Headlight restoration or replacement? – A complete guide

If you’ve ever driven in the rain, you probably have noticed that your headlights can get pretty cloudy, especially on older cars. This is because the water can cause a film to build up on the headlight, which can reduce your visibility. There are other factors that can result in cloudy or dimmed headlights as well. We will guide you through the causes and how headlight regeneration or restoration can revive your headlights, and when you may need to get a replacement headlight.

Can foggy headlights result in an MOT failure?

Yes, foggy or cloudy headlights can result in a “Major” failure on an MOT test.

The rule for headlights states that every lamp unit needs to be clean, clear and should allow the light to pass through unobstructed. If your headlights are yellow, hazy or oxidised then this will affect the beam pattern / light output.

This means that anything that reduces the light output will result in a “Major” fail on an MOT test. If a headlight lens has oxidised or ‘slightly defective’ this can result in a “Minor” fail on an MOT test.

What causes hazy or cloudy headlights?

Hazy or cloudy headlights can be caused by a number of external factors, here is a selection of the top causes:

  • Water vapour
    Headlights are manufactured and fitted with a watertight seal. Over time, this seal can rupture through wear and tear, causing water to enter and resulting in condensation. These water droplets then scatter beams of light which reduces visibility.
  • Oxidisation
    A common cause of hazy headlights is oxidisation. Acrylic headlights oxidise when exposed to UV light, i.e. the sun. These are specialised lenses that are coated in a coating to help prevent oxidising. The casing becomes yellow with age as the coating wears off and UV light oxidizes it.
  • Road debris and normal wear and tear
    As you cruise down the road, you kick up gravel, road salt, and other debris. In addition to wearing down the topcoat, this causes pits and scratches on your headlights, resulting in a cloudy appearance.

When to regenerate or replace headlights?

When you have to replace or restore / regenerate headlights will depend on the state as well as the type of headlights. Most headlights that are cloudy or hazy can be restored by polishing to bring back their clarity. If restoration does not help to bring the headlights back to a state where light can pass unobstructed you will likely be left with no choice than replacing the headlights.

In some cases, the headlight glass may be broken which generally cannot be restored. As any cracks can distort the beam emitted you will likely then have to replace the unit.

On some newer models equipped with sealed HID or LED light units headlight restoration is often not possible and the only option is a replacement of the unit. Even if it’s just the glass that is hazy you can generally not carry out internal polishing or restoration. Same goes for when it’s just the LED light that’s broken, you will normally have to replace the whole unit.

Can you repair cloudy or faulty headlights?

This depends on the extent of the damage but in most cases, foggy or cloudy headlights can usually be repaired with a headlight restoration kit.

There are a few ways to repair foggy or cloudy headlights. One way is to use a headlight restoration kit. These kits come with a sanding block and a polishing compound. You will need to sand the headlight lens to remove the haze and then polish it to restore the clarity.

Another way to repair foggy or cloudy headlights is to use a headlight sealant. This is a clear coat that you can apply to the headlight lens. It will seal in the clarity and prevent the headlight from getting foggy or cloudy again.

If your headlights are severely foggy or cloudy, you may need to completely replace them. ClickMechanic can help with the replacement, repair and restoration of headlights right at your doorstep.

In the case of foggy headlights failing the MOT test, a mobile mechanic can fix it right on your driveway without having to go to a garage.

How to fix cloudy headlight: DIY headlight regeneration and restoration

Car headlight wash and restoration

There are a number of DIY treatments using household items that can help with the regeneration and restoration of headlights

The toothpaste method

Toothpaste has abrasive components that can remove surface scratches and scrapes on your headlight casing.

  1. Start with a clean surface, use car shampoo to clean the headlight and let it dry
  2. Using a soft toothbrush or cloth, scrub the surface
  3. Rinse with warm water and wash off with a soft cloth

The baking soda method

  1. This method follows the steps mentioned above but using a paste of baking soda and water paste
  2. The paste can then be applied to the headlights and allowed to sit for a few minutes before scrubbing it with a sponge
  3. Make sure to wipe off with a clean cloth

The sandpaper method

  1. Use good quality masking tape to tape off the edges and protect the paintwork
  2. Wet the surface of the headlight with clean water
  3. If there are visible scratches on the surface, use wet 400 grit sandpaper and smooth across the surface of the headlight – be sure to avoid any harsh motions that dig into the casing
    1. The higher the grit number so use your judgement to use the right grit sandpaper
  4. Make sure to check the more gritty areas on the casing
  5. Once this done, use higher grit sandpaper like 600, and 800 or above grit sandpaper if needed
  6. Use a soft towel to finish off and clean the surface
  7. As an extra step, you can also finish off with buffing the surface with polish
    1. Use polishing compound on a flannel cloth and polish the surface of the headlight in circular motions

Headlight restoration kits

Headlight restoration kits or headlight regeneration kits are all-in-one kits that aim to restore acrylic-based headlights to its original state. If the headlight is extremely weathered, the kit may not be able to restore it to its original condition. In this case, it is best to have it replaced professionally at your local garage or mechanic.

Most kits on the market come with the following contents:

  • Restoration compound
  • Various buffing or sanding pads (usually drill operated so you’ll need a high-speed drill)
  • Microfibre cloth

The instructions provided with the kit are vital to achieving a successful result. Follow all safety precautions such as wearing gloves or safety goggles if needed.

Headlight polishing kits

If you don’t want to use a drill, another option is a clean and coat headlight restoration or regeneration kit.

  1. The first step is to use the cleaning solution to remove oxidation
  2. Once the oxidation is removed, the second step in the kit is to spray a coat that reveals a clear headlight
  3. You can use multiple coats to improve the clarity of the headlight

How to prevent headlights or headlamps turning cloudy or yellow?

Car with yellow headlight

Rule 226 of the Highway Code in the UK states, “You must use headlights when visibility is seriously reduced”, with ‘seriously reduced’ further defined as when you are able to see less than 100 metres in front of you. Cloudy headlights can result in a reduction of visibility on the road thus posing a safety risk to you and other drivers, so it’s crucial that you take good care of them. Some ways you can prevent headlights from turning cloudy or yellow include:

Parking your car in the shade

If possible, park your car in a shady place such as a garage or under a tree. In cases where you don’t have that option, parking outside with your headlights facing away from the sun can reduce UV exposure and slow the oxidation process.

Paying attention to the headlights during a car wash

Wash the headlights with proper car soap or shampoo to clean away dirt and chemicals that accelerate fogging of the headlights. If you’re waxing the exterior paint of your car don’t forget to apply it to the headlights as well which can add an extra layer of protection. Wax can help prevent debris from sticking to the surface of the plastic. Make sure you check that the wax you’re using is suitable to be used on plastic surfaces.

How much does it cost to replace a headlight?

A headlight assembly replacement can quickly cost over £200 to £1000. The cost will depend on your make and model of car, and whether you’re using aftermarket or OEM parts.

Unfortunately, if headlight restoration or regeneration cannot remedy any issues around cloudy headlights, or if your headlight is simply cracked or broken a replacement will often be the only option.

Also, newer models are often equipped with sealed headlight units with LED and HID lights which are particularly expensive and come in at the higher end of the scale, from £500 to £1000. You will usually have replace the whole headlight unit if there’s something wrong.

Remember, you can always leave the job to a garage or mobile mechanic if you’re not so confident doing it yourself or it seems too complicated. Depending on whether you need to replace a bulb, restore or replace the headlight unit, and what kind of bulbs you need, the cost of restoration and repair will vary. You can get a price based on the make and model of your vehicle on ClickMechanic.