Checking and Changing a Headlight Bulb

There are many types of headlight bulbs available. Always make sure you replace a bulb with one of exactly the same type. Sealed-beam units require that the whole light be replaced when one filament has failed. If the reflector in the sealed-beam light shows signs of degradation, it also indicates that you must change the unit. If both lights operate but are not bright when switched on, start the engine to see if this solves the problem; the battery may be in a poor state of charge. When replacing a halogen bulb, avoid touching it with your fingers, which can leave a residue from your fingers on the outer surface. This residue can cause the bulb to crack or shatter and burn out after a short time of operation. If you inadvertently touch the bulb, clean it with alcohol and a lint-free cloth. Do not use gasoline or paraffin to clean the bulb.

To check and change a headlight bulb, follow the steps in Skill Drill 39-3:

1
Assessing headlight operation is always more accurately carried out in a dim environment. Switch the vehicle headlights on at low beam, then switch to high beam. Check that the high beam indicator on the instrument panel is operating. Note the change in the intensity of the lights. If one of the lights does not operate, that headlight will need to be diagnosed and potentially replaced.
2
Determine the type of lamp installed on the vehicle and obtain a replacement. Many vehicles today are equipped with halogen headlights. These are twice as powerful as older sealed-beam units and need to be handled carefully. Always follow the manufacturer’s handling instructions.
3
Unplug the electrical connector at the back of the lamp unit. On most vehicles, it is not necessary to remove the lamp unit from the vehicle. If equipped, unscrew the bulb-retaining ring or twist the bulb from its housing. (Photo 1)
4
Remove the old bulb and replace it with the new one. Handle the new bulb only by its base or, if supplied, by the card cover. It is very important that you never touch the surface of the bulb with your fingers, as this will cause it to burn out very quickly. (Photo 2)
5
Replace the unit and the retaining ring or bulb assembly, and then plug in the connector. Switch on the lights again to confirm that they are both operating correctly. (Photo 3)
SKILL DRILL
39-3
Checking and Changing a Headlight Bulb
24118 CH32 SKDSD09 05
1
Test the vehicle headlights. Obtain the replacement lamp for the vehicle. Unplug the electrical connector at the back of the lamp unit.
24118 CH32 SKDSD09 05
2
Remove the old bulb and replace it with the new one. Handle the new bulb only by its base or, if supplied, by the card cover.
24118 CH32 SKDSD09 05
3
Replace the unit and the retaining ring or bulb assembly, and then plug in the connector. Switch on the lights again to confirm that they are both operating correctly.
 
Technician Tip
A customer with sealed-beam headlights once complained of poor headlight performance. When the technician turned on the lights, they both worked but didn’t seem to create much light. As the technician opened the hood to investigate further, he noticed something strange. The headlights were shining light out the back of the lights, illuminating the engine compartment. He inspected the lights and found that the metallic reflector in the sealed beams had pretty much all flaked away, allowing most of the light to exit the rear of the bulb, instead of being reflected forward. Replacing the sealed-beam headlights with new ones fixed the customer’s concern.