Choosing and fitting replacement car bulbs

  • 3,538

There are many different types of car bulbs available, and it's a bit of a minefield, but what's the difference between them, and how do you change them?

If there’s a time of year when your headlights are important, it’s the winter! It’s not uncommon to have to drive to and from work in the dark, so always make sure your lights are working as they should. If you do have one of your lights fail, you need to know what to do, especially as not all cars have the same bulbs and there are many different sizes and types. We'll go through the main ones you're likely to come across to help you find the right one for your car.

In your headlights you're likely to find three different bulbs – The main/dipped beam, the sidelight and, in newer cars, the indicator (some older cars have the indicator as a separate unit). You may also find 'DRL' driving lights (which come on whenever the car is on), and occasionally cornering lights that swivel in the same direction as the front wheels.

The rear light clusters generally have taillights which may also incorporate the brake light (known as stop and tail lights), indicators, reversing lights (or light), fog light (or lights) and there will be a high-level brake light in the middle.

Handy parts and tools

Types of bulbs

Halogen/filament

These are the ones conventionally fitted to all cars prior to the advent of HIDs. They work like a household bulb whereby an electrical current heats up a thin metal filament housed in a glass bulb (filled with halogen gas if they're the headlights). They're cheap, last a decent amount of time and are easily swapped. There are plenty of 'high power' performance bulbs on the market, that promise to give a lot more light. While they are an improvement over standard they won't be massively brighter, so don't expect miracles, or pay over the odds. There are also bulbs that give off a whiter 'xenon-style' light, and claim the halogen gas has been replaced with xenon, but don't confuse xenon-filled bulbs with genuine xenon HIDs. They aren't the same thing. Bulbs fitted to the rear of the car are also commonly filament style, but without the halogen filling.

Handy parts and tools

Xenon HID

HID stands for 'High Intesity Discharge' and these are the ones on newer cars that give off a much brighter, whiter light. They work in a different way to regular filament bulbs in that an ark of light is created by a pair of electrodes in a glass tube containing xenon gas. As mentioned these aren't the same as xenon-filled filament bulbs. They work on a 'gas discharge' principle and cost a lot more than regular bulbs. They need a 'ballast' which is a small box of electrics which start and control the light output, so you can't simply swap halogens for HIDs. Aftermarket HID conversions are available, but fitting them is a minefield requiring an article in itself – so our advice is to stick with like-for-like unless you've conducted plenty of research.

Expert tip

When HIDs near the end of their life they can flicker on and off, unlike halogen bulbs which simply stop working. Don't confuse the flickering with a faulty connection. The light emitted may change colour during this time too, so you know it's time to change them.

Handy parts and tools

LED Bulbs

On all but the very newest of cars, LEDs aren't used for the main/dipped headlight – but as the light output doesn't need to be as bright they can be used as sidelights. If you want to swap your filament sidelights for LEDs be aware that on many cars it can cause issues with flickering, and also trigger 'bulb failure' dash warning lights due to the much lower current required to power them. You need to look for 'CAN bus LEDs' which are fitted with a resistor to simulate the effects of a regular bulb, and so don't trip the warning lights. It's not advisable to fit CAN bus LEDs on a non-CAN bus car, so check before fitting.

Handy parts and tools

What bulbs do I need?

You may see reference to codes such as H1, H4, H7, or 501. These refer to the style of bulb and should always be replaced like-for-like. Your car's handbook should tell you what various bulbs you need, and also details of the fitting procedure. If you don't have access to your handbook then a Google is in order to find the answer!

Handy parts and tools

Replacing your bulbs

First ascertain the location of the bulb that you wish to replace. Simply turn the lights on and identify where it is within the light housing. If you're lucky you'll have a vehicle where the bulbs can be replaced in-situ – there will be a cover on the back of the light unit which is held on by plastic or metal clips – with this removed the connector can be removed from the back of the bulb, and the bulb removed usually via a metal spring clip. Remove the connector BEFORE removing the bulb, as it can be tricky to do otherwise. Some bulbs are a twist fit, and turning them anticlockwise will free them from the housing.

Some cars require the headlight to be removed to give access to the bulbs – which can be as simple as a couple of bolts, or an involved full-on bumper-off job! So make sure you know before you start.

Rear light bulbs are commonly accessed either via a hatch/flap inside the car or by removing the light clusters. Once again consult the handbook for details on how to access or remove yours. Most rear lights are a 'twist fit' – and again, carefully remove the connector (which may be very stiff) before freeing the bulbs.

Expert tip

Whenever you replace bulbs, especially headlights – take care not to touch the glass. Oil from your fingers can cause hotspots which can lead to early bulb failure.

Expert tip

If you find your headlight filling with condensation after changing bulbs check you've replaced the rear cover properly. Once you've fitted the cover correctly you can dry the condensation with a hairdryer!

Get Winter Ready

All the car parts and expert advice you need to keep safely on the road. Expert Tips and Advice for Winter