Tail Light and Headlight Assembly Buying Guide

Replace the whole headlight assembly when the lens, housing, reflector or mounts are damaged, or when water keeps getting inside. If the housing is sound and your car uses a replaceable bulb, a new bulb is usually all you need. This guide explains the difference between an assembly and a bulb, how halogen, HID and LED lamps differ, and what the DOT marking on a lens means. It also covers what is often left out of the box, driver and passenger sides, connectors, and aiming the beams after a headlight assembly replacement, with the same checks applied to tail lights.

Assembly or Just a Bulb?

An assembly is the complete lamp: housing, lens, reflector or projector, mounting tabs, adjusters and seals. Some also carry wiring, an HID ballast or an LED driver. A bulb is only the light source that sits inside it. If one low beam is out but the lens is clear and intact, check the bulb, the fuse and the connector before buying a whole unit.

Buy an assembly when the lens or housing is cracked, the reflector is damaged, a mounting tab has snapped, or water collects inside after rain. On many newer vehicles with LED lamps, the light source is built into the housing, so the assembly is the replacement part. Do not assume an LED board or driver is sold separately; check the parts catalog for your vehicle first.

Halogen, HID and LED Lamps

Halogen lamps use a replaceable filament bulb with a type code such as H11, 9005 or 9006. They are usually the least expensive and the easiest to service. Use the exact bulb type listed for your vehicle, because bases that look alike are not always interchangeable. HID, or xenon, lamps use an arc capsule fed by a ballast and often a separate igniter, and that circuit runs at high voltage.

LED lamps may use a plug-in bulb, a separate driver, or a board sealed into the housing. Match the assembly to the lighting your vehicle came with, since halogen, HID and LED trims of the same model often use different housings and wiring. A plug-in LED bulb placed in a reflector designed for halogen can scatter light and cause glare, so it is not an automatic upgrade.

DOT and SAE Markings on the Lens

In the United States, lamps must meet Federal Motor Vehicle Safety Standard No. 108, which covers lamps and associated equipment. Original and replacement headlamps are required to carry a DOT marking on the lens. Look for that marking molded into the lens itself instead of relying on a description that simply says DOT approved.

You may also see SAE codes on a lens, which identify the function or design category of the lamp. A DOT marking shows the maker certified the lamp. It does not show that the lamp fits your vehicle, so you still need to match the side, lighting type, connector and mounting pattern. State inspection rules can add their own requirements for color, aim and modifications.

What Comes in the Box

Treat a replacement assembly as housing only unless the listing clearly says otherwise. Many lamps arrive without bulbs, and an HID or LED unit may or may not include its ballast, driver or sockets. Read the included items before you order, and keep your old lamp until the new one works. Items worth checking for:

If you move bulbs from the old lamp, inspect them first. Never touch halogen bulb glass with bare fingers, because skin oil can create hot spots and shorten bulb life. Handle bulbs with clean gloves or a lint-free cloth, and replace halogen bulbs in pairs so light output and color match from side to side.

• Headlight bulbs or HID capsules
• LED boards or LED drivers
• HID ballast and igniter
• Bulb sockets and pigtail connectors
• Turn signal, side marker, parking and reverse bulbs
• Mounting hardware and seals

Side, Position and Connectors

Left and right are named from the driver's seat, so on a US vehicle the left lamp is the driver side and the right lamp is the passenger side. Tail lights add another choice: some vehicles split the lamp into an outer section on the body and an inner section on the trunk lid or liftgate. Confirm which section failed before ordering, and see our fitment help page if the side labels on a listing are unclear.

Compare the old lamp with the new one: mounting tabs, adjuster locations, bulb openings, vents and connector position. Count the terminals in the plug, but remember that pin layouts can differ between plugs that look the same. Never force a connector or splice around a missing terminal. A new lamp will not fix a blown fuse, a bad ground or a damaged plug on the vehicle side, so test power and ground with a meter if the old lamp looked fine.

Install Safely and Aim the Beams

Turn the lights and ignition off before unplugging a lamp, and disconnect the negative battery cable if the service procedure calls for it. HID systems carry high voltage, so wait the discharge time the manufacturer specifies and never probe that wiring with power applied. Some jobs require removing the bumper cover or wheel liner. If you raise the vehicle, support it on jack stands, and wear eye protection around brittle clips and broken lenses.

Aim the headlights after any assembly replacement, because small mounting differences move the beam. Follow the service manual: park squarely on level ground with correct tire pressures and the specified load, then check each low beam cutoff against a wall or with aiming equipment. Avoid aiming high, since glare dazzles oncoming drivers and can fail inspection. Vehicles with adaptive, self-leveling or HID projector lamps are better aimed by a shop with the proper equipment.

Before you finish, peel any protective film off the lens, confirm the gaskets and vent caps are in place, and test the low beams, high beams, turn signals, brake lights and reverse lights.

Choosing the Right Lamp Assembly

Start with your year, make and model, then read every row of the fitment table on the product page. Check the trim, body style and engine, and look for notes about lighting type, such as halogen, HID or LED, and any production date split. A projector or LED package can use a different assembly from the base trim of the same year, so the notes column matters as much as the year.

Browse all headlight assemblies or all tail light assemblies, or go straight to vehicle pages such as Chevrolet Camaro headlights, Chevrolet Equinox headlight assemblies, Silverado 1500 tail lights and Ram 1500 tail lights. Confirm the side, the lighting type and the included parts before you place the order.