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How to Fix Car Light Dimming and Brightening

March 3, 2024 | Victor Lukasso

Car lights are helpful in navigation, indicators, and visual inspection of objects while driving. What should you do if your car lights start Dimming and Brightening?

Dim car lights are often encountered when you hit the brake, slow down, idle the engine, or speed up your vehicle. Whatever the case for your car, it’s necessary to know the causes and how to fix a Dimming and Brightening Car Light.

Failure to fix a Dimming car Light will likely get you in trouble with the law, endanger other road users or cause you to do things your car lights manually are supposed to do – highly risky.

Some of the fixes to a Dimming and Brightening Car light(s) are to get a bulb replacement or check the wiring harness of the light system.


In essence, faulty car lights should be addressed almost immediately, especially if you mostly hit the road at night; it also enhances your driving experience by making navigation and passing information to other drivers easier.

Without wasting much time, let’s look at some possible causes of Dimming and Brightening Car light(s) and possible solutions.

Car Lights Dimming and Brightening – Causes

Some of the primary reasons your stable car light will start malfunctioning are listed and explained below.

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1. Faulty Bulb

Since the bulb is the main suspect, it’s expedient to visually inspect the bulbs on the Headlights, fog lights, and frontal lights once the light starts blinking.

If you notice that one bulb illuminates brighter than another, it could be that the bulb in question is weak and needs replacement. Since all auto parts have a lifespan, they could be due for replacement or worn out due to excessive usage.

2. Problem with the Wiring

A problem in the wiring harness of the bulb system will result in it giving out low lights.

This includes poor connections, worn-out wires, short-circuiting, or a faulty electrical system.

Sometimes, a bad battery or alternator also gives off these signs, so monitor each of your car components well.

3. Damaged Headlights

Excess exposure to sunlight will cause yellow deposits in your headlight coupled with the dust and dust particles that speed up the discoloration o the bulb or headlights.

4. Dirty lights

Also, if your bulbs are in constant contact with dirt or sunlight, they could get into the bulb(s) and cause the light to give off lower light.

5. Mechanical Faults

Mechanical Faults, such as damage in the light chamber or lens, can affect the illumination power of a bulb.

How to Fix Car Lights Dimming and Brightening Issues

A Dimming and Brightening Car light should be fixed if one or more of the below DIY guides are implemented.

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1. Get a Bulb Replacement

A bulb replacement is the first thing that should come to a car owner’s mind, but it’s also necessary to troubleshoot the bulb(s).

You can connect it to another source and see if the brightness is still the same. Also, check for dirt accumulation or if there’s a break.

In addition, it’s necessary to go for high-quality bulbs that fit perfectly on our car with a longer lifespan.

2. Check the car Battery and Alternator

A low power supply from the battery could result in a Dimming and Brightening Car light.

It would be best to consider checking the battery and alternator for green matters. You can also jump-start the car battery using a jump starter or get a new battery at most.

In the case of an alternator, you can check out the alternator belt and get a new one if necessary.

3. Check the Wiring Harness

Faults in the wiring will cause the bulb to illuminate less or lead to fluctuation in light emission. A visual inspection of the bulb connection should give you a clue on open connections that needs to be taped or damaged wires that need replacement.

4. Cleaning the Headlights

To enhance road visibility, you should regularly clean the outside casing of the headlight using a moist cloth. If the stain remains stubborn, you can loosen the headlight using toothpaste and sandpaper for the cleaning procedure.

5. Replace the Light Assembly

If the stain remains stubborn after applying the above steps, it’s high time you get a new light assembly. You can check for the correct replacement light assembly from Amazon or any auto repair shop nearby.

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A standard light assembly headlight for your car will cost between $90 to $2,000, depending on the model of your vehicle.


Q: Why Do My Lights Get Brighter When I Speed Up?

If your headlights become brighter as you speed up, then there is a fault with your alternator voltage regular. It functions as a regulator that balances power outflow and prevents a sudden increase in brightness when the alternator speed increases.

Q: Why do my car lights Dim While Driving?

If your car light suddenly becomes dim while driving, it indicates that your battery is either low, faulty, or has an issue with your alternator. The best way to get rid of this is by using good car batteries and ensuring other electrical components are put in place.

Also, the car light will dim whenever you’re revving the engine due to the power being dissipated.


Clear visibility is necessary to achieve an enjoyable driving experience, and the headlights play an essential role in making sure tracks are visible to drivers at night; drivers can use the light to relay information to other drivers, etc.

But what happens when the headlights become dim and lose their brightness? This could reduce road visibility, which would result in accidents.

Factors that also enhance the dimming and brightening of bulbs include frequent contact with dust and foreign matters, sun rays, and the lousy wire connection, amongst others.

However, you can follow the article to eliminate the dimming and brightening of headlights on your vehicle or that of a friend.

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Meet Victor Lukasso, the owner of V. Auto Basics. Through this blog, Victor Provides Insights on the latest tips, maintenance, repair, and techniques in the automotive world.