Car Batteries

Cause Of Lights Dimming In Car And What To Do?

Mike Cross
Updated Oct 18, 2020

So, you are driving your car and all of a sudden the lights start dimming or flicker. You wonder to yourself, what might be causing that to happen? Well, there is a handful of reason why your car lights might be dimming. In this article, we are going to look at all the common reasons that can cause lights dimming in your car. We will cover each one in detail. We will also explain possible solutions to the problem. Read on to learn the main causes for dimming lights in your vehicle.

Cause Of Lights Dimming In Car


So dimming or flickering lights in your car or your headlight  is a somewhat common problem to have. This is especially true depending on the age of the car or the age of certain parts of the car. Flickering lights in your vehicle normally always indicates that there is an electrical problem going on. What exactly the problem is can vary though. A lot of times electrical problems can be hard to find. We will explain the best way though to start trying to figure out what electrical problem there is, so you can start looking in the right area.


Bad battery can make headlight dimming
Bad battery can make headlight dimming

The first electrical component you should think about if your car starts to have dimming lights is your battery. You should think about how old the battery is, and when it was last replaced. An old draining battery could be the cause of your dimming lights. If you have an old battery in your car, then it is a good spot to start when investigating why your lights are dimming.

The best way to investigate your battery is to have it tested. If you or a friend doesn’t have a battery tester, then you can take it to most any shop. At the shop a lot of times they will help test the battery for free.

They are willing to do this because they know that if it is bad you will most likely buy a new one from them, and also come back there for other services. The battery testing can tell you how well the battery is holding a charge, as well as how charged it is getting when full.

Old batteries don’t hold there charge as well and could drain faster then they can recharge while driving, so this is why your lights might flicker or dim. If the battery is not the issue, then you can move onto checking the next thing, which can also be checked while testing the battery. The best battery maintainer is suitable tool for this situation, you can use this tool to recharge your car battery.


The next most common cause of dimming lights in your vehicle, if it has some age to it, is a failing alternator. A lot of times the alternator won’t go out completely but instead will fail intermittently. The period that it is not working is when the lights will dim or flicker while driving. That is because the alternator is what charges the battery and if it stops charging while driving, then the battery will drain.

A lot of times though if the alternator is an issue, then lights will start to come on, on your dash. For most vehicles, if the brake light and the battery light come on at the same time, that means the alternator is going out. Sometimes though these lights will only flicker on, and then go back out because the alternator will start working again. In the daylight that makes it so it might be hard to see the lights. When testing the battery, then can check the alternator and if it isn’t charging right, then the test will tell you. Then you can have it replaced.

Ground Wires

If the battery or the alternator isn’t the problems, then the problem might be in the ground wires. The ground wires are like the name suggest responsible for keeping the car grounded. If the vehicle is old, then the ground wires might have started to come loose. If that is the case, then it could cause the lights to flicker. This is especially a common problem if you notice the lights flickering when you hit a bump.

If you suspect faulty ground wires, then all you have to do is check them. If they are loose, then you can tighten them. They may not be loose though and instead be damaged. Sometimes part of the insulation on the wire might wear off, and the wire grounding out could cause the lights to dim or flicker. If the ground wires are damaged in any way, then you should have them replaced. This should solve the problem you are having dimming or flickering lights.

Voltage Regulator

The last component that might be having issues, if your car is older, and cause the lights to dim or flicker is your voltage regulator. This is a device that works with the alternator to help control the amount of voltage being put out. If too much or too little voltage is being put out, then it could cause your lights to dim or flicker. Normally this part last for a while though, but like anything man-made and mechanical, there is no set breaking point, so it doesn’t hurt to check it if the other things on this list aren’t the issue.

The voltage regulator can be tested at any shop, and a lot of times it can be tested as part of testing the battery. If it is the issue, then you can have it replaced just like you can the alternator.   These four things are the main things to check if your vehicle has some age too it. If your vehicle is not old though, then you need to ask yourself a different question. That is have you installed anything new?

Aftermarket Equipment

If you answer yes to the previous question, then that might just be the reason that your car is having flickering or dimming lights. Installing new aftermarket equipment can easily be the reason your car’s lights are dimming or flickering. That is for a variety of reasons. The first is maybe the part didn’t get installed correctly. If a wire is loose, then it could lead to the problem at hand. Also, if the wires are not connected right, then that would explain the problem. If you have installed something new, then check it to make sure it was installed right.

If the aftermarket equipment was installed right, then you have to move on to the next question. That is can your car’s battery handle the extra load? If the aftermarket equipment is power-hungry, then the alternator and battery you have might not be able to keep up with the draw of the equipment. If that is the case, then flickering lights can occur. Look at the specs of the equipment and see how many draws you are adding. If it is a decent amount, then you might have to upgrade the battery to one with a higher complicity, so you can run all the equipment.


As you can see though from this list, most problems that relate to flickering and dimming lights aren’t major. The bad battery or alternator is the worst because this might lead to your car not starting. That is why it is a good idea to have them checked as soon as your lights start acting funny. The lights dimming or flickering is a good warning sign that you should take seriously so you don’t end up stranded. Sometimes though, it can be hard to figure out the exact cause of electrical issues that is what dimming lights indicate. That is why it is key to ask yourself is your car old or did you install something new, so you can start looking for the possible problem in the right order.

Mike Cross
Life is too short to drive with stock audio

Leave a Reply

Your email address will not be published. Required fields are marked *

linkedin facebook pinterest youtube rss twitter instagram facebook-blank rss-blank linkedin-blank pinterest youtube twitter instagram