6 Possible Causes For Headlight Flickering



You may look past some minor car issues, but there are some you cannot– like flickering headlights. Not only is a flickering headlight bothersome, but it could also cause bigger problems if ignored.

A flickering headlight can die at any time, as its cause can be connection problems. This issue can put you in a precarious situation, especially on the road. A flickering headlight can signal problems with your battery or alternator. When left unresolved, it can cause further issues with your main power or devices.

Read on to know the causes of a flickering headlight that you must promptly address.

What Causes Flickering Headlights?

A flickering headlight is one problem, but its causes can have several origins. Warning lights can accompany flickering headlamps if there’s an issue with the electrical system. But, sometimes, the issue needs a deeper diagnosis.

You must remember six of the most common causes of flickering headlights. These causes may have different degrees of urgency, but you must resolve them appropriately.

1. Dying Battery

Your car’s battery is directly responsible for your headlights’ performance. After all, it is the power source your headlamps rely on.

A car battery can fail earlier than the average life span of 3-4 years. It can deplete faster if you run aftermarket accessories like speakers and LEDs. You’ll also strain your battery faster if you constantly drive in extreme heat or cold. Not only is air-conditioning power-hungry, but cold starts also severely stress the battery.

When you see your headlights flicker, the first thing to do is check your battery. If your battery is far from its expected replacement date, it may not be the culprit. But if your dashboard lights flicker along the headlamps, it’s likely a dying battery.

To be sure, you can check your car battery life with a voltmeter. Connect the device’s positive and negative terminals to the battery. With the car turned off, your voltmeter should register a reading of 12.4V to 12.7V.

2. Failing Alternator

Do you have a new battery, but your headlights still flicker? The car alternator could be the culprit.

Every time your car runs, the alternator converts mechanical movement to electrical energy. This energy conversion charges your car battery so as not to deplete it. When the alternator starts failing, it no longer appropriately recharges the battery.

Your battery will deplete faster, leaving you with dimmer lights and an illuminated battery warning light. It is best to fix or replace your alternator to avoid fully draining your battery. If you leave the alternator bad, the battery can quickly drain completely.

Even your new battery stands no chance, especially if your electrical devices run simultaneously. So, when your headlights flicker despite a new battery, pop the hood and check your alternator.

3. Failing Bulbs or Lamps

A drained battery isn’t always to blame for flickering headlights. Sometimes, the bulbs of your headlamps fail earlier than other components. Worn-out or damaged bulbs flicker to sign an impending end to their service.

This issue is good news as it often doesn’t come with hidden problems. You can simply bring your car in for bulb replacement, and the flickering will disappear. You can do it yourself, which wouldn’t even last an hour.

4. Faulty wiring

Loose wiring is also a potential cause of headlight flickering. A classic example is a loose connection on either end of the terminal.

Worn-out wires lead to connections hanging by a copper thread, literally. However, lousy work can also lead to faulty wiring. If you or your mechanic fastens a terminal loose, your lights could flicker due to poor connection.

Either of the two will result in reduced conductance and increased resistance. A flickering light may persist when connections do not allow optimal current flow.

5. Loose Connection or Fuses

Have you been on a bumpy ride and come home to a headlight turning on and off? This can be a case of a loose connection or fuse.

Your vehicle’s electrical system involves complex wirings and fuses that can knock loose. There’s a dedicated fuse for the headlamps, and it can unfasten sometimes. A loose fuse can be hard to detect, so it’s best to consult a mechanic if you can’t determine the origin of a flashing headlamp after several tries.

Other loose connections result from corrosion or oxidation around terminals. Corroded terminals will produce increased resistance, causing the light to flicker.

6. Faulty Headlamp Switch or Circuit Problem

The headlamp switch is also vulnerable to breaking down. The constant turning on and off of the switch wears the component over time. You can observe it when the flickering results from slight movements or vibrations to the switch.

Sometimes, a bumpy ride can trigger the switch to go off. Or when you touch it slightly, the light goes off or on. This is a clear sign of a loose switch. This symptom calls for a switch fixing or replacement.

A headlamp circuit problem is also possible to cause the flickering. Such issue often ensues due to loose wiring within the circuit. But if you drive an older car, it can be an issue with the circuit breaker.

Older cars have a circuit breaker that is triggered when there’s a short circuit. This causes the affected headlamp to turn on and off continually. Usually, this only happens in one headlamp, but if two headlamps flicker at the same time, it could mean total failure of the circuit breaker. This means the worn-out breaker can no longer handle the amperage and needs replacement.


Q1: What should I do if my headlights are flashing?

Refrain from driving, especially at night, once your headlights are flashing. You must visually inspect the physical connections that may be causing the issue. Or run diagnostic tests on your battery and wirings.

You can run voltage testing on these components to pinpoint the causes of your light problem. Or bring your car to a certified mechanic to look at it and avoid missing out on issues you can’t detect.

Q2: Why is only one headlight flashing?

Uneven contact in the switch or relay can cause only one headlight to flicker. But it’s also possible that such a headlight has a faulty bulb or connection.

Newer cars have separate fuses for each headlamp filament. If a fuse is loose, there’s a slight chance that the filament it supports will flicker separately. You can bring your car for a professional inspection if you suspect this. As noted, it is tricky to detect which fuse has the problem, so letting certified mechanics handle the work is your best option.

Q3: How can I tell if my alternator is causing the headlights to flash?

If your headlights flicker even with a new battery, you know you have an alternator problem. Your alternator is supposed to recharge your car battery every time you drive. If it fails, your battery will be drained, leading to light problems.

But even with an old battery, you can still point to an alternator problem. Besides dimming interior lights, you can also hear strange noises from the alternator once it goes bad. So, it’s likely an alternator problem if these signs go with your flickering lights.

Q4: Is it safe to continue driving with a flashing headlight?

A flickering light may sound trivial, but it’s a dangerous thing to drive on. Several problems, including loose connections, can cause a flashing headlight. This means your headlamps can die at any time, even while you’re on the road at night, thereby exposing you to an accident.

Besides the safety concern, you also risk your car’s other electrical systems failing. A flashing headlight can signal a drained battery or failed alternator. If these issues continue, they can cause further problems. So, it is advisable to always refrain from driving with flickering lights and check for problems under the hood.

Q5: What measures can I take to prevent flashing headlights?

The issue of flickering headlights is mainly about the car’s electrical system. You must observe regular maintenance of all the electrical systems, as failure from one system could affect others.

Avoid conditions that could strain your battery as much as possible. Maintaining your battery’s optimal health prevents electrical malfunctions. So, proper battery maintenance also equals maintenance of your overall electrical systems.

Replacing your headlight components when they’re due is also a big step to avoid related problems. While longevity of components is a good thing, timely replacement is better as a maintenance measure.