Audi S5 Turn Signal Bulb Size

Additional Notes

• 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.