You’ve just left your driveway or pulled into a parking space and notice that one headlight or both may be flickering abnormally. This is a problem that can lead to a world of hurt, especially if most of your commute is done during the early morning or nighttime hours. If you wish to learn how to diagnose your flickering headlights issue, here’s what to look for when figuring out what to replace or repair.

Bad alternator or battery

If you notice that your car’s headlights flicker upon starting the ignition, you may have a bad alternator or battery that needs replacing. You can test these at your local auto repair shop, or you can do it on your own if you have a handheld multimeter system that can measure voltage and a battery testing/charging system that can tell if your car battery is on it’s way out. 

If the meter reads below 10 volts after you start your engine, you should replace the alternator because it should read between 13.8 and 14.2 volts. If this checks out, test your car’s battery and switch it out with a new one if it’s expired. If all tests for the battery and alternator go well, here’s what’s next on the list.

Blown fuse

The first thing drivers should check for is the fuse. It’s wise to check the simple and easy-to-reach components first, because the issue may be a quick tightening of a loose fuse or a fuse replacement. 

Check your car manual if unaware of where your vehicle’s fuse compartment is, then read the fuse card (which is usually attached to the compartment hood) to find the fuse for your headlights or tail lights. Once you find the designated fuse, view it to see if the metal between the plastic is broken or separated. If there is a break, you will need to replace it with the correct fuse number. Car fuses can be bought online, or at your local auto parts store.

Broken headlight bulb

If the fuse is intact, then pop the hood and begin analyzing your headlight bulbs. If a bulb has burnt out, it may have a black or faded spot where the filament of the bulb has burst. This may be caused by an imbalance of the wattage in the bulb and car harnessing or faultiness in the bulb or common wear and tear. 

Some bulbs may appear normal on the outside, but there could possibly be corrosion on the bulb socket. Take the bulbs out and inspect them inside and out. If you notice that grime and dirt build-up has gunked up your bulb sockets, clean the socket with a cloth or soft-wire brush, or replace the bulb altogether.

Faulty or damaged headlight harnessing

If the socket harnessing seems melted or the tape wrapped around the wires is old and gruesome, consider replacing the harnessing connection. The bulbs may be fine, but the issue could be from a short circuit in the cable or junky socket connectors. In this case, you can order specifically-sized harnessing cables for your car’s year, make, and model online. 

Broken headlight switch

It may be something as simple as a broken headlight switch. Faulty parts sometimes make it past a car’s factory inspection and replacement switches are affordable. If you notice a delay in the lights when turning them on at night, or the nighttime headlight sensor is failing to kick on, it’s smart to take it to your local dealer or auto repair shop, because it may require professional mechanical attention.

Replacing headlight bulbs and components

If you’re looking to do a total rehaul of your car’s lighting system, this would be the perfect time to switch from your old halogen headlights to something newer and brighter, like LED or HID bulbs. This type of installation would require new harnessing cables anyway, and for a little extra money, you can install new bulbs and add a fresh new look to your ride while also optimizing your visibility when traveling through the night.

Flickering or rapid turn signal issues

Another common vehicle light issue is a rogue turn signal. You may notice a speedy clicking or rapid flashing of your front or tail turn signal and this is a warning sign that the bulb will soon burn out. Turn signals are more than necessary for traveling the roads and highways and without proper functionality, you may cause an accident or receive a traffic citation. 

A turn signal bulb fix is simple. Once you purchase a new turn signal bulb, find your way into your car or truck’s headlight or tail light housing, and simply twist the old bulb out and install the new one.

Accessories for replacing your headlights

If you’re uncertain about replacing your headlights, we understand it can be a complex decision to make. After you conduct your headlight and bulb inspection, browse a list of online LED headlight bulbs or replacement halogen headlights to find what fits your budget and car’s style best.

With a few simple tools and time, you can knock out a headlight bulb replacement in less than an hour or two.

Patrick Kirk
I am a full-time copywriter from Naples, FL and living in Austin, TX. I have written for the automotive industry for three years, and enjoy other hobbies such as camping and mountain biking. I received my Bachelors from Florida Gulf Coast University, and served in the U.S Coast Guard.

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    8 Comments

    1. This was super interesting. I am a do it yourself kind of woman and love learning how to troubleshoot things on my own. You would never think that many components go into the bulbs. I would have just thought to check the bulbs itself. You learn something new every day.

    2. Every automotive enthusiast should own a volt meter, and spare fuses. You will be surprised how many issues are resolved by testing with a volt meter.

    3. This was a super informative article. Unfortunately, some cars don’t allow for easy bulb replacement, requiring the disassembly of the entire front of the car, while others are simple plug-in.

    4. Always wondered what this was now I know!

    5. This is very informative, doing simple checks on your own is actually a fantastic way to save a lot of money on repair bills and for the most part the solution is easy enough for you to do yourself and skip the repair shop all together.

    6. What I noticed first was the part about the car battery or alternator. Maybe it was fate that this article was posted!

    7. Some LED bulbs can cause flickering and may require an anti-flicker module to remedy the issue.

    8. Great article, but when your turn signal is blinking fast, it doesn’t mean it will go out soon, it means its already out. Replace ASAP to avoid getting pulled over.

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