustment points


    The headlights must be properly aimed to provide the best, XXXXX XXXXX illumination. The lights should be checked for proper aim and adjusted as necessary. Certain state and local authorities have requirements for headlight aiming; these should be checked before adjustment is made.

    Each headlight is adjusted by means of 2 screws located at the 10 o'clock and 3 o'clock positions on the headlight underneath the trim ring. Always bring each beam into final position by turning the adjusting screws clockwise so that the headlight will be held against the tension springs when the operation is completed.

    Headlight adjustment may be temporarily made using a wall, as described below, or on the rear of another vehicle. When adjusted, the lights should not glare in oncoming car or truck windshields, nor should they illuminate the passenger's compartment of vehicles driving in front of you. These adjustments are rough and should always be fine-tuned by a repair shop which is equipped with headlight aiming tools. Improper adjustments may be both dangerous and illegal.

    Before making any headlight adjustments, perform the following preparatory steps:

    1. Make sure all tires are properly inflated.

    2. Take into consideration any faulty wheel alignment or improper rear axle tracking.

    3. Make sure there is no load in the truck other than the driver.

    4. The truck's fuel tank should be about half full.

    5. Make sure all lenses are clean.

    To adjust:

    1. Park the truck on a level surface, with the fuel tank no more than 1/2 full and with the vehicle empty of all extra cargo (unless normally carried). The vehicle should be facing a wall which is no less than 6 feet (1.8m) high and 12 feet (3.7m) wide. The front of the vehicle should be about 25 feet (7.6m) from the wall.

    2. If this is be performed outdoors, it is advisable to wait until dusk in order to properly see the headlight beams on the wall. If done in a garage, darken the area around the wall as much as possible by closing shades or hanging cloth over the windows.

    3. Turn the headlights ON and mark the wall at the center of each light's low beam, then switch on the "brights'' and mark the center of each light's high beam. A short length of masking tape which is visible from the front of the truck may be used. Although marking all 4 positions is advisable, marking 1 position from each light should be sufficient.

    4. If neither beam on one side of the vehicle is working, park another like-sized truck in the exact spot where the truck was and mark the beams using the same side light on that truck. Then switch the trucks so the truck being worked on is back in the original spot. The truck must be parked no closer to or farther away from the wall than the second vehicle.

    5. Perform the necessary repairs, but make sure the truck is not moved or is returned to the exact spot from which the lights were marked. Turn the headlights ON and adjust the beams to match the marks on the wall.

    6. Have the headlight adjustment checked as soon as possible by a reputable repair shop.

    hope this helps.______________

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