How many headlights do I have?
Vehicles are manufactured with two different types of systems, either the Four Headlamp System or the Two Headlamp System. With a Four Headlamp System, different bulbs are used for the high beam setting and for the low beam setting. You will find four different sealed beam housings or four different capsules in your front headlight area. With the Two Headlamp System, the same bulb is used for both the high and low beam settings. There will be one sealed beam or capsule on either side of the forward lighting area.
How often should headlamps be checked?
Headlights typically burnt out or they fail due to debris and rocks, minor fender benders, ice and snow damage, can shatter or crack a headlamp lens leaving it useless. Sometimes it's not easy to notice a burnt out headlamp from behind the gunk, so it's a good point to checking them regularly during gas station stops when you squeegee the headlamp lenses as well as the windshield.
What should be replaced?
Headlamps in today's cars are built with either a sealed beam headlamp or a replacement capsule system.
With a sealed beam, the bulb is permanently mounted inside a glass housing, which mounts to the car's metal frame. When this type of headlamp burns out, you need to replace the entire unit. The capsule has a removable bulb and base housing installed into a glass or plastic lens housing, which is permanently attached to the vehicle.
Do-it-yourselfers can buy the correct pair of sealed beams or capsules at the local auto parts store, and follow the easy-to-install instructions on the package. Your vehicle maintenance manual may provide additional assistance.
Timing of lamps replacement<BR> Always replace in pairs! Whether its both low beam or high beam headlamps or the dual beam lights, replace each like system in pairs. Parts tend to wear out (or break) at or around the same time, based on their design and manufacturing.