Turn Signal Lights

Turn signal lights (also called indicators, blinkers, or direction indicators) are amber-coloured flashing lights positioned at the front, rear, and sides of a vehicle that signal the driver's intention to change direction or lane. Modern vehicles use amber indicators at all four corners plus repeater indicators on the front wings or integrated into the door mirror housings. In some markets, both side repeater positions are mandatory; in others, one or the other is acceptable. The turn signal circuit uses a flasher unit (or in modern vehicles, a function integrated into the Body Control Module) to interrupt the circuit at a regulated rate of 60–90 flashes per minute, producing the characteristic rhythmic flashing. The rate of flashing is carefully regulated — flashing too quickly (a hyperflash condition) or too slowly both indicate a circuit fault. Hazard lights use the same lamp assemblies, activating all four corners simultaneously to warn other road users of a stationary vehicle or emergency. LED indicators have become standard on modern vehicles, providing consistent light output throughout their service life and avoiding the gradual dimming of aging halogen bulbs.

Turn signals communicate directional intent to other road users in a universally understood visual language — a flashing amber light at any corner of the vehicle signals a pending directional change. The flashing pattern is deliberately intermittent rather than steady — the intermittent flash has higher attention-attracting properties than a steady light, particularly in peripheral vision, where sustained steady signals are easy to overlook. The prescribed flash rate of 60–90 per minute is standardised internationally to ensure other road users can anticipate the vehicle's intention with a predictable timing pattern. The side repeater indicators serve to alert pedestrians and cyclists approaching from the side, and other drivers during overtaking manoeuvres, providing directional information that the front and rear indicators may not be visible for from certain angles. Hazard lights are used to indicate that the vehicle is a stationary hazard (breakdown, accident, obstruction) — using hazard lights while driving is sometimes permitted in some markets to warn of sudden heavy braking ahead, though practices vary by jurisdiction.

Hyperflash (rapid flashing): The most common indicator fault. When one turn signal bulb on the circuit fails (a front or rear indicator lamp), the reduced circuit resistance causes the remaining indicator on that circuit to flash at double speed. This is not simply an aesthetic issue — rapid flashing is the designed warning signal for a bulb failure in the circuit. It makes the remaining indicator less effective at communicating to other drivers and is a legal fault. Replace the failed bulb immediately.

Indicator not flashing on one side: A failed flasher relay or BCM output fault causes the entire side to not flash. Test by noting whether the dashboard indicator symbol illuminates at normal or rapid rate — if neither front nor rear indicators flash on one side, the issue is the flasher unit or circuit feed, not an individual bulb.

Wing mirror indicator failure: Mirror-mounted LED indicators are complex assemblies that can fail with condensation, impact damage, or connector corrosion. Replacement usually requires the complete mirror cover assembly.

Level 1 — Regular Function Check: Test all four turn signal positions monthly — walk around the vehicle while activating left and right indicators to confirm all four corners are flashing. Check that the dashboard indicator light flashes at the correct rate (60–90 flashes per minute) — rapid flashing signals a failed lamp. Also check hazard lights operate on all four corners. Repair any failed indicator before the next drive.

Level 2 — Bulb Replacement: Accessing turn signal bulbs varies significantly between vehicles. Front indicators are typically accessed through the headlight assembly or through a panel behind the wheel arch liner. Rear indicators are accessed through the boot or through a panel inside the boot. Consult the owner's manual for the correct access procedure. Replace with the correct bulb type (and wattage) — using a higher-wattage bulb than specified increases circuit resistance faster and can cause rapid flashing even with a working bulb.

Level 3 — Fault Diagnosis for LED Circuits: Hyperflash in LED turn signal systems is typically caused by a resistor that is no longer present in the circuit — aftermarket LED replacement bulbs may require load resistors to replicate the current draw of the original halogen bulbs. Without the correct load, the BCM detects an open circuit and flashes rapidly. Professional diagnosis is needed to correctly integrate LED bulbs into turn signal circuits with BCM-controlled flash rates.