How to clean headlights and restore cloudy, yellow lenses

Step by step: how to clean headlights and restore cloudy, yellow lenses

Safety first. Wear safety glasses, gloves and a dust mask while sanding, and work in a well-ventilated spot; 3M’s kit directions warn about sanding dust and compound vapors. Tape off the paint around the lens, because sandpaper will damage it. Never use these kits on glass headlights.

1. 1

   Wash the headlights

   Wash each lens with car wash soap and water, scrub off bugs and tar with a microfiber cloth, and rinse. Dry it and look again in good light: if it is now clear, you are done. If it is still yellow or foggy on the outside, keep going.

2. 2

   Check where the haze is

   Run a fingertip over the lens. A rough, chalky feel means the outer coating has oxidized, which a kit can fix. Fog or droplets inside the housing, or cracks, will not sand out; that headlight needs resealing or replacing.

3. 3

   Mask off the paint and trim

   Apply two layers of masking tape around the lens, covering the bumper, hood edge and trim. 3M’s directions recommend the double layer, because a slipping sanding disc will scuff paint. Do not tape over chipped or repainted areas, which can peel.

4. 4

   Sand off the yellow layer

   Start with the coarsest grit in your kit, about P500, using light to medium pressure and slow, even back-and-forth passes. Keep going until the whole lens has a uniform frosted white look with no glossy or yellow spots. The runoff will look yellow at first.

5. 5

   Refine the scratches with finer grits

   Switch to the next grit, around P800, and sand until the coarse scratches are gone, then finish with the finest, around P3000, misting the lens with water. The lens turns from white to a smooth, even haze.

6. 6

   Polish the lens clear

   Apply a dime-sized amount of polishing compound to the pad or cloth and polish in overlapping passes until the lens is clear. Add a little more compound if needed. If you still see sanding scratches, go back one grit and repeat.

7. 7

   Seal it with a UV protectant

   Wipe the lens clean and dry, then apply the kit’s UV sealant or clear coat exactly as directed, usually in one even pass. Let it cure for the time on the label, out of rain. This step is what keeps the lens from yellowing again within months.

8. 8

   Remove the tape and clean up

   Peel off the tape and wash any polish spatter off the paint with car soap. Check the beam against a garage door at night; it should be noticeably brighter and sharper.

Why do headlights turn yellow and cloudy?

Sunlight breaks down the protective coating on plastic headlight lenses, and the damaged surface turns yellow and scatters light. Most modern lenses are polycarbonate with a hard UV-resistant top layer; once that layer degrades, it has to be removed to get clarity back.

It matters for safety, not just looks. Consumer Reports, citing AAA testing, says badly clouded headlights can give off only about 20 percent of the light they produced when new, and that deterioration can start within three to five years.

Which headlight cleaning method should you use?

Match the method to the damage: light haze polishes off, heavy yellowing needs sanding, and damage inside the housing means replacement.

Consumer Reports found that restoration kits work, but the hazing usually came back after about a year, which is why the sealing step and a yearly touch-up matter.

Tips for drill-powered restoration kits

Drill kits are faster than hand sanding, but heat is the enemy. 3M’s kit directions call for a household drill at about 1,200 to 1,600 rpm; a faster drill can heat and smear the plastic.

• Hold the disc flat or at a very slight angle and keep it moving. Stopping in one place heats the lens.
• Use light pressure and let the abrasive do the work. Swap a disc once it clogs.
• Do not move on from the first grit until the whole lens looks evenly frosted; glossy patches mean yellow coating is still there.
• The process does not fix moisture or damage inside the lens, and large or very hazy lenses may need more than one kit.

How to keep headlights clear longer

Protect the new surface from UV and grit. Park in shade or a garage when you can, and wash the lenses whenever you wash the car.

Every few months, apply a plastic-safe UV protectant or a coat of car wax made for plastic. Avoid harsh solvents and abrasive bug sponges on the lenses. If you are already detailing, our guide to cleaning car seats covers the inside of the car.

Mistakes to avoid

• Skipping the masking tape and sanding through the clear coat on the bumper.
• Moving to a finer grit before the yellow layer is completely sanded off.
• Leaving out the UV sealant, so the lens yellows again within months.
• Running a drill too fast or holding it in one spot, which melts and smears the plastic.
• Trying to sand out fog that is inside the housing.
• Using a restoration kit on glass headlights.