Audi S6 Turn Signal Bulb Size

Additional Notes

• The PY21W bulb follows the ECE standard used in Europe and worldwide markets. It is a single-filament amber bulb with a BAU15s bayonet base rated at 12V and 21W. On the Audi S6, it appears across both front and rear turn signal positions in multiple model years, making it one of the most frequently specified bulb types in these listings.
• The 3457NA and 3757NA are both ANSI-standard T25 wedge bulbs with natural amber glass, designed for the US and Canadian markets. The 3457NA is a dual-filament type rated at 12V with a 27W/7W output, while the 3757NA shares the same T25 form factor and 12V rating. Both are specified for the Audi S6 front turn signal positions in 2007-2011 model years, though each serves a distinct position and is not interchangeable with the other.
• The P21W and P21/5W are related ECE-standard bulbs that share a 12V, 21W rating but differ in base type and filament count. The P21W uses a BA15s bayonet base with a single filament, while the P21/5W uses a BAY15d bayonet base with dual filaments rated at 21W and 5W. These two bulbs are not interchangeable due to their different base configurations.
• The 12174NA and 12174SV share the same base part number but represent different variants. The 12174NA features natural amber glass, while the 12174SV is a Philips SilverVision halogen bulb with an enhanced coating. On the Audi S6, the 12174NA is specified for the 2023-2024 front turn signal, and the 12174SV is specified for the 2021 front turn signal. Despite their shared numeric origin, these variants are distinct products.
• The 12188 is a Philips halogen bulb designated for specialty applications, rated at 12V. It is specified for the Audi S6 front turn signal in 2013-2014, but only in vehicles equipped with HID headlamps. This conditional fitment indicates that headlamp technology on the vehicle directly affects the required turn signal bulb.
• The 12496 is a Philips/Osram halogen bulb for specialty applications, rated at 12V. It is specified for the Audi S6 front turn signal in 2010-2011 and for the rear turn signal in 2013, placing it across two different positions depending on the model year.
• The ECE-standard bulbs in these specifications, including the PY21W, P21W, and P21/5W, use bayonet-style bases with offset or indexed pin configurations. These configurations physically prevent incorrect installation of a bulb with the wrong base type, which is relevant given that the three ECE bulbs listed each use a different bayonet base.
• The front turn signal position on the Audi S6 shows variation across a wide span of model years, with bulb types ranging from the ECE-standard P21/5W in 1995 to OEM and Philips-numbered halogen types in later years. This variation reflects changes in lighting system design across different generations of the vehicle.