How Do I Stop My Lights From Flickering When Bass Hits?




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Having a killer sound system with incredible bass in your car is the envy of many car audio enthusiasts. However, many are plagued with dimming headlights when they crank up that lovely bass.

This problem is more frequent than you would think, so let’s find out how to keep lights from dimming when the bass hits.

As a general rule, to keep your lights from dimming when the bass hits, you will need to make sure your alternator and battery are in perfect condition. Other solutions to consider are installing a power capacitor and replacing your headlights with LED headlights.

Tip: If you are struggling with dimming lights due to heavy subwoofers that draw lots of power and don’t want to turn down the volume, you need to consider adding the capacitor with an absolute minimum of 1F per amplifier’s 1,000W RMS.

My best pick is the SoundBox SCAP2D, which with 2.5F is enough for the amplifiers up to 2,000W RMS.

If you have a powerful amp, use stronger BOSS Audio Systems CAP8, which will stabilize sound systems with up to 6,000W RMS, and for a system over 10,000W RMS, I would use Power Acoustik PCX-30F, the 30 Farad monster.

In this article, I will cover everything you should know about why this problem persists and how to solve it once and for all, giving you the simplest fixes you may want to consider.

What Causes My Lights to Dim in Car?

The main reason your headlights are dimming when your bass hits are because the amplifier is drawing a large and sudden amount of current when bass notes are being played at high volume.

If your car’s electrical system (this includes alternator) can’t match the power required from the subwoofer’s amplifier, the voltage in your vehicle will suddenly drop. This is the reason your headlights are dimming every time the bass kicks hard.

How Do I Check if the Voltage Is Dropping in My Car?

Your dimming lights are a clear indication that the voltage is dropping. However, if you want to get a bit more technical, for example, when installing the capacitor, you may want to check the voltage by performing a voltage drop test.

Voltage drop is a mechanical test that uses a Multimeter and measures voltage drop across a load device or conductor.

The test you have to make in the areas where the voltage is dropping, so in our case, you would test the current that the lights are drawing.

Why Do My Lights Dim Even With Capacitor?

A couple of factors could play a role in this situation, and some of them are not as easily recognizable as you may think.

You Did Not Use the Correct Size Capacitor

The first one is that you have installed a capacitor that does not meet the requirements of your car speakers. Many people think they will only need to get any capacitor and job done. Well, this is not entirely correct.

You will need to get a strong enough capacitor to hold the total amount of your car audio system’s power. Typically, the absolute minimum is the 1 Farad of capacitance for every 1,000 watts RMS.

In multi amp systems, this value should increase to close 2F for every 1,000W RMS. Remember that capacitor won’t work correctly if it is not strong enough.

Capacitor Is Not Close Enough to the Amplifier

Another reason that your lights are still dimming when you have installed a capacitor is that you have placed it far away from your car amplifier.

It should always be mounted as close to the amplifier as possible using the shortest wires were possible. It needs to be close to the amp, so the current does not have a far distance to travel.

You Did Not Use the Correct Wire Gauge for Your Capacitor

Wire gauge is also critical when it comes to how current balances out the resistance.

Thin wires offer more resistance than thicker wires because fewer electrons can carry the current down the conductor (wire).

As you know, the capacitor needs to have short wires that are placed close to the amp. Ensure that the cables have a sufficient gauge following the power that is being sent to your amplifier. 

Capacitor Was Not Charged Correctly

There are some cases that you may have installed your capacitor close to the amp and used the correct gauge wire, but it is still not working.

This could be because you did not charge the capacitor before installing it into your system.

You should know that a capacitor can be very dangerous, so they are always sold completely discharged. Typically, a set will include a resistor in your capacitor package so you can discharge it safely, and sometimes they can even come with a wired or a LED light.

This resistor or lightbulb is also used to charge up the capacitor. Meaning you can’t just connect your capacitor with the audio system and think it should work.

In most instances, a capacitor should come with a manual, and It only takes about a second to charge the capacitor when you connect it to your electrical system.

If it is not charged correctly, it will not function the way it’s supposed to, and it could even cause sparks or melt itself.

A Capacitor Is Damaged

In some cases, your capacitor could be faulty, meaning it is not sending the correct amount of current to your amplifier.

This does not happen often but, it can still occur. Again, you would need to test this with a Multimeter if you can, otherwise take it back to the dealer and let them try it for you because again, capacitors are very dangerous.

Are Dimming Lights in Car Dangerous?

Although nothing will happen with incandescent headlights if they keep dimming while your bass is playing, there are concerns for the safety of road users and yourself when on the road at night or in bad weather.

Dimming headlights in bad weather or at night means you won’t see the road correctly. Remember, you are typically using your headlights in the dark, so not seeing the road properly is a sure way to get into an accident.

Another factor to consider is that other motorists may think you are “flashing” them with your headlights. 

Having another motorist think that you are “flashing” them could cause unforeseen problems on the road and should be avoided at all costs. Remember this again; it will more likely than not increase your chances of you having an accident.  

How Do You Fix Dimming Headlights?

Check Your Electrical System Before Anything Else

The first thing that should be on your list before you consider any other options is checking your vehicle’s electrical system.

The most common scenario that most people find is that their alternator is too weak and can’t keep up with the demands of the electrical system (amplifier).

You should have your alternator and your battery checked by a qualified technician. You can check the voltage of your battery pretty quickly using a Multimeter, but you may need to ask a professional to inspect your alternator.

A standard car battery, when in good condition, should read between 12.4 and 12.9 volts when the car is turned off. However, when the vehicle is running, it will be getting a charge from the alternator. Thus the reading on the Multimeter will be between 13.8 and 14.5 volts.

If your battery is not reading within these voltage ranges, then it may be faulty, and you may need to replace it.

Although there are literally thousands of different batteries on the market, I personally like Optima red for a start-up engine or yellow if I want to add an amplifier to the car audio.

I never had a problem with the Optima batteries, and if you would like to give them a try, click the above link and check the latest price. Before ordering, make sure to check if a specific battery will fit in your car.  

If your electrical system is the problem, you should sort this out first. What’s great is that you may find that some auto repair shops will even test your electrical system for free. You may even want to consider purchasing a larger alternator and getting it installed by a professional.

Your alternator supplies power in the form of amperage. What is remarkable is that the alternator will only supply the correct amperage for any component in your vehicle and no more.

This means that high-output (larger) alternators will not damage your car’s features or its charging system in any way.

Install a Power Capacitor

After you have checked the electrical system and it is fine, and you are not opting to install a larger alternator, the next thing you could do is install a power capacitor.

As I already mentioned earlier in the article, my favorite capacitor is SoundBox SCAP2D. It has a capacity of 2.5F, which is enough for amplifiers up to 2,000W RMS.

A capacitor will help to smooth out peaks in the current draw from your amp. After installing a capacitor, you will definitely tell the difference when it comes to peaks in the music, such as when the bass is loud, or the kick is prominent.

A capacitor stores charge and will supply your amplifier with the current it needs without going to the battery, which it will typically do.

Besides ensuring that your lights don’t go dim, it will also help ensure that the music does not drop in volume when the amplifier draws lots of power.

However, there are a couple of factors you will need to consider before doing this.

The first is the size of the capacitor. You will need to get one that is large enough to suit your stereo system. Remember that capacitors come in various sizes, and every car audio system will draw different amounts of power.

One Farad per every 1000 watts RMS of your total audio system’s power is the absolute recommended minimum to get the job done.

Take into consideration that if you choose to get a larger capacitor, this will not hinder your system in any way. In fact, you may see added benefits using a capacitor that is 2 or even 3 Farads per 1000 watts.

This is because using a larger capacitor means it can store more power, and thus, more charge is available to the amplifier when those bass notes are pumping.

The next thing to consider is how close to the amplifier you need to install the capacitor. The closer you install the capacitor to the amplifier, the better off you will be.

Remember that it takes time for the current to run along a conductor. So the further away your capacitor is from your amplifier, there is a probability, in that split second, when you need “extra juice” from it, it won’t send the charge quick enough to the amplifier.

Change Your Headlights From Incandescent Bulbs to LED

Technology has come a long way regarding all aspects of our daily life, and this includes being able to get LED headlights for your vehicle now. You may be wondering why you should replace your old headlights with LED ones?

Incandescent lights use a filament that is inside the glass bulb. When the electricity heats up this filament, it produces light. The downside is that incandescent bulbs require a significant amount of power for them to shine brightly.

On the other hand, LED lights send an electric current through semiconducting material known as the diode. This diode emits photons (light) through the process of electroluminescence.

These types of lights require much less energy for them to shine just as bright (if not brighter) than incandescent lights.

In fact, incandescent lights use almost twice as much energy as LED lights when considered in a scenario using car headlights. Check out this short video to see that incandescent lights read almost 5 amps when running compared to 2.10 amps with LED lights.

Not only that, but they test incandescent lights again LEDs with massive bass to see if they will help solve the problem of dimming lights.

Due to your incandescent lights drawing so many amps from the alternator, they will likely dim when voltage drops. Installing LED lights could solve your problem if you have tried all the other remedies we have given you. 

If you decide to replace your standard bulbs with LED lights, check this broad selection on Amazon. To ensure they will fit in your vehicle, you have to put the production year, make, and model to see the results within seconds.

Can I Add a Secondary Battery to My Car Audio System?

Many think that adding a secondary battery to the audio system will fix the dimming lights issue, but that is a terrible idea.

The main component in a car that keeps the battery charged is your alternator. It is also responsible for supplying power to the electrical system while the car engine is running.

If you go ahead and add another battery to your current electrical system, it will store more power, but it will subsequently also add much more load to the alternator.

When the alternator is overloaded, it will drop its voltage, and the battery charging process will be reduced. Nothing will happen to the alternator, but you could have instances where a 100-watt bulb will shine like a 10-watt bulb.

So, if you have a problem with lights flickering due to heavy bass, adding a second battery will not solve the problem.


Now you know that there is a voltage drop when your bass is playing at loud volumes, which causes your headlights to dim.

Your amplifier in those instances where the bass is sucking a lot of power drops the voltage because your alternator is not strong enough to handle the capacity of your amplifier.

Although dimming lights can not really damage your car’s electrical system, they will be a hazard on the road and could cause you to have an accident, so you should take care of them immediately.

To do that, you first need to check your electrical system, and if necessary, replace your battery or alternator. If this were not the problem, you might need to install a power capacitor or changing your incandescent headlights to LED headlights.

This is because LED lights draw much less power than incandescent ones. By now, you should be armed with the knowledge to go out and fix your car audio system, specifically, the problem of your dimming lights.

Source list

Headlights Dimming

Car Lights Dimming and Brightening: Causes and How to Fix It


What’s a capacitor? What they do and when to use one

How Do a Car’s Headlights Work?

How an LED Light Bulb Works