Fact: your car's dipped headlights and main beam headlight bulbs won't last forever. Eventually, they'll blow and you'll need to replace them.
Most cars' headlights house three types of bulb; the dipped/main beam bulb (which many people refer to as the headlight bulb), the sidelight and, in some newer cars, the indicator bulb. For more information on the rest of your headlight bulbs head here.
How do you change a headlight bulb? The vast majority of cars allow you to access the bulbs from the rear of the headlight unit, where the cover can be unclipped and the bulbs accessed. Sometimes it's not so simple, because the car's battery, air intake or other component obstructs access to the rear of the headlight. Your Haynes manual will show you if anything needs to be moved, and how to do it, to access the headlight bulbs. More on this below.
In the worst case scenario, you'll need to remove the bumper, but this is rare.
Different dipped headlight bulbs
Filament/Halogen bulbs
These dipped headlights and main beam bulbs are generally fitted to all cars prior to the advent of HIDs, and many cars still use them. They operate on the same principle as a household lightbulb, with a very thin metal filament heated by an electric current.
Most car filament headlight bulbs are filled with one of the halogen gases. These types of bulbs are cheap and long-lasting. You can get so called 'high power' bulbs, which are direct replacements for the originals. While these may offer an improvement over the standard light, don't expect them to be a lot brighter.
You may also have seen 'xenon-style' bulbs, which will emit a whiter, less yellow light. Don't confuse these with xenon HID lights, because they aren't the same thing.
Xenon HID bulbs
High-Intensity Discharge (HID) bulbs are the ones most often found on newer cars that give off the whiter, brighter light.
HID bulbs don't have a filament, but instead use a pair of electrodes in a glass tube. The tube is filled with xenon gas and they work on a 'gas discharge' principle. They need what's known as a 'ballast' to operate this is a small electrical box which starts the lights and controls their operation.
Want to upgrade your halogen headlights to HIDs? You can get aftermarket-HID kits but you can't fit them to every car, so it's probably best to stick with like-for-like, unless you've done your homework.
When xenons near the end of their life they flicker, and the colour of the light output may also change slightly. When they do fail you'll find they cost substantially more to replace than halogen bulbs.
LED bulbs
Only on the very newest cars will you find LEDs used for the dipped headlights and main beam, and a growing number of models have 'adaptive' LEDs, which activate and deactivate depending on the location of other road users, to avoid dazzling them.
You can exchange some filament bulbs, such as sidelights and indicator bulbs for LEDs with the same fittings, but these can cause issues with some cars because their power consumption is so low that the car thinks the bulb isn't functioning and flags up a dashboard warning.
If you do intend to fit LEDs look for CANbus LEDS' as these incorporate a resistor, which mimics the effect of a regular bulb. However it's not advisable to fit CAN bus LEDs on a non-CANbus car, so you must check before fitting.
You can't swap halogen or xenon dipped and main beam headlight bulbs for LEDs, though, because this will cause the car to fail the MoT test.
What does H1, H4 and H7 mean on headlight bulbs?
Bulb types are commonly referred to using codes such as 501, H1, H4,or H7. These should be replaced like-for-like and your handbook should tell you what bulbs you need.
Alternatively, you can remove yours and check before buying.
How to change your dipped headlights and main beam headlights bulbs
- To locate the bulb that's failed turn the lights on and see which bulb has blown. Note its location to make sure you replace the correct one.
- Most cars have a cover on the back of the headlight that can be unclipped and the rear of the bulbs accessed. You may need to remove components to gain access (commonly the battery) but you may be lucky and have one that can be swapped with everything in-situ.
- One you've got access by removing the headlight cover (or in some cases the whole headlight) remove the connector on the back of the bulb you wish to replace.
- There's likely to be a metal spring clip holding the bulb in the light so unclip this and the bulb will drop out. Some smaller lights require you to turn the fitting anti-clockwise.
- When you replace any bulbs, but particularly the headlight bulbs try not to touch the glass part of the bulb. Oil from your skin can cause hotspots on the glass, which may lead to premature bulb failure.
- Be warned that there are some cars where access is more difficult, requiring wheels, or even the bumper to be removed. So make sure you know how yours fit before embarking on the job.
Arm yourself with the required knowledge before tackling the task – and always test that the bulb works before installing any covers (and replacing any components that had to be removed to access the bulbs).