Symptoms
- One headlight doesn't light up while the other works fine
- Reduced visibility on one side of the road at night
- May have flickered before going out completely
- Other lights on the car work normally
Likely causes
- CommonBurned out headlight bulbBulbs simply wear out over time, especially halogen bulbs after a few years of use.
- PossibleLoose or corroded bulb connectorA poor connection at the bulb socket can prevent it from lighting even if the bulb is fine.
- PossibleMoisture inside the headlight housingWater intrusion can cause corrosion at the bulb contacts or even damage the bulb.
- Less commonBlown fuse for that specific headlightSome vehicles fuse each headlight separately, so one fuse can affect just one side.
What to do
- Confirm it's actually the bulb by testing high and low beam, since some vehicles use separate bulbs for each.
- Check the fuse box for a blown headlight fuse specific to that side and replace with the correct amperage.
- Open the hood and locate the back of the headlight housing to access the bulb connector.
- Unplug the connector, remove the old bulb, and inspect it for a broken filament or dark, discolored glass.
- Install a new bulb of the correct type without touching the glass with bare fingers, which can shorten its life.
- Reconnect the plug firmly and test both high and low beam before closing everything up.
- Check the headlight housing for any moisture or fogging that could indicate a seal problem.
- Have a shop replace the bulb if it's in a hard to reach spot requiring extra disassembly.
Tools and parts
- Gloves (to avoid touching bulb glass)
- Screwdriver (varies by vehicle)
Replacement headlight bulbSearch: “headlight bulb for [your car make model year]”
When to call a pro
If the headlight housing has visible moisture or fogging, have it checked, since a bad seal can damage bulbs and wiring repeatedly.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.