Indicator Light Bulb change & replacement made easy

How does an indicator light bulb work?

Indicator light bulbs, also known as turn signals, are mounted on each corner of your car, along the side wings, and often in the door mirrors. Their job is simple but essential: they signal to other road users when you intend to turn, change lanes, or pull over.

Behind each amber or clear lens sits a single bulb: clear lenses use amber bulbs, while amber lenses work with clear bulbs.
When you flick the indicator stalk, an electrical circuit closes and sends power to that side’s indicator bulbs. The current passes through a flasher relay or the body control unit, which rapidly opens and closes the circuit to create the familiar on-off “winking” effect. For your hazard warning lights, the same principle applies, but both left and right circuits are powered together, so all four indicators flash in unison.

A working indicator bulb is crucial for safe and legal driving. If a bulb burns out, the system can’t flash correctly, and your car may either flash rapidly or not at all, a common warning sign of a failed indicator bulb.

What does an indicator light bulb change job involve?

Here’s an overview of what a mechanic will generally follow when changing a faulty indicator bulb:

• The mechanic confirms which indicator isn’t working and checks whether the issue is caused by the bulb itself, a wiring fault, the holder, or the flasher relay/body control module.
• Depending on the location - front, rear, side repeater, or mirror - access may involve removing part of the headlamp or tail light cluster, unclipping the side repeater, or detaching the mirror casing. Some cars offer simple twist-out holders, while others require more involved access.
• The faulty bulb is carefully twisted or unclipped from its socket. The mechanic checks the holder for corrosion or heat damage, which can also cause intermittent or fast-flashing indicators.
• A manufacturer-approved amber or clear bulb (depending on your lens type) is fitted securely in the holder. For LED indicator units, the entire light module may need replacing. The mechanic ensures a clean connection for proper flashing.
• The mechanic switches on the indicators and hazard lights to confirm the new bulb flashes at the correct speed and brightness. They also check the opposite side to ensure even performance.

How do I know when I need an indicator light bulb change?

Spotting a faulty indicator bulb early helps keep you safe and avoids fines or an MOT failure. Here are the most common warning signs:

• Faster “Hyperflash” – If one bulb fails, many cars will flash the remaining lamps much more quickly than normal.
• Dashboard Warning – Some vehicles display a “bulb out” icon or message when an indicator isn’t working.
• Service Reminder – Your mechanic may flag a dim or non-functioning indicator bulb during routine maintenance.
• MOT Failure – A blown indicator will cause your car to fail its safety inspection.

Indicator bulbs can simply blow after thousands of flashing cycles, but sometimes the real culprit is a blown fuse, corroded socket, or damaged wiring that needs fixing. Since driving without fully functioning turn signals is both dangerous and illegal, have any suspect indicator lamps checked and replaced as soon as possible.

Can I change the indicator light bulb myself?

Replacing a blown indicator bulb can be a straightforward task if you’re equipped with the right tools and some technical skills. You’ll need the correct bulb (check your owner’s manual or existing bulb type) and a tool like a screwdriver, you can usually access the bulb holder, twist or pull it out, and fit the new bulb. Wearing gloves is a good idea, as touching the glass on halogen bulbs can shorten their lifespan.

Once the bulb is fitted, switch on your indicators and hazard lights to make sure it flashes at the correct speed and matches the brightness of the opposite side.

However, not all cars make this process easy. On some models, the indicator bulbs are tucked behind wheel-arch liners, inside complex headlamp units, or integrated into door mirrors. If access is tight, if the housing is cracked, or if the wiring or socket looks damaged or corroded, it’s best to book a mobile mechanic. They can check the full indicator circuit, fit the correct replacement, and ensure everything works safely.

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

Yes, driving with a faulty indicator light is illegal in the UK. Under the Road Vehicles Lighting Regulations 1989, all of your vehicle’s indicators must work correctly at all times. A defective turn signal is considered a safety-critical fault, because it prevents you from clearly communicating your intentions to other road users.

If the police stop you for a non-working indicator, you may be issued a Vehicle Defect Rectification Notice, giving you 14 days to repair the fault and provide proof. Ignoring the notice can lead to fines, and in some cases, penalty points on your licence or further action if the issue contributes to unsafe driving.

A faulty indicator will also cause your car to fail its MOT, as functioning indicators are a basic roadworthiness requirement.
Beyond the legal implications, a broken indicator greatly increases the risk of collisions, especially when turning, changing lanes, or pulling out of junctions. If you notice rapid flashing, no illumination, or intermittent operation, have the indicator checked and replaced by a qualified mechanic as soon as possible to stay safe and fully road-legal.

How much does an indicator light bulb change cost?

The cost of replacing an indicator light bulb can vary depending on the type of bulb your car uses and how accessible the unit is. For many vehicles, it’s a quick and inexpensive job, especially when standard bulbs are used.

The part itself is inexpensive, the cost of an indicator bulb replacement is around £10–£20 for a standard front or rear side indicator on many common cars. However, if your car is fitted with LED indicator units or the bulb is built into a more complex light assembly, the price can be higher due to the parts and time involved. Ultimately, the cost will depend on your specific car and the parts your manufacturer recommends. To see how much you could save by booking with ClickMechanic, try our free price estimator tool!

What does a ClickMechanic indicator light bulb change quote cover?

Unless otherwise stated, the quote will cover:

• The cost of the indicator light bulb(s)
• 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 indicator light bulb?

Yes, a mobile mechanic can usually replace an indicator light bulb without any trouble. Since most indicator bulbs are relatively easy to access, this type of job is well-suited to be done outside of a traditional garage, right on your driveway or at your workplace. The mechanic will bring the right tools and replacement parts, inspect the system to make sure it’s just the bulb that needs replacing, and then fit a new one. They’ll also check that everything works properly before they leave, so you can get back on the road safely and legally.