Headlight Bulb Replacement: Bulbs, Assemblies, Aim and Cost

What does headlight bulb replacement involve?

A headlight has two main parts: the bulb that makes the light, and the assembly (the housing and clear lens) that shapes and aims it. Most of the time, when one headlight goes dark, the bulb has burned out and only the bulb needs replacing.

The assembly matters too. AAA Northeast’s mechanic column explains that headlight bulbs don’t tend to dim, but lenses can, because the sun’s UV rays oxidize them. Bulbs themselves can fail early; the same column says they should last five years or so, but road and climate conditions often break the filament sooner.

What are the signs you need a new bulb or assembly?

• One headlight out. The classic sign of a burned-out bulb. Check both low and high beams.
• Light that comes and goes. This can be a failing bulb, but Wagner, a lighting maker, notes that a corroded socket or faulty wire can also stop a bulb from lighting. If both headlights flicker or dim together, the cause is more likely electrical; see our guide to headlights flickering.
• Yellow, cloudy lenses. A new bulb won’t fix a hazy lens. In AAA testing, cloudy headlights produced only 20% of the light of new ones, and lenses can start to deteriorate in as little as three to five years.
• A dashboard bulb-out warning, on vehicles that have one.

AAA found that replacing clouded assemblies with original-equipment parts restored light output to 100%, aftermarket assemblies restored 83% to 90%, and restoring the old lenses returned roughly 70%.

Is it legal to drive with a headlight out?

Rules vary by state, but you should expect to need two working headlights. AAA’s car care guide puts it plainly: driving at night with any light out is illegal just about everywhere, and even a burned-out license plate or side marker light can get you a ticket. It also cites statistics indicating nearly twenty percent of vehicles on the road have one or more exterior lights not working.

As one example of how a state writes this, California Vehicle Code section 24400 requires a car to have at least two headlamps, one on each side, and to be driven with at least two lighted headlamps during darkness or inclement weather. It defines inclement weather as conditions where you can’t clearly see a person or vehicle 1,000 feet away, or where rain, snow, fog or mist keep the wipers running continuously. Check your own state’s rules, especially if your state has a periodic safety inspection.

There is a safety reason behind the law. AAA’s maintenance checklist suggests walking around your vehicle each month to confirm every light works, noting that a burned-out headlight makes it harder for other drivers to see you and raises your risk of a collision.

Can a mobile mechanic replace a headlight bulb in the driveway?

Yes. A bulb swap is well suited to mobile service, and so is replacing a complete headlight assembly on many vehicles. How long it takes depends on the car. AAA notes that replacing bulbs on some late-model cars can be tricky, and a special tool may be needed to remove a lens or trim pieces to reach the bulb. AAA Northeast adds that some bulbs are expensive, or expensive to get to.

What usually needs a shop is aiming. AAA’s guide says that when headlights are replaced, or after any front-end work, they should be accurately aligned and aimed by a repair shop with the proper equipment. Ask the mechanic whether your job calls for it, especially if a whole assembly is replaced. AAA also notes that some upscale vehicles use HID headlights with auto-leveling, which is another reason to give the mechanic your exact model and trim before the visit. See what a mobile mechanic can and can’t do for the general limits.

What does the job involve?

1. Confirm the cause. The mechanic checks whether it’s the bulb, the socket and wiring, a fuse or relay, or the lens.
2. Match the part. The right bulb type or assembly is confirmed for your year, make, model and trim. Your owner’s manual lists the bulb type.
3. Get access. On many cars the bulb is reached from under the hood; on others, trim or a lens has to come off first.
4. Fit the new bulb. Wagner advises not touching the glass of a new halogen bulb, because skin oil can make it heat unevenly and burn out early; it also suggests checking the connector for looseness or corrosion before installing. AAA advises protective glasses, because a halogen capsule is pressurized and can shatter.
5. Test. Low beams, high beams and any bulb-out warning are checked, and the beam pattern is checked.

Should both sides be replaced? Wagner recommends changing headlights in pairs, since the other bulb is likely to burn out soon. AAA Northeast calls pairs recommended but not necessary. It’s your call, and doing both on one visit saves a second trip.

How much does headlight bulb replacement cost?

Headlight bulbs and assemblies are not in this site’s standard price table. The price swings widely between a basic halogen bulb and a full assembly, and with how hard the bulb is to reach, so the mechanic quotes after looking. These ranges from the site’s price table, based on prices that mechanics we list publish on their own websites, still apply:

Because a bulb swap can be a small job, the trip fee can be a big share of the bill. It often makes sense to book it alongside other work, such as a mobile oil change. See mobile mechanic cost for the full table.

What should you ask before booking?

• Is it the bulb, or could it be the socket, wiring or lens?
• How is the bulb reached on my car, and does anything need to come off?
• Will you replace both sides, and what does each option cost?
• If the assembly is replaced, will the headlights need aiming at a shop?
• Is there a trip fee, and can I add other small jobs to the same visit?

A mechanic who can see the car will know more than any guide.

What to do next

A headlight out is worth fixing before your next drive after dark. Find a mobile mechanic in your city, or send a request with your year, make, model and trim, which light is out (low beam, high beam, left or right), and whether the lenses look cloudy.