How to Fix Car Light Dimming and Brightening

Car lights are useful in navigation, indicators, and visual inspection of objects while driving. What then 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 may be for your car, it’s necessary to know the necessary 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 manually do things that your car lights 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 take a look a look at some of the possible causes of Dimming and Brightening Car light(s) and possible ways to fix the problem.

Car Lights Dimming and Brightening – Causes

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

1. Faulty Bulb

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

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

At times, a bad battery or alternator also gives off these signs; so do well to monitor each of your car components.

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 then it 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.

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 do this by connecting it to another source and seeing if the brightness is still the same. Also, check for dirt accumulation or if there’s a break.

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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.

You should consider checking the battery and alternator for green matters on it. 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 also get a new alternator 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, it’s advisable that you regularly clean the outside casing of the headlight using a moist cloth. If the stain remains stubborn then you can loosen the headlight to use toothpaste and sandpaper for the cleaning procedure.

5. Replace the Light Assembly

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

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


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 keeps power outflow balanced and prevents a sudden increase in brightness when the alternator speed increases.

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Q: Why do my car lights Dim While Driving?

If your car light suddenly becomes dim while driving then it’s a clear indication that your battery is either low, faulty or there’s an issue with your alternator. The best way to get rid of this is by making use of good car batteries, and making sure 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 important role in making sure tracks are visible to drivers at night, driver can use the light to relay information to other drivers, etc.

But what happens when the headlights start becoming dim and start losing 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 bad wire connection amongst others.

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

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