How A Car Bulb Works

There are a few different kinds of car bulb. The most common types these days are halogen bulbs and LED bulbs, and these work using rather different technologies. In general, though, car bulbs - whether warning lights, brake lights or headlights, are just like normal light bulbs in that they have a metal base which fits into the lamp itself. The contact between the base and the headlight unit allows electricity to flow in to the bulb and activate the filament.

The type of filament will vary depending on whether the light is a halogen light, or an LED (light emitting diode) bulb. But the general principle is the same in that it is the energy produced as the filament heats up which makes the bulb glow.

Types of Car Bulbs

The most popular kinds of car bulbs are halogen bulbs, high intensity discharge (HID) bulbs, and LEDs. HID lamps are made from metal halide, which is suspended in xenon gas, and this produces a very bright light. These bulbs tend to last a long time.

LED lamps are becoming increasingly popular as tail lights and accessory lights. They are quite a ‘cool’ light source, and they tend to last for a very long time. They are also very energy efficient. The main challenge with LED systems is that while the front of the lamps is very cool, the back end can become rather warm, which means that you cannot stack a lot of lamps together. The cumulative heat output can be a problem, and can shorten the life of the components significantly.

Halogen lights are a lot like the traditional incandescent lamps that were used in homes until relatively recently, when energy saving bulbs took over. Halogen lamps use a filament which is suspended in halogen gas. They produce very bright light, but they are relatively failure-prone.

How Long Does a Car Bulb Last?

HID lamps can last for as long as 2,000 hours of use, and LED lamps can last even longer. Halogen bulbs tend to last for just 450 to 1,000 hours, depending on the amount of heat they produce, and the level of usage that they are put under.

Why Do Car Bulbs Blow Or Burn Out?

Car bulbs will eventually fail. As halogen bulbs start to wear out the quality of the light that they emit degrades. The most common cause of bulb failures are the bulbs breaking (especially in a collision), or the bulb burning out because it is not sealed properly. Thermal failure is also an issue; the filament will slowly become more and more resistant to the flow of electricity, making the bulb get darker and darker, until eventually the electrical contact at the base of the bulb burns up.

Another common cause of failure is thermal shock. This happens when you turn on a bulb and the filament vibrates, then breaks. This is a part of the reason why bulbs tend to die just as you switch them on, but will last a very long time if they are left on all the time. Each time you turn a bulb on, it is stressed slightly. Bulbs in cars already face extreme variations in temperature, and stress from the weather, and tend to be turned off and on more often than bulbs in the home, so failures should be no surprise. In fact, it is impressive how long bulbs in cars do tend to last. In fact, one bulb failing can even cause the other to do the same!

There are a few different factors that will alter how long a bulb will last in a car. The thickness of the filament is something that will affect the failure rate, but there is not much that a designer can do here – the thicker the filament, the longer the bulb will last, but the less light the filament will produce. Thin filaments glow more brightly, but blow more quickly. The conditions that the car is exposed to matter too. Road vibration will shorten the life of your headlights, and electrical surges can be problematic as well. Filaments are very fragile, and will break easily. You can protect your bulbs by fitting them carefully – if you damage the glass while fitting the bulb, then it could blow far more quickly than it might have if you had handled the bulb with care.

At the end of the day you cannot stop a bulb from blowing if it is very old or badly made. You should get into the habit of checking your car on a regular basis to make sure that all the lights are working. If one does start to fade or give out completely, replace it immediately.

In many parts of Europe, it is a legal requirement to carry spare bulbs with you at all times. This is a good habit for motorists to get into, regardless of where they spend most of their time driving. If one of your bulbs does fail, we would recommend that you always consult your handbook for advice on fitting new bulbs.

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