Why is my turn signal blinking fast?
The short answer
When one side blinks fast and the other blinks normally, the car is telling you a bulb on the fast side has stopped working: front, rear, or the small repeater on the side mirror or fender. Cars do this on purpose (it’s called hyperflash) so you notice. Replacing the dead bulb, or the LED unit, usually fixes it.
Is it safe to drive? Safe to drive
The car is safe to drive, but other drivers may not see you signalling on that side, and a working signal is a legal requirement. Use hand signals if you need to, and fix it within a few days.
Why a dead bulb makes it blink faster
The flasher circuit measures how much current the bulbs on that side draw. When one bulb burns out, the current drops, and the car flashes the remaining ones at double speed as a warning. Only that side is affected, which is why the other side blinks normally.
Finding the bulb that’s out
- Switch on the hazard lights (both sides flash) and walk around the car. Check the front corner, the rear light, and the side repeater on the mirror or front fender.
- Check both front and rear: many cars have a separate signal bulb in each.
- Look at the dash arrow too. If both arrows blink fast with the hazards on, it may be the trailer light circuit or the flasher itself.
If every bulb works
- Wrong bulb type: a replacement bulb with a different power rating, or an LED bulb fitted where the car expects a normal bulb, draws less current and triggers hyperflash. LED upgrades usually need a resistor or an LED-compatible flasher.
- Corrosion in the bulb socket: a green or white crust stops the bulb from making good contact. Common in tail lights where water gets in. Cleaning the contacts often fixes it.
- A loose or damaged connector after bodywork, a new bumper or a tail light replacement.
- A trailer plugged in, or a trailer wiring module fault.
- On newer cars with LED signals, the LED module itself fails and is replaced as a unit, sometimes the whole headlight or mirror cap.
What the repair usually involves
A conventional bulb is usually a few minutes’ work and a few dollars: the owner’s manual shows how to reach it, often from inside the trunk or behind the headlight. Buy the exact bulb number from the manual or the old bulb.
If the signal is part of an LED headlight, tail light or mirror, the part costs more and must match the car’s exact trim and options. That’s where a VIN check avoids ordering the wrong unit.
What to tell your mechanic
- Which side blinks fast, and whether the dash arrow does it too.
- Which light you found out (front, rear or side repeater).
- Any recent bulb changes, LED upgrades, bodywork or trailer use.
General guidance for common cases, not a diagnosis of your car. If a problem affects brakes, steering, tires or anything else that keeps you safe, have the car inspected by a qualified mechanic.