Repair & Maintenance

Troubleshooting Common Headlight Problems

Keep your headlights shining bright

Whether you’re driving home from a late night at work or get caught in a rainstorm while taking the kids to school, you rely on your headlights to lead the way. When your headlights aren’t functioning properly, it not only means that you can’t see but it also means that other drivers can’t see you -- compromising your safety and the safety of your passengers.

If you’re having problems with your headlights, check out this handy troubleshooting guide. Be sure to consult your trusted mechanic for further assistance if you continue to have problems.

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Background info: Halogen headlight bulbs are a popular light source for automotive headlights as they are simple, cost effective, provide a bright light and generally have a useful lifetime of about 1,000 hours under normal conditions. If you drive 12,000 to 15,000 miles per year, you may replace a bulb every 5 or 6 years depending on how much night driving you do.

Solution: Before replacing the bulb in the non-working headlight, check the electrical connector at the back of the headlight for any damage or looseness. The socket that holds the bulb in the headlight housing usually twist-locks into the back of the housing and a quarter-turn counterclockwise will enable you to pull the socket and the bulb out of the housing. Remove the bad bulb from the socket.

Caution: Don’t touch the glass of the new halogen bulb with your fingers. The oil from your skin will react with the special quartz glass and will cause the bulb to heat unevenly, which may result in the bulb burning out prematurely. Handle the bulb by the socket using a cloth or while wearing gloves. After inserting the new bulb in the socket, test the bulb before replacing the socket in the headlight housing by turning on your lights. If the bulb works, replace the socket and you’re on your way.

If the bulb does not light up, the problem could be a corroded socket or a wiring fault, which is a problem best addressed by your mechanic.

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Background info: High Intensity Discharge (HID) headlight bulbs are arc lamps, like a neon sign. Instead of heating a filament to produce light, electricity arcs between two electrodes inside the bulb. HIDs are more efficient than halogen lamps, making more light with less energy. HID headlights require a ballast to step up the voltage, so they also require a more complex electrical circuit with a high-voltage ignitor, which complicates the troubleshooting process just a bit.

Solution: In some HID headlights, the bulb and the ignitor are one unit and both must be replaced. Check your owner’s manual to see if this is the type in your vehicle. If so, take a known good bulb/ignitor and put it in the socket from the burned out headlamp. If the bulb lights up, you know that the original bulb/ignitor is bad and must be replaced.

Other applications of HID headlights use separate bulbs and ignitors, and it’s necessary to do a little more detective work to find out which one should be replaced. Repeat the process outlined above to determine if the bulb is the issue.

If the “good” bulb doesn’t illuminate, you need to take a known “good” ignitor module and connect it with the socket from the burned-out headlight that now has the “good” bulb. If the bulb lights, then you know that all you need to buy is a new ignitor module. If the bulb still doesn’t light up, there is a fault in the wiring harness or a corroded bulb socket and it’s time to call your mechanic for expert assistance. 

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Background info: Driving without headlights is extremely dangerous, reducing your ability to see at night or during inclement weather. If neither of your headlights work it’s time to do some detective work.

Solution: If both headlights aren’t working, it’s unlikely that a bulb is at fault. The likely cause is a fuse, headlight relay, headlight switch, dimmer switch or a wiring fault. About the only cause that is an easy fix is a blown fuse. Consult your owner’s manual to locate the main fuse for the headlight circuit and replace that fuse with one having the same amp rating. If that doesn’t cure the problem, then it’s time to make an appointment with your favorite mechanic for some expert help.

Learn more about quality car lighting, find your car part, or find a local car repair shop today.

The content contained in this article is for entertainment and informational purposes only and should not be used in lieu of seeking professional advice from a certified technician or mechanic. We encourage you to consult with a certified technician or mechanic if you have specific questions or concerns relating to any of the topics covered herein. Under no circumstances will we be liable for any loss or damage caused by your reliance on any content.

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