Why does my indicator flash faster after changing the bulb?

Fast flash usually means the new bulb has a different resistance to the original. For halogen replacements, ensure you have the exact same wattage. LED replacements require either a CANbus-compatible LED or an inline load resistor to mimic the resistance of the original bulb.

Is it an MOT failure to have a broken indicator bulb?

Yes. A non-functioning direction indicator is an MOT failure item. The test checks that all indicators flash at the correct rate and display amber light.

Can I fit an LED indicator bulb instead of halogen?

You can, but the LED must be road-legal (amber, E-marked) and must not cause fast-flash warnings. Canbus-compatible LED bulbs are the easiest solution for most modern cars.

How long do indicator bulbs last?

Standard halogen indicator bulbs typically last 2–4 years or 1,000–2,000 hours of use. Premium long-life variants from Osram and Philips can double that figure.

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Indicator Bulb buying guide — what to know before you buy

The direction indicator bulb — sometimes called a turn signal bulb — illuminates the amber indicator lens to signal a lane change or turn to other road users. UK law requires all direction indicators to flash at between 60 and 120 times per minute, and a failed bulb triggers the fast-flash 'bulb failure' warning on the dashboard. Modern vehicles use 12 V bayonet or wedge-base bulbs in W21W, PY21W, and WY21W base types, while many newer cars replace conventional bulbs with LED arrays. Osram and Philips supply high-quality OEM-specification direction indicator bulbs compatible with most European, Asian, and American vehicles. Replacing a failed indicator bulb takes under five minutes on most cars.

Identifying the correct indicator bulb

Indicator bulbs are amber or clear in colour — the lens colour determines which is needed. Using the wrong base type causes the bulb to sit at the wrong depth and flicker or fail prematurely. Always check the owner's handbook or use the vehicle registration lookup on CarParts247 to confirm the correct part.

PY21W (BAU15s offset pin): most common amber indicator bulb on European vehicles
WY21W (W3x16d): used on VAG group and some Ford models
W21W (W3x16d): clear bulb used where the lens provides the amber colour
T20 / 7440 (American base): found on some Mazda, Toyota, and Honda models
LED indicator replacements require a matched load resistor or CANbus-compatible bulb to prevent fast flash

Fitting a replacement indicator bulb

Most indicator bulbs are accessible from inside the boot or engine bay via a twist-and-pull bulb holder. Some vehicles require partial removal of the headlamp or tail lamp unit. Always switch the ignition off before changing a bulb, and avoid touching the glass of halogen bulbs with bare fingers — skin oils cause hot spots that shorten bulb life.