Instruction book Audi A3 Version Year 2013
Audi A3  Controls  Instruments and warning/indicator lamps   Warning and indicator lamps
If the indicator lamp or flashes, the turn signals are on. If both indicator lamps flash, the hazard warning lights are on.
If one of the indicator lamps flashes twice as fast as usual, a turn signal bulb has failed. Drive carefully to a qualified workshop without delay and have the fault rectified. While you are towing a trailer, the indicator lamp does not indicate turn signal bulb failures on the vehicle or on the trailer.
Note
For more information about the turn signals and hazard warning lights, refer to Link.

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