Audi S5 front turn signal bulbs use 12174NA, 12174SV, or H21W sizes, while rear turn signal bulbs use 921 size. The replacement bulb chart covers 2008 to 2024 production years.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The 12174NA is the most frequently specified front turn signal bulb across the Audi S5, covering model years 2013-2019 and 2022-2024. It is an OEM-designated part with natural amber glass and operates at 12 volts.
The H21W bulb follows the ECE standard, which governs lighting equipment across Europe and many international markets. It uses a BAY9s base, operates at 12 volts, and draws 21 watts. On the Audi S5, it was the specified front turn signal bulb for 2008-2012.
The 921 is an ANSI-standard wedge bulb of the T15 type, rated at 12 volts and 16 watts. It served as the rear turn signal bulb for the S5 across 2008-2016.
The 2021 Audi S5 front turn signal specification calls for the 12174SV rather than the 12174NA used in surrounding years. The 12174SV is a Philips SilverVision part featuring an enhanced coating and operates at 12 volts.
The 12174NA and 12174SV share the same 12-volt operating requirement but differ in construction and origin. Substituting one for the other may affect light output characteristics, as the SilverVision variant carries a specialized coating not present on the natural amber OEM version.
The 2019 Audi S5 front turn signal specification for the 12174NA is conditioned on the presence of HID headlamps, indicating that headlamp type is a relevant fitment variable for that model year.
The H21W and 921 bulbs are not interchangeable. The H21W uses a BAY9s bayonet base and draws 21 watts, while the 921 is a wedge-type bulb rated at 16 watts, making them physically and electrically incompatible despite both being single-filament signalling bulbs.
The front turn signal specification shifted from H21W to 12174NA between the 2012 and 2013 model years, reflecting a change in the bulb standard from ECE-based to an OEM-designated part number.