Headlamp Bulb replacement & repair made easy

How does a headlamp bulb work?

Headlamp bulbs are your car’s main source of forward illumination, lighting the road ahead so you can see and react to obstacles, road signs, and other vehicles, especially at night or in poor weather. Most cars come equipped with two or four headlamp units at the front. Some use a single dual-filament bulb that switches between dipped (low) and main (high) beam, while others have separate bulbs dedicated to each beam setting.

Inside the headlamp housing, the bulb generates a strong, focused beam of light. This light is directed by a precision-shaped reflector and projected through a clear lens to create a wide, even beam pattern on the road. This ensures good visibility without dazzling oncoming traffic.
If a headlamp bulb becomes dim, damaged, or fails completely, your visibility drops significantly. This can leave dark areas on the road, reduce your reaction time, and increase the risk of accidents, and driving with a faulty headlamp is also a legal offence under UK road lighting regulations.

What does a headlamp bulb replacement job involve?

Keeping your headlamps fully functional is essential for safe night-time and poor-weather driving. Here’s how a mechanics generally handles a headlamp bulb change:

• The mechanic checks which headlamp bulb has failed and confirms whether the issue is with the bulb, wiring, fuse, or headlamp unit itself.
• Depending on the vehicle, the mechanic may access the bulb from behind the headlamp, through the wheel arch, or from underneath the bumper. Some modern cars require removal of trim panels or even loosening the headlamp unit.
• The faulty bulb is disconnected from its wiring connector and carefully unclipped or twisted out of the housing. Care is taken not to damage the reflector, housing, or seals.
• A manufacturer-approved bulb of the correct type and wattage is fitted. The mechanic avoids touching the glass (especially on halogen bulbs), as fingerprints can shorten bulb life.
• After fitting, the headlamp beam pattern is checked to ensure it’s correctly aligned and not angled too high or too low. This helps ensure safe visibility without dazzling other drivers.

Both dipped and main beams are tested to confirm full functionality, and the mechanic may check the remaining exterior lights for safety.

How do I know when I need a headlamp bulb replacement?

If a bulb is on its way out, you may spot one or more of these warning signs:

• Poor night-time visibility: You struggle to see the road ahead as clearly as you used to, even on a full beam.
• Only one headlight is shining: You notice the reflection of just one beam when you should see two.
• Service centre advice: Your mechanic points out a dim or non-functioning bulb at your last service.
• MOT failure: Your vehicle fails its MOT due to a faulty or missing headlamp bulb.

If you notice any of these signs, it’s time to replace your headlamp bulbs.

What is the difference between an H4 and H7 bulb?

Choosing between H4 and H7 bulbs depends on how your car’s headlight system is designed:

• H4 bulbs (dual-filament):

An H4 bulb contains two filaments in one unit, meaning a single bulb provides both low beam (dipped) and high beam (main). Cars that use a single headlamp housing for both beam settings typically take H4 bulbs.

• H7 bulbs (single-filament):

An H7 bulb has one filament, so it’s dedicated to either low beam or high beam. Vehicles with separate low-beam and high-beam reflectors or projectors use two bulbs per headlamp (one H7 for each function).

Light output and performance

H4 and H7 bulbs also differ in their brightness and beam characteristics:

• H4: Around 1,000 lumens on low beam and 1,650 lumens on high beam.
• H7: About 1,500 lumens in its single, focused beam.

Because an H7 is designed to fire one stronger beam, it often gives a crisper and more focused light pattern, which can improve night-time visibility.

Is it illegal to drive with a faulty headlamp in the UK?

Yes, driving with a non-functioning headlamp is illegal under UK law, which requires both your dipped and full-beam lights to work correctly at all times. If your headlamp is dim, flickering, or out completely, you could be stopped by the police and issued a Vehicle Defect Rectification Notice requiring repair within 14 days, face a £50 fixed penalty (or even penalty points in more serious cases), and fail your MOT until the issue is resolved.

To stay safe, avoid fines, and keep your car legal, it’s best to arrange a prompt repair to restore full headlamp functionality.

How much does a headlamp bulb replacement cost?

The cost of a headlamp bulb replacement typically ranges from £60 to £130, depending on your vehicle and the type of bulb it requires. Some cars use standard halogen bulbs, while others may use more expensive Xenon or HID bulbs, which can increase the cost. Labour charges can also vary depending on how easy or difficult it is to access the bulb in your particular car model.
Ultimately, the total cost will depend on what your manufacturer recommends for your vehicle. Use our free price estimator tool to find out what you could save by having your headlamp bulb replaced by ClickMechanic!

What does a ClickMechanic headlamp bulb replacement quote cover?

Unless otherwise stated, the quote will cover:

• The cost of the headlamp bulb
• Coming to you
• Fitting of the parts
• Disposal of the old parts (unless you request to keep them)
• VAT (if applicable)
• 12-month parts and labour warranty

Can a mobile mechanic replace the headlamp bulb?

Yes, replacing a headlamp bulb is one of the simplest jobs a mobile mechanic can perform at your home or workplace. Since headlamp access usually only requires opening the bonnet and reaching into the light housing, no special workshop equipment or ramps are needed. A qualified technician will arrive with the correct bulb for your make and model, remove the old lamp, fit the new one, and test your lights to ensure they’re aligned and working properly.