Is your car headlight not working, dim, or needing to be replaced entirely? We’ve got you covered as we look at car headlight repair!

An Important Set of Car Lights

2023 Ford F-150 - ford.com
2023 Ford F-150 - ford.com

Cars feature a ton of different lights nowadays. You’ve got your dome lights, gauge cluster warning lights, entry puddle lights, illuminated USB ports, various backlit buttons, and that’s all just on the inside. Today we’re looking at maintaining, restoring, and repairing some of the most important lights found on the outside of the car, the headlights. Brake lights are equally as valuable on the road, but we’re focusing on those forward-facing lights for this one. Headlights help you navigate through dense fog and dark nights when visibility is a necessity. They not only help you see the roadway, but headlights also act as bright beacons that alert other drivers to your location on the road in low visibility or dark conditions.

However, headlights are prone to burning out, losing their luster, or completely breaking leaving you with less visibility when you need it. Driving without properly maintained or working headlights can pose a risk to not only yourself but other drivers. Plus, you might end up with a ticket should a law enforcement officer find you driving with only one headlight working. So, let’s look at different ways to repair and keep your headlights working.

Car Headlight Inspection

Inspecting headlights on a car
Inspecting headlights on a car

It’s a good idea to give your car’s headlights a look from time to time. It’s better to be aware of an issue early on before it grows into driving without some of your lights when you need them. All you really need to do to inspect your headlights is to pop the hood and turn the car on. Then you can look over the different parts that make the headlight assembly a working whole.

Turn On and Inspect Bulbs

Let’s start by inspecting the bulbs. Headlight bulbs can burn out just like any regular household light bulb, so we’ll want to turn on the vehicle and make sure that they all light up. When the vehicle is on, make sure your lights are turned on and hit the hazards so that you can check that the blinkers come on too. If you find that one or more of your light bulbs aren’t coming on, they’ll need to be replaced. If the whole headlight doesn’t turn on, that could mean an issue with the wiring harness which we’ll cover coming up.

Check Headlight Clarity and Condition

2023 Mercedes-Benz AMG GT headlight - mbusa.com
2023 Mercedes-Benz AMG GT headlight - mbusa.com

If the lights are all illuminated, check the headlights for clarity. Modern headlights use thick, polycarbonate plastic in their construction that makes the clear lens durable and scratch-resistant, but they unfortunately suffer from fogging. This fogging of the plastics is caused by the sun’s UV rays breaking down the outer layers of the plastic degrading the clarity. Light can still pass through these foggy headlights, but the bulbs inside won’t be as effective in lighting the way. There are a couple of different ways to combat fog, but it’s an issue that can reoccur even after correcting it.

Also, look for any significant damage to the headlight assembly itself such as deep scratches, cracks, or missing pieces. Some headlight damage can be fixed or be left alone without causing any issues with functionality, but significant damage should be corrected by replacing the headlight assembly as a whole. For instance, if there’s a portion cracked enough to let water into the assembly, that can cause a host of potential issues. Not to mention that an actual hole in the lens can let debris in and hurt the effectiveness of the headlight or even lead to the bulbs being broken inside the assembly.

Make Sure Headlight Brackets are In Good Shape

Headlight bracket
Headlight bracket

Headlights are held in place by special brackets that secure it to the vehicle. These brackets are commonly made with plastic and can break which can allow the headlight to vibrate and jostle while driving. Continuing to drive with a broken headlight bracket can result in stress to the other brackets leading to them breaking or the added vibration can loosen the bracket bolts holding the headlight in place. In extreme instances, all this can lead to the headlight assembly actually falling out of the vehicle should every secure point fail. Best to address a broken headlight bracket when it’s noticed.

Inspect the Headlight Wiring Harness

Check that the wiring harness isn’t loose, disconnected, or severed as this could be the culprit if your whole headlight isn’t coming on. If the wiring harness is loose from its connector to the vehicle, the light could be unpowered. With the vehicle off, try disconnecting and reconnecting the wiring harness and test the lights again. If it is still loose and not turning on then the connector may be faulty and the wiring harness will need to be replaced. You’ll also need to replace the wiring harness if you notice that it has disconnected from the bulb sockets or the connector to the vehicle. Even if all of your lights come on, it’s good to check that the wiring harness doesn’t have any frayed wires from age or possibly from critters getting under the hood while parked.

Foggy Headlight Restoration

Foggy headlights
Foggy headlights

There are a couple different methods to alleviating foggy headlights. First are the at-home remedy options like scrubbing the foggy headlight with toothpaste or a baking soda and water mixture. The abrasiveness of these solutions is enough to remove the foggy exterior without seriously damaging the headlight finish. All you need to do is:

  • Clean off the headlight surface.
  • Use masking tape on the areas surrounding the headlight as to not damage the vehicle’s paint while scrubbing.
  • Scrub the toothpaste or baking soda solution in gentle yet firm circles around the headlight.
  • Rinse the product off with water and take note of the results.
  • Repeat the process until you see the fogginess is alleviated.
Headlight taped off while being cleaned
Headlight taped off while being cleaned

There are also numerous products out there from brands like Rain-X, Sylvania, and Turtle Wax that are dedicated to helping clear up that foggy headlight. Each kit varies, but they follow some of the same steps while featuring different formulas to get the same desired result:

  • Clean off the headlight surface.
  • Apply the surface activator to the headlight.
  • Rinse the headlight.
  • Dry the headlight surface.
  • Use masking tape on the areas surrounding the headlight as to not damage the vehicle’s paint while sanding or from the product solution.
  • Wet sand the headlight with the provided lower grit sandpaper (usually about 400 grit) in a circular motion. You can wet sand by running water over the headlight while you work or by actually dipping the sandpaper in water.
  • Wet sand the headlight with the provided higher grit sandpaper (usually about 800 grit) in a circular motion.
  • Wet sand the headlight with the provided highest grit sandpaper (usually about 2000 grit) in a circular motion.
Headlight being cleaned
Headlight being cleaned
  • Use the provided polish product and scrub it in a circular motion over the headlight with a rag.
  • Rinse the headlight.
  • Dry the headlight surface.
  • Apply the surface activator to the headlight again.
  • Rinse the headlight.
  • Dry the headlight surface.
  • Apply the UV clear coat product to the headlight using horizontal wipes working from the top of the headlight to the bottom.

It’s important to note with these products that you’ll want to keep the car in a dry, covered location as getting them wet or encountering foreign substances after the final application can mess up the finish. Another thing to keep in mind when performing any of the above headlight restoration methods is to take your time and work diligently. You don’t want to rush it and end up having to buy a whole new headlight assembly because of a damaging error while trying to fix some fog.

Replacing a Burnt-Out Headlight Bulb

New headlight bulb
New headlight bulb

Headlight bulb replacement is somewhat of an easy task with today’s modern headlight assemblies. If you encounter a burnt-out bulb, it’s best to replace all the bulbs as the adjacent bulbs will likely burn out soon too. Not all headlight assemblies are exactly the same, but they each follow similar steps:

  • Pick up your replacement bulbs prior to removing the old bulbs. You can find bulb identification tools on the web or in store that will tell you which version of bulbs from different brands go to your specific make, model, and year of vehicle.
  • Pop the hood and make sure that the vehicle is off.
  • Identify which bulb you are replacing and locate its socket on the back of the headlight assembly.
  • Once you find the bulb socket location on the back of the headlight assembly, figure out if you’ll need to move the air intake or battery to access it. If your access to the socket isn’t blocked, carry on to the next step. If there is equipment blocking access, carefully disconnect the piece of equipment blocking access to the socket, taking care to not lose necessary bolts and remembering the position of the equipment to reinstall later.
  • Detach the socket from the bulb by pressing its locking tab to release it and pulling it away by the socket. Be careful not to pull the socket by the wires as they can dislodge and result in the need for a new wiring harness.
Switching out a headlight bulb
Switching out a headlight bulb
  • In most vehicles, you should be able to grab the bulb housing and twist it to the left to dislodge it from the headlight assembly and slide it out. Some vehicles may have a retaining ring or secure clip that will have to be loosened or removed before the bulb can be fully removed.
  • Discard the old bulb.
  • Carefully remove the new bulb being sure not to touch the glass portion with your bare fingers as the oils can create a hot spot leading to the replacement burning out earlier.
  • Slide the bulb into the empty headlight opening and twist it to the right to secure it.
  • Reattach the headlight socket to the installed bulb making sure its locking tab activates and is securely connected.
  • Repeat for all other burnt-out bulbs.
  • Once all the burnt-out bulbs have been replaced, turn on the vehicle to ensure that all of them are working properly.

Should one of the new bulbs not light up, turn off the vehicle and make sure that the socket is properly connected to the bulb and try turning the vehicle on again. If the bulb still doesn’t come on, try another replacement bulb. In the event that the second replacement bulb does not work, you may have an issue with your headlight wiring harness which we’ll cover next.

Replacing the Headlight Wiring Harness

Headlight wiring harness - TRQ on youtube.com
Headlight wiring harness - TRQ on youtube.com

Replace your headlight’s wiring harness shouldn’t be a recurring task with your vehicle. If you have to keep replacing your wiring harness, you may be facing electrical issues you’ll want to take up with a certified mechanic. Other common issues that may result in the need to replace the wiring harness is improperly handling the wires when replacing bulbs or dealing with a pest living in your garage who has been chewing the wires. Whatever the case, here’s what you’ll need to do in the event that you need to replace a headlight wiring harness:

  • First, purchase the correct headlight wiring harness for your specific vehicle.
  • Pop the hood.
  • Disconnect the headlight wiring harness main connector from the vehicle by lifting its locking tab to release it and pulling it away by the connector.
  • Remove the various sockets from the bulbs by pressing their locking tabs to release the sockets and pull them away.
  • Discard the old wiring harness.
Light bulbs attached to new wiring harness - TRQ on youtube.com
Light bulbs attached to new wiring harness - TRQ on youtube.com
  • Begin installing the new wiring harness by connecting each of the sockets to the correct bulbs making sure their locking tabs activate and are securely connected.
  • Connect the headlight wiring harness main connector to the vehicle connector. Make sure the connection is secure.
  • Start the vehicle and check that the lights come on.

Should the light not come on after replacing the wiring harness, turn off the vehicle and check that each of the sockets and the main connector are seated correctly and try again. If the headlight light still doesn’t come on, then you may have a different faulty wire somewhere else upstream that will need to be identified and replaced. Otherwise, it could also be a larger electrical issue that needs to be diagnosed by a professional.

Replacing a Headlight Assembly

Removing headlight assembly - O'Reilly Auto Parts on youtube.com
Removing headlight assembly - O'Reilly Auto Parts on youtube.com

While you can use sealant on a crack in the headlight or melt the plastics of a busted bracket back together, the structural integrity of the headlight has been compromised. While these quick fixes to damage will work for a short time, the most effective way to correct a damaged headlight assembly is to completely replace it. That may not be the cheapest answer, but a new headlight will be without flaws and come with warranty coverage in some instances. You could even use the necessity of replacing a broken headlight assembly as an excuse to get yourself a nice set of aftermarket projector headlights.

So, let’s get into the steps need for replacing most headlights:

  • Start by purchasing the new headlight assembly. You can purchase a single assembly if only one side is broken, but it’s best practice to purchase the pair.
  • Once you have the new headlight assembly, you’ll want to pop the hood.
  • Before removing bolts from the old headlight, you’re going to need to remove the front bumper to gain better access to the different areas that the headlight is secured to.
  • Your vehicle’s manual should show the various front bumper connections you’ll have to work with. Carefully unscrew bolts from the bumper taking note of which ones go where so that you can properly reinstall it later.
  • Once the bumper is removed, you should have access to the portion of the headlight assembly that was covered by the bumper.
Bulb to be detached from headlight assembly - O'Reilly Auto Parts on youtube.com
Bulb to be detached from headlight assembly - O'Reilly Auto Parts on youtube.com
  • If you have an air intake or battery that is close to the rear of the headlight assembly, you may need to remove the equipment to properly remove the headlight.
  • Detach the sockets from the bulbs by pressing their locking tabs to release the sockets and pull them away. Be careful not to pull the sockets by the wires as they can dislodge and result in the need for a new wiring harness.
  • Remove the bulbs using the same process mentioned above for replacing the bulbs.
  • In most vehicles, you should be able to grab the bulb housing and twist it to the left to dislodge it from the headlight assembly and slide it out. Some vehicles may have a retaining ring or secure clip that will have to be loosened or removed before the bulb can be fully removed.
  • Begin removing the various screws holding the headlight assembly in place. There are typically three points of contact to address with most setups.
  • Once all the screws are out, pull the headlight assembly towards yourself to remove it.
  • Grab the new headlight assembly and slide it into the empty spot.
  • Screw down the new headlight assembly using the same locations from the previous headlight.
  • Slide the bulbs into the empty headlight opening and twist them to the right to secure them.
Attaching new headlight assembly
Attaching new headlight assembly
  • Reattach the headlight sockets to the installed bulbs making sure their locking tabs activate and are securely connected to the correct bulb.
  • Repeat the headlight replacement steps for the other side of the vehicle if you purchased a new pair.
  • Turn on the vehicle and switch on the lights to make sure they are working properly.
  • Aim the vehicle at a blank wall so that you can see the headlight beams.
  • Mark the desired beam height with a horizontal length of masking tape on the wall.
  • Locate the various adjustment screws found behind the headlight assembly and slowly turn them clockwise to raise the headlight upwards or counterclockwise to lower it. Carefully adjust each adjustment screw on each headlight so that the most intense point of their headlight beam lines up with the masking tape.
  • Once both lights are properly adjusted, turn off the car, reinstall your front bumper, and close your hood. You should be good to go!

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Jesse McGraw

Jesse McGraw brings his life-long car obsession into his writing. A fun childhood that involved growing up around race tracks, working on a rusty ‘99 Dodge Dakota held together by zip ties, and collecting Hot Wheels developed into a strong appreciation for automotive history. If there is an old, obscure, or rare car, he wants to know about it. With a bachelor's degree in Web Development & Design from Dakota State University, Jesse can talk shop about car or computer specs, focusing on classic cars, imports, and car culture.

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