The Audi A5 front turn signal requires a 12174NA, 12272NA, or H21W bulb size, while the rear turn signal uses a 921 bulb size. The replacement chart covers 2010 through 2014 production years with corresponding bulb size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The front turn signal on the Audi A5 uses one of three bulb types depending on the model year and headlamp configuration: 12174NA, 12272NA, or H21W.
The 12174NA and 12272NA are OEM part numbers with natural amber glass, both rated at 12V. Natural amber glass produces the required orange signal color without relying on a tinted lens or colored coating.
The H21W follows the ECE standard used in Europe and worldwide markets. It uses a BAY9s base, operates at 12V, and draws 21W. It is a single-filament bulb intended for signalling functions.
The BAY9s base on the H21W is an offset bayonet fitting, which physically prevents incorrect installation of a non-equivalent bulb type.
For the 2010-2012 Audi A5, the correct front turn signal bulb depends on which headlamp system is installed. Vehicles with halogen capsule headlamps use the 12272NA, while vehicles with HID headlamps use the H21W.
For the 2013-2014 Audi A5, the front turn signal uses the 12174NA regardless of headlamp type, representing a different fitment from the earlier model years.
The rear turn signal across the 2010-2014 Audi A5 uses the 921 bulb, an ANSI-standard wedge-type T15 bulb rated at 12V and 16W.
The 921 wedge bulb uses a plastic wedge base rather than a metal bayonet or screw fitting, making it a tool-free push-in replacement in compatible sockets.
For the 2013-2014 rear turn signal, the 921 is specified with a halogen capsule headlamp notation, indicating a headlamp-dependent fitment condition applies to those years.
The front and rear turn signals on the Audi A5 do not share a common bulb type across any model year, requiring separate part selections for each position.