Editing Headlamp (section)

== Care ==
Headlamp systems require periodic maintenance. [[Sealed beam]] headlamps are modular; when the [[Electrical filament|filament]] burns out, the entire sealed beam is replaced. Most vehicles in North America made since the late 1980s use headlamp lens-reflector assemblies that are considered a part of the car, and just the bulb is replaced when it fails. Manufacturers vary the means by which the bulb is accessed and replaced. Headlamp aim must be properly checked and adjusted frequently, for misaimed lamps are dangerous and ineffective.<ref name="aim"/>

Over time, the headlamp lens can deteriorate. It can become pitted due to abrasion of road sand and pebbles and can crack, admitting water into the headlamp. "Plastic" ([[polycarbonate]]) lenses can become cloudy and discoloured. This is due to oxidation of the painted-on lens hardcoat by ultraviolet light from the sun and the headlamp bulbs. If it is minor, it can be polished out using a reputable brand of a car polish that is intended for restoring the shine to chalked paint. In more advanced stages, the deterioration extends through the actual plastic material, rendering the headlamp useless and necessitating complete replacement. Sanding or aggressively polishing the lenses, or [[plastic headlight restoration]], can buy some time, but doing so removes the protective coating from the lens, which when so stripped will deteriorate faster and more severely. Kits for a quality repair are available that allow the lens to be polished with progressively finer abrasives, and then be sprayed with an aerosol of ultra violet resistant clear coating.

The reflector, made out of vaporized aluminum deposited in an extremely thin layer on a metal, glass, or plastic [[substrate (materials science)|substrate]], can become dirty, oxidised, or burnt, and lose its [[specular reflection|specularity]]. This can happen if water enters the headlamp, if bulbs of higher than specified wattage are installed, or simply with age and use. Reflectors thus degraded, if they cannot be cleaned, must be replaced.