Illuminated by oil or acetylene gas, the first headlights made their debut in the late 1880s. Acetylene lamps produced a flame that was resistant to the windy, rainy and snowy conditions common during Michigan winters. After experimenting with various reflectors, Corning was able to produce a lamp that could illuminate a sign 500 yards away. Although electric lights became available during the next decade, they were not popular because of their inconsistent performance and low power.
This changed after the turn of the 20th century. Several car manufacturers added headlights as standard equipment when electrical systems improved. The modern sealed beam headlight was introduced in 1940. For nearly two decades, the federal government mandated that automakers use the round seven-inch headlight, which stifled innovation. When this requirement was lifted in 1957, manufacturers in the U.S., Germany and Japan were able to develop newer, more advanced technologies, such as halogen and LED bulbs. Automakers also offered stylish headlight assemblies in various shapes and sizes that served as the forerunners of those currently used on the Camry, Tundra and RAV4.
Despite the advancements, headlights will still fail for a variety of reasons. Because they are mounted on the front of a car, truck or SUV, headlights are exposed to flying road debris as well as the harsh effects of Michigan’s weather. Headlights are an essential safety feature that enables you to operate your vehicle during periods of low visibility. When a headlight malfunctions, you should correct the problem as quickly as possible to ensure your safety and that of others on the roadway. Malfunctioning headlights impair your ability see the road, traffic conditions and pedestrians in low light conditions. Replacing and adjusting headlights is usually a do-it-yourself project.
Troubleshooting Faulty Headlights
Four issues can prevent the headlights from working as designed. These include the bulb, fuses, a switch or the electrical harness. Fixing a malfunctioning headlight is usually a process of elimination. Start with the simplest solution to determine whether it corrects the problem. If not, you should move to the next step. The problem may be as simple as changing a burned-out bulb, or it may require more extensive troubleshooting to identify the cause.
Inspect the Bulb
If one headlight is not working, open the hood of your vehicle to access the headlight assembly. Remove the non-working bulb to see if it is blown. Twist the socket to loosen it from the headlight assembly. Remove the bulb from the socket by pulling or twisting it. The bulb may be discolored. You may also be able to see if the filament is broken or melted. If the bulb appears to be in working order, remove the working bulb from the other side. Install it in the non-working light. Turn on your headlights. If the light illuminates, the original bulb is blown and must be replaced. If the bulb that you know works fails to illuminate or both headlights are out, you should proceed to the next troubleshooting step.
Check the Fuses
Locate the fuse box diagrams in your owner’s manual. The diagrams will identify the location of the fuse boxes as well as the layout of the fuses. Automakers typically mount the fuse box underneath the dash or inside the driver’s door. Another fuse and relay box will be mounted under the hood in the engine compartment. The layout diagram will show you where the headlight fuses are located and provide the ampere rating of the fuse. When you replace a fuse, you should install a new one with the same rating. Fuses of the same rating are often color-coded. Open the fuse boxes. Use the plastic, tweezer-like fuse puller to remove each fuse listed as controlling the headlights. There may be more than one fuse for each headlight located inside the vehicle and under the hood. Hold the fuse up to the light. If the fuse is blown, the metal filament in the middle will be broken. If you are unsure, install a new fuse that you know works. Turn on the headlights to see if they both illuminate. If one or more of the lights still does not work, move on to the next step.
Diagnosing an Electrical Short
Connect the negative lead from a voltmeter set to 12 volts to the negative terminal on the battery. Connect the voltmeter’s positive lead to the red wire on the headlight wiring harness. If there is no power reading, replace the headlight wiring harness.
Inspect the Switch
Disconnect the negative battery cable. Remove the headlights’ switch from the dashboard or steering column according to your repair manual. Unplug the wiring block from the back of the switch. Inspect the connections for discoloration. Gently clean the connections; reconnect the wiring block, and reattach the battery cable. If the headlights still do not work, replace the switch.
Replacing a Broken Headlight Assembly
The steps required to replace a broken headlight assembly will vary by model. They may include removing components underneath the hood that block the rear of the headlight as well as body panel trim pieces. You may also have to loosen the fender to access screws holding the side of the headlight in place. Consult your vehicle’s repair manual to find the exact steps.
Adjust the Headlights
Once both headlights work, you need to make sure that they are aimed properly. This ensures that you have maximum visibility and prevents the lights from shining into the eyes of oncoming drivers. Park your vehicle on a level surface with the front end about 1 foot from a wall. Use tape to mark a cross with a level horizontal line and a perpendicular vertical line. The intersection of the two pieces of tape should be approximately in line with the center of your headlights. The crosses will serve as your targets. Measure a distance 25 feet from the wall. Back up your vehicle so that the headlights are just behind this line.
Prop open the hood. Depending upon the year, make and model of your Toyota, the headlights will adjust using a screw or bolts. Use a screwdriver, a socket set or an adjustable wrench to turn the screw or bolts. There is a screw or bolt to adjust the horizontal angle of the headlights and another one to change the vertical angle. After turning your headlights on, turn the screw or bolt slowly in the direction required to adjust the headlights on target. The task is complete when the center of the beam is approximately 2 inches below the horizontal tape and aligned with the vertical stripe.
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