Do Headlights Dim Over Time? (All You Need To Know)

Noticing that your headlights have lost some of their brightness since you first got them might raise some concerns over the seriousness of the problem.

So, if this is happening to your headlights, the information in this article will tell you everything you need to know about how it happens and when to expect it!

Do Headlights Dim Over Time?

Headlights do dim over time for a variety of reasons, such as the headlight lenses becoming fogged or yellowed. It might also happen due to the wiring becoming loose or corroded over time. Any problems with your alternator or its belt will also lead to dimmer headlights because of less reliable power supply.

Read on to learn everything you need to know about your headlights dimming over time, including a closer look into the causes, what to expect with LED, halogen, HID and xenon bulbs, and more!

Why Do Headlights Dim Over Time?

Your headlights might become dimmer over time for several different reasons, such as those listed below:

1. Fogged or Yellowed Lenses

Modern headlight lenses are made from polycarbonate acrylic that is more durable than glass, but it also reacts with ultraviolet light from the sun, becoming oxidized.

This is what causes them to become yellowed or cloudy and if it goes on long enough it’s going to significantly diminish the headlights’ brightness.

If the seal around the headlight lenses becomes worn and breaks, water droplets could make their way inside and condense, further limiting brightness.

2. Faulty Wiring

If the wiring in your lighting system has an issue, it’s likely going to affect how bright the bulbs can get.

In the case of your headlights, dimming from bad wiring is likely the result of the ground wire becoming corroded.

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Wires other than the ground wire can also cause this same problem if they get damaged or disconnected.

If you regularly drive off road, your car will experience a lot of vibrations that could dislodge wires that weren’t installed tightly. When you notice your headlights getting dimmer after you take your car off the pavement, this might be the issue.

3. Headlight Aging

3. Headlight Aging

If you’ve had your headlights for a while and you notice they’re getting dimmer, it’s probably because they’re nearing the end of their expected lifespan.

This is something that applies to HID and LED bulbs instead of halogens. Halogen bulbs don’t usually dim for this reason, they just stop working at once when they get old.

4. Alternator Problems

Your car’s alternator is responsible for providing power to most electrical components in your vehicle, including the headlights.

If it fails, your headlights will have to draw power from the battery, which is going to be in lower supply because it’s spread across more and heavier components.

Aside from the alternator itself, the alternator belt’s failure could also cause these problems. An alternator’s belt is what moves to generate the energy required to run the components and recharge the battery, so if it fails, power will be in limited supply.

Overall, both of these situations will result in dimmer headlights.

You can tell if this is the issue if your headlights dim when you perform certain power-intensive actions such as braking, using the sound system and more because the system is struggling to meet the increased demands.

5. Deposits on the Bulb Surface

This issue mostly applies to halogen bulbs. As you use them, the gas they contain burns and creates a substance that attaches to the bulb’s glass (think of it like smoke that gets on walls and darkens them).

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These bulbs use a filament that’s subjected to large amounts of heat and it might melt in certain parts, causing a similar effect.

Do HID Headlights Dim Over Time?

HID headlights will dim over time as they lose the chemicals inside the bulbs that are used to produce light.

Apart from this, the tube that is used to produce the electricity that charges the chemicals for light becomes stained and loses its effectiveness.

This process takes a very long time so it isn’t instantly noticeable until you drive in the dark and notice your headlights are significantly less bright than others on the road.

Do LED Headlights Dim Over Time?

Do LED Headlights Dim Over Time?

LED headlights will become dimmer over time, but this is a very slow process that is unlikely to affect most people. LED bulbs don’t produce heat and they have no moving parts, meaning they’re more durable than all other options used in headlights.

What might cause them to fade over time is vibrations from the vehicle that disconnect the threads inside its structure. As stated above, driving off road is likely to disrupt your car’s wiring. This is also a small but real danger to LED bulbs.

That said, LEDs last for tens of thousands of hours, so if you take care of your car as a whole, they’re probably not going to lose brightness.

Do Xenon Headlights Dim Over Time?

Xenon headlights are a subcategory of HID lights, so the same applies to them- they’re also going to dim over time.In this case, they use xenon gas and this is what gets depleted the more they’re used.

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Like other HID bulbs, it’s difficult to notice this as it happens, because it happens very gradually owing to their long lifespan.

Do Halogen Headlight Bulbs Dim Over Time?

Halogen bulbs will dim over time, but the effect is a result of deposits and other substances, creating an obscuring film on the bulbs or the headlight lenses. They don’t lose brightness due to age like other types of bulbs, however.

If everything else in the lighting system holds up, they can maintain the same level of brightness from the moment they’re installed until the end, whereupon they will just stop turning on at all.

Do Sealed Beam Headlights Dim Over Time?

Do Sealed Beam Headlights Dim Over Time?

Sealed headlights will dim over time as the lenses oxidize and become cloudy, fogged or yellow on exposure to the elements.

Moreover, depending on the type of technology used, they could lose brightness slowly over time as the bulb ages.

To know more about headlights, you can also check our posts about why do headlights flicker, when to use high beam headlights, and when to turn on headlights.


It’s not unusual for headlights to fade over time. It’s usually the result of faulty wiring, an issue with the alternator, impurities clogging up different surfaces and restricting the amount of light leaving the headlights or the bulb losing effectiveness with age.

LED, HID and xenon headlights are all susceptible to becoming dimmer over time due to the latter issue. Halogen bulbs also become dimmer because of how they produce light, which allows them to stay bright until the end when they stop working altogether.

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