Dim Head Lights: What Are the Causes and Solutions?

Dim head lights can creep up on anyone without warning, which can be annoying. It is even more frustrating when your headlight cannot cover the distance it used to when you travel at night. The worst part is when you don’t even know the root cause of the problem or how to solve it.

Dim Head Lights

Fortunately, this article will discuss the possible causes of dull headlights and how to solve them, so continue reading!

What Are the Most Common Causes of Dim Headlights?

The most common causes of dim car headlights are aging, the bulb could be discolored, or the voltage might be low. A corroded ground wire, a faulty alternator, a broken alternator belt, and a dying bulb are other possible contributing factors.

– Discoloration of Old Headlight Lenses

The headlight lenses of cars are protected by plastic, which ages with time. As they age, the plastic covering becomes yellow due to the harsh ultraviolet rays from the sun. This yellowish color restricts the passage of light; hence the headlights appear dim.

Other items, such as rocks and debris, can scratch the surface of the glass, making it cloudy. This reduces the distance the light covered when it was new.

– Discolored Halogen Bulbs Forming a Thin Film

Modern headlights have halogen bulbs that can become discolored over time. This happens when the halogen bulbs in the headlights form a thin film inside the glass. This thin film prevents the full force of the light from escaping, making the light dim. Hence, visibility becomes poor at night, endangering the lives of both drivers and pedestrians.

– A Damaged Alternator Not Producing Enough Power

Another reason your car headlights dim is a damaged alternator. The alternator converts chemical energy to electrical energy to restore the energy discharged by the car battery. It also provides energy to other electrical components of the vehicle, including the headlights. Thus, if the alternator becomes damaged, it won’t produce enough power to keep the headlights bright.

Common Causes of Dim Headlights

This puts extra pressure on the battery, which will fail because it wasn’t designed to shoulder such extra responsibilities. This is why your headlights will lose their brightness and eventually go out, leaving you stranded on the way.

– A Damaged Belt Not Powering the Alternator

When your headlights brighten and dim intermittently, your alternator belt may be worn out. The belt connects to a pulley that spins to produce electricity for the vehicle’s electrical components, including the headlights. A damaged belt will alternate between gripping the pulley and slipping off it. This gripping and slipping will make headlights dim and brighten while driving.

The belt will lose its grip when left unattended, resulting in permanent low light. Note that the alternator belt is usually stretched; thus, it’s common for it to undergo wear. This answers the question, “Why are my projector headlights so dim?” We’ll come to the solutions later in this article.

– A Corroded Ground Wire Not Transmitting Enough Energy

The grounding wire connects the battery to your car’s chassis and completes the electrical circuit. It ensures a constant flow of electricity throughout the vehicle and enough to power the headlights. Therefore, if the ground wire is corroded, it can’t transmit enough current to the headlights, causing them to shine less brightly. Eventually, the corrosion will spread and completely cut out the electricity supply to the headlights, forcing them to go out.

– A Bulb Nearing the End of Its Life

Like any other car component, a bulb will dim and flicker as it nears the end of its cycle. Halogen bulbs are the most common on the market and can last between 460 and 1,000 hours, depending on usage.


Once you notice your bulb becoming dim, just replace it with a new one, and you’re good to go. However, if you linger, there’s no telling when it’ll finally give up and leave you stranded in the middle of the road.

How To Fix Dim Car Headlights and Bulbs?

To fix dim car headlights and bulbs, all you have to do in most cases is to replace them. In some cases, you can just clean the lights. However, if other sources are the cause, you’ll need to check to see if you can repair them.
Note that these solutions may apply even in a situation where low headlights are dim but brights work.

– Clean Cloudy Headlights With Toothpaste or Baking Soda

First, wipe all the dirt and debris on the headlights’ surfaces with a dry cloth, then spray some headlight cleanser over the surface. Allow the cleanser to soak all the gunk on the headlights’ surface before wiping them clean. Next, apply some toothpaste to the headlights and spread it across them in circular motions until you cover the entire surface. If you’re using baking soda, add a small amount of water to make it thick before applying it to the headlights.

Wait a few minutes to allow the toothpaste/baking soda to become semi-dry, then remove it with a toothbrush. Remember to remove it gently to avoid scratching the surface of the headlight and dot it in circular motions. By now, you should see the yellowish color of the headlights disappearing as you clean their surfaces. Finally, wipe the rest of the toothpaste/baking soda with a clean cloth.

– Replace Old and Damaged Car Bulbs

First, ensure your car’s engine is off and remove the key from the ignition. Next, open the hood and locate the headlight holder, which should be near the front of the vehicle. Once you locate the holders, disconnect the wires attached to the headlights. These wires supply the headlights when the electrical current to emit light.

Fix Dim Car Headlights and Bulbs

Now, take out the headlights and study how the bulbs are locked into them. If you’re unsure how to remove the bulbs, contact your car’s manual for assistance. Once the bulbs are out, you can replace them with new ones and re-attach the power lines. Note that this process may be slightly complicated in some vehicles due to the location of their headlights and wires.

– Changing a Damaged Alternator Belt

You’ll need to remove the old belt, and to do that, disconnect the battery’s negative terminal. This is to ensure the engine doesn’t start while you work on it and to keep you from injury. Now, carefully loosen the auto tensioner with a socket wrench by steadily moving it clockwise. This will relieve the pressure placed on the belt by the auto tensioner.

If your vehicle doesn’t have an auto tensioner, loosen the alternator bolts while tilting the alternator forward to slacken the belt. Ensure you take note of how the belt was wound around the alternator because that’s the same pattern you’ll have to follow. Now, you can slide the alternator belt off the highest pulley, then the lowest, and dispose of it.

Next, take the new belt and compare its length and width to the old one to ensure you have the correct belt size. Then guide the built through all the necessary pulleys, keeping tension on the belt to ensure it doesn’t fall off. If your vehicle has an auto tensioner, then lower its pulley with a wrench and put the belt around the pulley. Finally, put the belt around the alternator pulley and screw up the alternator bolts.

Frequently Asked Questions

– How Can You Increase the Light Intensity of Your Headlights?

The only way to increase the light intensity of your headlights is to replace them with LED bulbs or HID bulbs. Light Emitting Diode (LED) and High-Intensity Discharge bulbs are brighter than the popular halogen bulbs installed in most vehicles. They also last longer.

Dim Head Lights Solutions

Do Dim Headlights Occur as a Result of Using Different Bulb Types?

When comparing Nilight and Rovtop headlights, it is essential to understand if using different bulb types can lead to dim headlights. Factors like wattage, voltage, and beam pattern significantly affect the brightness of headlights. While both brands offer high-quality headlights, using mismatched bulbs may result in dim headlights due to variations in design and technology. Ensuring compatibility between the bulb type and headlight housing is crucial for optimal illumination on the road.


So far, we’ve discovered what causes dim headlights and how to increase headlight brightness in a car.

Here is a recap of the main points discussed in this article:

  • When both lights are very dim, maybe the lenses are discolored, the bulbs are dying, the ground wire is corroded or the alternator belt is worn-out.
  • A damaged alternator won’t provide enough electricity to power the headlights, leading to dull headlights; thus, implement methods on how to fix dim lights on a car.
  • One way to do that is to clean the headlights with a toothbrush or baking soda, but remember to turn the soda into a paste by mixing it with a small amount of water.
  • On how to fix dim LED headlights, clean them with a toothbrush or baking soda to remove any dirt on their surfaces.
  • A damaged alternator belt won’t produce enough power; thus, you need to replace it by following the process highlighted in the paragraphs above.

Replacing a damaged alternator is complicated and risky; therefore, we encourage you to seek the help of a professional if your alternator is broken. Also, if you try any of these solutions, including replacing the headlights, but it doesn’t work, contact an auto electrician for assistance.

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