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6 Common Causes and Solutions for Flickering Headlights

February 21, 2024
Flickering Headlights

Table of contents

Fixing flickering headlights could be as simple as tightening a few loose wires or as complicated as having to repair your alternator. In this article, we take you through six common causes of flickering and their solutions. 

1. Dying Batteries

Flickering headlights can be a sign that your battery is nearing the end of its life or needs to be recharged.


A good quality car battery is expected to serve you for 3 to 5 years. As the battery approaches the end of its life, it will not be able to hold a charge. In this state, your car’s alternator won’t be able to charge it properly, and the battery won’t stay charged for long.

Car battery with jumper cables attached.

The battery is an important part of your vehicle’s electrical system. Its main purpose is to start the car but it’s also recharged by the alternator which powers other electrical components. A dying battery forces the alternator to work harder and this can affect other components including the car headlights.


If your car battery is dying, the best solution is always to replace it. Recharging a failing battery is only a temporary fix as it won’t be able to hold the charge for long. 

If you have a voltmeter and are familiar with working under the hood of your car, you can test the battery yourself. However, working around batteries is risky and this job can be easily done by a qualified technician when you go for an oil change. 

2. Faulty Alternator

A faulty alternator can cause flickering headlights and many other electrical issues in your car.


Alternators are the heart of your car’s electrical system. It converts mechanical energy into electrical energy that is used to charge your battery and power the electrical components when the engine is running. This includes the car’s headlights.

Close up of alternator inside car

Alternators can be rendered faulty by many issues including corrosion, bearing damage, water or oil ingress, a short circuit, etc. If your battery is relatively new or has been confirmed to still hold a charge well, your alternator might be the reason behind your flickering headlights.

Other signs that you may be dealing with a faulty alternator are:

  • Difficulty starting your car with a fully-charged battery
  • Slow power windows
  • Overheating engine
  • Burning smell from under the hood
  • Very bright headlights
  • The battery light on the dashboard will be on.


Unlike batteries, alternators can be repaired if the damage is not severe. Repairing or replacing a faulty alternator is a very technical job and is best handled by a certified professional. A poor repair job or poor installation of your alternator could result in serious damage to the electrical system and battery. 

Alternators have different components that have to be individually assessed such as the voltage regulator. It could be just one of these components that needs to be changed and not the whole alternator. 

3. Faulty Bulbs or Bulb Connections

A faulty headlight bulb may flicker. The headlight flickering could also be due to a poor connection in the bulb socket. Fortunately, these are easy issues to resolve.


When bulbs fail or are close to failing, you may see signs such as dimming or flickering before the light bulb goes out completely. 

Halogen headlights may flicker because of a broken filament that is still attached to an electrode. LED headlights can flicker because of a damaged driver or because of incorrect input voltage. A damaged ballast could also cause the flickering of HID lights.

You may also notice headlights flickering if you have damaged or corroded bulb sockets. Corrosion in the socket makes it difficult for headlight bulbs to get a clean connection to the terminals.


When you’re dealing with a faulty bulb the solution will often be to replace it. Repairing a faulty bulb is more trouble than it’s worth, assuming it’s even possible. 

If the bulb was damaged due to a problem with your vehicle’s electrical system, it’s wise to have the system checked out otherwise you may need to replace your new bulbs again. 

If the issue is a corroded bulb socket, cleaning out the rust or replacing the socket should do the trick. You should also check that the headlight is properly sealed since corrosion is a common sign of moisture ingress.

4. Loose or Corroded Wiring Connections

Loose or corroded wiring can cause flickering but the real challenge might be finding the affected wires.


When your headlight wiring has a loose or broken section, vibrations can cause intermittent breaks in connection. This will result in your car headlights flickering especially when driving over rough roads.

Close up of car revealing wires.

Corroded terminals can also cause a similar issue because the connection is not clean. The corroded parts separate the surfaces that conduct electricity making it harder for the clean surfaces to come into contact. A loose headlight fuse will have a similar effect on your headlights.


The main challenge when dealing with bad wiring is locating the loose connection behind the problem. Your headlight’s wiring harness will have to be diligently inspected to identify the loose or corroded connection. 

In case a wire is broken internally, visual inspection won’t be enough. You’ll need a few tools to identify such a problem. Once the connection has been identified, it can be cleaned, tightened, or replaced to stop the flickering.

5. Grounding Issues

Still on wiring issues, a flickering headlight can also be caused by a loose ground connection.


All electrical components in your car need to be grounded to the chassis. Grounding is necessary to complete the circuit for any component that receives a current from the positive terminal including the headlights and engine.

Ground wires are easy to miss but any damaged or loose grounding wires will cause electrical issues. These connections can become loose or corroded, or they can be broken. If a headlight’s ground wire is affected the electric circuit may break intermittently resulting in flickering.


As with the previous wiring issues, the main challenge will be tracing the offending connection. Each headlight should have a separate grounding wire, but tracing these wires requires an expert. 

If a loose, broken, or corroded connection is found, it can be tightened, cleaned, or replaced easily. Many auto mechanics will look for grounding issues before checking for a failing alternator because it’s one of the most common causes of flickering headlights. 

6. Dimmer Switch Problems

The headlight switch is part of the circuit that powers your headlights. If you have a faulty headlamp switch, it can cause flickering.


Electrical switches work by making or breaking a connection in the circuit. This turns the lights on and off. However, some components of the switch can become worn and loose.

This will have a similar effect to the loose connections where the circuit is intermittently connected and disconnected. The result is also the same, i.e., flickering headlights.


The best solution for a failing headlamp switch is replacement. The main challenge is establishing that it’s the switch and not another component that is causing the flickering. 

Another challenge is that replacing the switch will require accessing and working on the electrical system in your car. Working on automotive electrical systems can be dangerous and can result in damage or injury.

Car with LED headlights on

A professional will have an easier time identifying and fixing this kind of problem. 


Many issues can cause headlights to flicker, but some sort of loose connection is usually the culprit. In extreme cases, it may be an indicator of a problem with your alternator, battery, or headlight switch. 

Halogen, HID, and LED headlights can all be affected by this problem. If you suspect the cause is something that requires working on the vehicle’s electrical systems, it’s a good idea to let a professional handle it. 

Why Rely On Carlightvision for LED Headlight Expertise?

At Carlightvision we have extensive experience troubleshooting issues that affect vehicle headlights. Installing LED headlights can solve a lot of problems on the road, but these lights are not immune to all the problems that affect traditional headlights. Reach out to our experts today to find out how we design and manufacture our LED bulbs to avoid common headlight issues.


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Hey there, I'm Mark Yang, Hope my blog posts can help you. I have been in the car light field for more than 20 years. So if you have any questions, I'm always happy to help you.
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