1, Types of Headlight bulbThe headlight bulb includes high beam, low beam, fog light and turn light, while there are many models for headlight bulb, mainly divided into H category and D category, and we could distinguish them based on headlight base and latch quantity. Common models are H1、H3、H4、H7、H11...etc. , headlight bulb of different model is used for different position.Model H1: the headlight bulb is widely used for trucks, a frequently used model, which is distinguished very easily, slender light body and base, tail has a socket pin only, the negative pole is connected at headlight base, the interior has a filament only, usually used in high beam headlight bulbs place, a few for fog headlight bulb.Model H3: the headlight bulb is tiny and small, unlike other models, it has no wiring pins, just a long connecting wire and an internal filament, which is often used in front fog headlight bulbs as well as as a headlight source.Model H4 : the larger one in headlight bulbs, looks strong, it is characterized by three socket pins and two internal filaments, a bulb can complete the conversion of high beam and low beam light sources, and it is a very wide application in headlight bulb model.Model H7: slightly smaller than H4, with two socket pins and an internal filament, generally used in the low beam part.Model H8/H9/H11: These three models are L-shaped bulbs with single filament and two socket pins. They are widely used and have small headlight body design, which are one of the mainstream models of led headlight bulbs. However, base and appearance of H8 / H9 /H11 are basically the same, their difference is the power, so they are used at different positions. H8 is 35W, usually used in fog headlight bulbs. H9 is 55W, generally used in high beam. H11 is 55W, generally used in low beam.Model 9005, 9006 (HB3): 9005 and 9006 (HB3) are L-shaped bulbs with single filament and two socket pins. The difference is that 9005 is generally used in high beam, while 9006 is used in low beam.2, How to choose appropriate headlightFirst of all, you need to check if the car has a lens, whether high beam and low beam is separated, whether the installation position is enough or not, whether decoding is required or not, and so on.A. With lens or not:strictly speaking, headlight bulbs used by cars with lenses are different from headlight bulbs used by cars without lenses. The main difference lies in the design of headlight bead between headlight bulbs specially designed for lens and ordinary headlight bulbs . headlight bulbs specially designed for lens mostly use cross light bead, which can eliminate the dark area of headlight bulb lighting.B. Separating High beam and low beam or not: headlight bulbsare different between cars separating high beam & low beam and those integrating high beam&low beam, with different light bead design. For those separating high beam and low beam,low beam normally use strip light bead, while high beam generally use square light bead; those integrating high beam and low beam generally use cross lamp bead. Bead design difference is for light type, not blinding.C. Headlightbulb installation position is enough or not: some cars have very short position for headlight installation, for instance Highlander, high beam for novel X-Trail, require installing tailored short headlight, and common headlight couldn’t be installed.D. Decoding or not: VW, Skoda, Jeep require decoding, which need to fit headlight bulbswith decoding function.Secondly, it is necessary to choose the appropriate color temperature. Different types of headlight bulbs have different requirements for color temperature. For example, the color of light for headlight bulbs can be white, yellow&white or yellow, but fog headlight bulbs must be yellow. White light has a color temperature of 6000K or 6500K, yellow light has a color temperature of 2500K or 3000K, and yellow & white light has a color temperature of 4300K.3. How to install headlight bulbs(1) Determine the type of headlight bulb you needDifferent car models and positions correspond to different headlight bulbs. Generally, the user manual of a car will have relevant information. If there is no manual, you can also search online to find the corresponding headlight according to the car model. You can also take the damaged headlight bulb to the store and find a new headlight bulb of the same model.(2) Remove the bulbOnce parked, prepare a pair of latex gloves, flashlight, flat-head screwdriver, some sleeves, and a pair of needle-nosed pliers. We need to open the engine cover to find the position of the headlight to adjust the bolt. Different vehicle model has different headlight design, so the bolt position also differs, but the bolt is in the rear of the headlight assembly for most vehicle models, which is not difficult to find around here. The adjustment bolt for most models is with teeth around, very easy to judge, the center is hexagon or hexagon + Phillips screwdriver groove, and some models are hexagonal nuts. It should be noted that some headlight bulbs are integrated high beam & low beam, so there are generally two adjusting bolts to adjust the height and width; while headlight bulbs with independent low beam&high beam can adjust the height of the low beam and high beam respectively, but also can adjust the width at the same time, so there may be 3-4 adjusting bolts. Therefore, when we adjust, don't unscrew all the bolts at once. Fine-tune first to see what each bolt is responsible for, and then adjust the bolts that require adjusting.(3) Adjust the positionBeam irradiation angle and focus distance need to be adjusted for headlight bulbs of some cars, but it is difficult to adjust the position of headlight bulbs by ourselves, which can not be adjusted according to the standard data, how to judge?A, People as a ruler: first of all, we can use people as a ruler, for example, a people about 1.8 meters tall stands 2-3 meters from the front of the car, it will be appropriate that the light is in the middle position of the thigh, if the light is at the waist, that is too high. Of course, everyone has different height and leg-to-body ratio, so this can only be a rough guideline.B, The vehicle in front as a ruler: we can observe the situation of our headlight bulbs shine the vehicle in front of us when driving. Let the vehicle in the rear of a car, observe the position of the tangent line for the low beam, to ensure that the headlight will not shine on the rear windshield of the car in front at any distance, otherwise it will affect the driving safety of the car in front at night, and will also let the car in front misunderstand that you’re flashing the high beam, which is annoying. No need to pay too much attention to the lower limit position of the low beam, and it shall prevail that being able to see clearly the road ahead of about 20 meters .4. Some notes on the new headlight bulbChoose a clean driveway or work area (such as a garage) with plenty of light. Be patient and allow yourself enough time (at least two hours) to replace your headlight bulbs. It can be simple, but it can also be more complicated than you expect. Place removed clips and fasteners in jars or other containers. Otherwise they are easy to lose. Use tape and a marker to mark the location of the wiring so that it can be reconnected in the same way to make sure the connection is correct. Lay a carpet, rubber mat or clean cardboard on the floor to make it easy for you to kneel or work under the car. You should hear, or feel, a clicking sound as you connect the joint to indicate the good connection. When replacing headlight bulbs, it is vital to avoid touching the glass of the new bulb, as even the smallest amount of dirt from the skin can shorten the life of the bulb. A little dielectric sealing grease can be applied to the bulb plugs and terminals (if new bulbs don't come with them, buy them at an auto parts store) to prevent rain erosion. Also, do not confuse headlight bulb adjustment screws with other similar set screws.