Cloudy Headlights: Restore or Replace?

Drive around Reno for a few minutes and you will see dozens of cars with yellowed, foggy headlights. It is one of the most visible effects of high desert sun. It is more than cosmetic. A cloudy lens scatters the light, which cuts how far you can see at night and can throw glare at oncoming drivers. Here is how to decide between restoring and replacing, and where the bulb fits in.

At a glance

• Most modern headlight lenses are polycarbonate with a factory UV coating.
• When the coating fails, sun and road sand haze the plastic.
• Restoration works on outside haze; inside haze and moisture need a new housing.
• Dim lights can also be an aging bulb, which is a separate fix.

Why do headlights turn yellow and cloudy?

Headlight lenses on most cars since the 1990s are polycarbonate plastic, which is light and impact resistant but breaks down under ultraviolet light. Factories apply a hard UV coating to protect it. Over years, sun, heat, sand and road chemicals wear through that coating, and the plastic underneath starts to oxidize, turning yellow and rough. Northern Nevada speeds it up: lots of clear, sunny days at about 4,500 feet of elevation, where UV is stronger, plus wind-blown sand and winter road treatment.

When does restoration make sense?

When the damage is on the surface. Run a finger over the lens; if it feels rough and the haze is evenly spread on the outside, restoration can work. The process sands away the damaged layer in progressively finer steps, polishes the plastic clear, and finishes with a UV-blocking sealant or clear coat. The last step is the one that matters most. Without a new UV layer, a restored lens can cloud up again quickly in desert sun.

Restoration kits are sold for home use, and many detail and body shops offer it as a service.

• Haze is on the outside of the lens
• No cracks, chips or broken mounting tabs
• No water droplets or fog inside the lens
• The reflector behind the lens is still bright and silver

When is replacement the better choice?

When the problem is inside. Fog or droplets inside the lens mean the seal has failed, and moisture will keep coming back. A reflector that has turned dull or flaked from heat will not reflect light properly no matter how clear the lens is. Cracks, broken tabs and deep pitting also point to a new assembly. Replacement assemblies are available from dealers and aftermarket suppliers, and installing them ranges from simple to bumper-off depending on the car.

Could it be the bulb instead?

Sometimes. Halogen bulbs dim as they age, well before they burn out, and a car with a clear lens and an old bulb can still have poor lighting. NHTSA's vehicle lighting pages point out how much headlights matter for seeing hazards at night. If one side looks dimmer or yellower than the other, compare the bulbs. Our headlight bulb guide covers bulb types, and the dim or yellowed headlights page helps sort lens from bulb.

What we do about it in the bay

During the multi-point check at our four service centers, the technician checks that headlights, high beams, brake lights and turn signals all work and looks at the condition of the lenses. If a bulb is out or dim, our headlight and tail light bulb service replaces it with the right type for your car, and you see the old one. If the lens is badly hazed or has moisture inside, we point it out and tell you the options above, since lens restoration and housing replacement are done by detail and body shops.

Drive in to Mae Anne Avenue, Longley Lane, College Parkway or US 395 in Gardnerville. Winter evenings come early, and clear lights matter on unlit roads like US 395 through Washoe Valley.