Thursday, October 19, 2017 Detailed Auto Topics
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Modern vehicle styling uses exotic shaped headlamps to enhance appearance. Using glass to create these shapes is impractical, so they put a plastic in its place. This allows almost unlimited styles, but lacks the durability of glass, in resisting the elements. Dingy yellow headlamps often result after a few years.

The problem

Modern plastic headlights turn yellow over time

Dull yellow headlight lenses are not only unattractive, but they reduce the available light for the driver. Replacements are shockingly expensive, so many drivers tolerate a bad situation.

In the past, they used glass for headlamp lenses. Glass gives good service, because it resists the elements. This worked very well, when lights were simple round or square shapes. Molding glass into the exotic shapes on modern vehicles is very costly. Vehicle manufacturers use plastic to achieve the styling they want and cut their costs.

Surface roughness causes the yellow appearance.

Unfortunately, plastic does not resist the elements and over time the surface cracks and becomes discolored. Often this results in a dull yellowed appearance after a few years. Replacing the lens assembly solves the problem, but the cost is very high. They often price headlamp assemblies more than $400.00 per side.

A home remedy for yellow headlamps

With some work, we can often restore headlamps to good condition. This is not complicated, but requires care to avoid damage to the vehicle. Several companies sell kits to clean and polish headlamps, and in a pinch, toothpaste will also work. For those who would rather not attempt this, AGCO provides this service for a small cost.

For folks who enjoy this type work, we include easy-to-follow instructions.

Protect the surrounding paint

A shady place to work makes the job more comfortable and is necessary to prevent problems. Never attempt to restore headlamps in the direct sunlight. Sunlight can cause masking tape to stick to the paint and may create problems, by drying out the polishing compound.

Masking tape protects the painted finish when cleaning headlamps

Use a masking tape to protect the paint surrounding the headlamp. A slight slip when sanding or polishing can leave a permanent scar on the finish. Standard two-inch masking tape does a good job, and a double layer affords more protection. On repainted vehicles always test the tape in an unobvious area before applying elsewhere. Masking tape can damage paint that does not firmly stick to the surface. Rubbing the tape across a pant leg, before applying, will reduce adhesion and may help.

Also never allow masking tape to remain on the paint surface more than an hour or so. The adhesive in tape can be impossible to remove if left on the surface too long. Remove all tape and use car polish if necessary to remove any glue traces immediately after competing the job.

Smoothing the surface

Lightly wet-sanding improves the surface finish

To remove the damaged top layer, wet sanding is necessary. Some advise that a power tool makes the job easier. Hand sanding is as effective and by far a safer choice, for the beginner.

Start with an 800-grit, wet or dry sand paper. This is coarse and will quickly remove the rough layer. Wet the surface with a slow running hose or spray bottle and sand evenly in a circular motion. Sanding in a straight direction may cause scratches that are difficult to remove.

Frosted surface after wet sanding the headlamp

Lightly sand, continuously applying water to wash away the removed material. When we properly remove the yellow, the surface will appear frosted white and even across the lens.

To remove the scratches from the initial sanding, we use a finer grit paper. A higher grit number shows a finer finish and we use 1500-grit next. Sand the entire surface in an orbital pattern, keeping the paper wet with water. When complete the surface should appear even and more transparent than before.

Finish with a final sanding using a 3000-grit sand paper. As before, sand the entire surface keeping the paper wet. The lens should now appear clear but dull in appearance. Any uneven spots require additional sanding.

Bringing back the shine

A headlight restoration kit will include a polish we use to remove the sand scratches and make the lens shine. Some products include two polishing products for an even finer appearance. In a pinch, corn starch will also serve as a polishing material, if mixed with water.

Polishing restores the shine to the headlamp assembly

Polishing it by hand is safest or for the more adventurous a slow turning drill or polisher is much faster. By hand, we use a circular motion, starting at one side of the lens and working to the other. This takes time but is safer for a beginner.

A drill that turns 800 RPM or less will speed the process. A faster turning polisher may burn the plastic and ruin it, so be careful. We need a polishing pad and it must be kept in constant motion. Holding the spinning pad in one spot may burn the plastic. Practice with the polisher, on something other than the vehicle, until the technique is mastered. Being safe rather than sorry is always best.

After polishing the headlamps appear almost like new

After polishing the lens, it should appear almost new, clear and shiny. Any dull spots require additional polishing. Remove the tape, wash the area thoroughly and enjoy the results.





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