Car Headlight Bulb Sizes

Car Headlight Bulb Sizes

Buying the correct light bulb to fit your vehicle can be very confusing. Firstly, there are different functions of bulb – headlights, tail light, indicator lights to name a few. In this article, only headlight bulbs are going to be discussed.

It is essential that one gets the correct size to fit your particular vehicle, for a number of reasons.

What do the numbers mean?

There are numerous configurations of letters and numbers that are used to depict what the size of each particular bulb is. For example you will get an H4 bulb, or a 9005 size bulb. What these numbers and letters actually mean is not important when finding the correct replacement headlight bulb for your car, but it is important that the correct one is purchased.

There are a couple of reasons for this. Firstly, the fittings on the bulb will match the socket where it is to be fitted on your vehicle. If you have the incorrect bulb, you may very well end up being very frustrated that the bulb will not fit. Even if it looks the correct size, make sure you have the correct number to ensure it is exactly the right one.

Secondly, the bulbs are made differently. What is meant by this is that some are single filament bulbs and some are double.

The double ones will have one filament for the high beam and one for the low. In other cases, there are actually two bulbs for each of these functions. So if you get a bulb with a single filament that happens to fit the socket of where your double filament bulb is meant to go, you may very well not be able to have high beams, or low beams, or both!

Thirdly, the bulbs are different dimensions, meaning that they will fit properly into the space provided by the design of the headlight. If they are the wrong size you may not have enough space to fit them

Retro fits

These days one has the option of more than just the standard fitting bulb. If your car comes standard with a halogen type bulb, you have the option of Xenon or LED bulbs. The sizes apply to these retro fitted bulbs too.

It must be noted, however, that most of the Xenon and LED bulbs have extra pieces added into the design.

Items such as power packs and cooling fans have had to be included because of the specific functioning of these bulbs. This makes for larger overall units, which sometimes makes it difficult to fit directly into the space provided for a bulb. With this in mind, even if the correct size if bought, some adaptations may be necessary in order to fit the bulb into the car.

Furthermore, some of these upgrade kits may not work when first fitted. This may not necessarily have to do with the bulb being the incorrect size, but may have to do with the polarity of the bulb or incompatibility of the bulb to the vehicles electronics.

To fix the polarity issue simply flip the bulb in the socket in order to get it to work. Incompatibility is a bigger issue and contacting the supplier is recommended to find a solution for this problem.

How to find the correct size

So how do you go about ensuring you have the correct size bulb?

The obvious first place to check is on the bulb you need to replace. The size will be on the underside of the casing. Look for a number or a number combined with a letter.

The next choice is to go to your nearest agent or motor parts dealer. The information you need to take with you is the vehicle make, model and year of production. They will be able to tell you the correct size bulb you require.

Alternatively, you can go to any “online bulb finder” where you can enter your vehicle details and find out the size of the bulb required. Often these sites will allow you to go purchase online.

If you are wanting to upgrade, then purchasing an upgraded retro bulb kit online via sites such as Amazon is possible. Your agent or parts dealer may also have retro kits. In these situations it is essential that you have the correct size.

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