Along with your brakes, the headlights in your vehicle are one of the most important safety features of your car and one of the most easily taken for granted. You probably rarely ever think about your headlights until such time as they're not working correctly. But without them, it's extremely unsafe for you to be driving in poor lighting conditions whether that means at night or in heavy rain and snow. And if you're suffering from dim headlights, that can be extremely frustrating and potentially dangerous as well.
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There are a number of reasons that your car may have dim headlights while you're driving. Let's take a look at some of the most common causes of dim headlights and what you can do to get it fixed if that's what you're experiencing.
Common Causes of Dim Headlights
If you're noticing that your headlights are dimmer than they used to be then there are a handful of common causes you might want to look into that could be the reason your lights aren’t shining as bright as they used to.
Bad Alternator: When your car is in motion every electronic system in the vehicle is powered by your alternator. Your alternator is powered by a drive belt connected to the engine. If there's a problem with your alternator, then all of your electrical systems are going to suffer as a result because your car simply can't produce the power needed to run everything. The first and most obvious victim of a bad alternator is often the headlights.
If you notice that your lights are bright when you first put the key in the ignition and then once you have the engine going they dim again, this is a very good sign that the alternator is the problem. When you first start your car the lights are going to be powered by your battery. Once the engine starts going the alternator takes over. So, when the lights go from bright to dim that’s the switch from battery to alternator. If your alternator isn't working properly then not only will your electrical systems fail, but you're also going to end up losing your battery as well because the alternator is what powers the battery while you're driving. Once that fails your car is not going to function any longer because you just won't have any electrical power whatsoever to keep it running.
If the alternator in your car has failed on you, the replacement cost can vary anywhere between $500 and $1,000 depending on the make, model, and year of your vehicle.
Loose Alternator Belt: Sometimes your alternator can still be perfectly functional but the belt itself is coming loose. The alternator belt attaches to a pulley which connects it to the engine so that it can maintain power. If the belt is coming loose then it won't have a firm grip on the pulley any longer which means that sometimes it will slip free and then grab hold again. When this happens, you'll notice your lights will brighten and then dim and then brighten and then dim. Fixing the belt will fix the problem and you don't have to worry about replacing the alternator.
If you need to replace the drive belt that connects your alternator to the engine it's probably going to cost you somewhere between $100 and $200 to get fixed.
Bad Battery: This can cause the dimming of your headlights not when you're driving so much as when you are first starting your vehicle or if you're sitting in the car without the engine running. If, when you first put your key in the ignition to get your car started, the headlights come on very dimly and then, as the engine takes over, they brighten up then that's a good sign that you have a problem with the charge in your battery.
Before your engine starts running the headlights are going to run off your battery power. Once your engine does get going, the alternator takes over. So if they are bright while you are driving and the engine is running, but they are dim when the engine is off then that is a clear sign you're running on poor battery power and your battery may be close to dying. If that's the case you either need to get your battery jump started, or you may need to buy a replacement battery. Replacement batteries can typically cost anywhere between $50 to over $200.
Corroded Ground Wire: The ground wire connects your bulb circuit to your car's chassis. The frame of your car is what serves as the ground itself. You have to connect jumper cables to part of the frame as well to ground it when you're getting your car boosted, for instance. When the ground wire that is connected to your lights ends up getting damaged because it's corroded or it's broken in some way then you won't have a consistent flow of power to your headlights and that can cause them to dim before they seem to burn out completely on you. Of course, the bulbs will not have actually burnt out, but there will be no power flowing to them, so they won't turn on.
Replacing a ground wire for your headlights is not going to cost a lot of money in terms of materials but you will have to pay for the labour if you're going to get a mechanic to do it for you. Since most mechanics charge by the hour, you're probably going to invest about one hour's worth of their time in the job so you could be looking at anywhere from $50 to $100 if you pay a mechanic to do it. If you're going to do it yourself, it's just the cost of a wire which is only a few dollars.
Old Bulbs: Most headlights are halogen bulbs. The manufacturer of nearly every vehicle uses halogen bulbs although you can buy aftermarket ones that are LED or something similar as replacements. However, if you still have your factory headlights then they are probably halogen. Halogen bulbs have gas inside of them which will discolor the actual inside of the glass over time. It takes quite a while, but it creates a hazy kind of smoky film on the inside of the class that will dim the light. When that happens the only thing you can do is replace the bulb with a new one to get it right again.
If you're just looking to replace the bulbs in your vehicle, you can probably get some new halogen bulbs for about $15 to $30 a piece. If you're looking for some brighter HID bulbs and you might end up paying in the neighbourhood of $100 or so for them. The entire headlight assembly however can cost anywhere from about $200 to $700 to get repaired.
How Can I Make My Headlights Brighter?
There are a few ways that you can brighten your headlights if the problem you're facing isn't related to the power supply in your vehicle.
Clean Your Headlights: This may sound kind of obvious, but a lot of people forget to clean their headlights when they're washing their car. And even then, the headlight covering may not be able to get as clean as it possibly can be with just a regular car wash. You can buy headlight cleaning kits that can really make the plastic covering your headlights clearer so that the light does seem brighter. It won't actually make the lights brighter than they're supposed to be, but it will return them to the brightness that they were when your car was a little bit newer and a little bit cleaner.
If you don't want to buy a kit, there are some simple DIY methods for brightening up your headlights by cleaning them as well. One of the simplest is just to use regular toothpaste and a toothbrush to clean the headlights off. This can scrub off any road grease and debris that has built up over time to create a film over your headlights.
Buy New Bulbs: This is another kind of obvious solution but if the problem you're having with your lights isn't related to the power supply, then you could just as easily buy some new light bulbs. There are many different kinds of lights available from premium halogen bulbs, to LED bulbs, to HID high intensity discharge bulbs. All of these can increase the intensity of your headlights, just make sure the kind you're buying are road legal and aren't going to be blinding other drivers on the road at night.
Do Headlights Dim with Age?
Believe it or not having dim headlights isn't always caused by a problem with your battery or your alternator. Halogen headlights do, in fact, dim over time. Any kind of light bulb will eventually grow dimmer on a long enough timeline. You can replace your standard headlights with some high-performance headlights that are going to provide a brighter more natural coloured light for a longer period of time if you want.
Be careful if you are replacing your factory headlights with new headlights as not every headlight is made equally. For instance, there are a number of LED headlights that you can buy which are incredibly bright but are not actually street legal. These lights are so bright that they can potentially blind other drivers and if you get caught using them you could face some serious fines. Always make sure that the headlights you're choosing are actually street legal and aren't going to potentially lead to accidents with other drivers. No doubt you've been on a road before and had another driver come up over a hill in front of you with light so bright for an instant you couldn't even see where you were going anymore. This is extremely dangerous and should be avoided at all costs.
How Long Do Different Kinds of Headlights Last?
If you're looking to get some new headlights, it's worth knowing how long you can expect the lights to last when you're in your vehicle. Let's take a look at some of the more common kinds and the lifespan that you can expect.
Tungsten or Halogen Bulbs: These are the typical kind of light bulbs that most headlights have installed in them and these are the cheapest ones that you can buy when you head to the store. You can expect about 1000 hours of life out of these kinds of light bulbs.
HID Bulbs: High intensity discharge bulbs are still halogen bulbs, but they are meant to last longer and be brighter. An HID light bulb should last 2000 hours in your vehicle.
Xenon Bulbs: Xenon is an alternative to halogen, and, like halogen, it is a gas. It has a much longer life span and should be able to last for about 10,000 hours before needing a replacement. Xenon bulbs can be as cheap as $50 a piece and can get well over $100 as well. Entire xenon headlights assembly may cost you between $700 and $1,000 but, as you can see, they last a very long time.
LED Bulbs: LED bulbs have the longest life span of any kind of headlight that you can buy. Some LED bulbs can last for as long as 30,000 hours. Again, just make sure the kind you're getting are street-legal and aren't going to potentially cause accidents with other drivers on the road.
The Bottom Line
There are a number of reasons your headlights can grow dim over time. Regardless of why your headlights might be going dim you need to make sure that you're keeping them as bright as you possibly can. It's a matter of safety not just for yourself but for other drivers on the road as well. Age, wear, and various mechanical problems can all lead to your headlights dimming on you eventually. If you let it go for too long, you could end up with the headlights burning out on you entirely leaving you in the dark at a critical moment. If you're noticing that your lights are dimmer than they used to be, get them cleaned up or fixed as soon as you can.