The Audi A8 side marker utilizes a 12961 bulb size for illumination purposes within the exterior lighting assembly. Data for the specified component covers the range from 1997 through 1999.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Audi A8 front side marker position uses the 2357NA bulb across all model years from 1997-2003, making it the most consistently specified bulb in these listings.
The 2357NA is an ANSI-standardized bulb recognized in both the United States and Canada, carrying a BAY15d bayonet base and dual-filament construction rated at 12V with a 26.9W/8W output split between its two filaments.
The natural amber glass of the 2357NA produces its color through the glass itself rather than through a lens or coating, which is reflected in the "NA" suffix of its designation.
The BAY15d base of the 2357NA features two offset pins at different heights, a design that prevents incorrect single-filament bulbs from being inserted in its place.
The Audi A8 rear side marker for 1997-2002 takes the 12961, a Philips-designated miniature wedge bulb built on the T10 form factor with a W2.1x9.5d base, rated at 12V and 5W.
For the 2003 model year, the Audi A8 rear side marker specification changes to the 12821, also a Philips T10 wedge bulb sharing the same W2.1x9.5d base and 12V, 5W rating as the 12961.
Because the 12821 and 12961 share the same base type, voltage, and wattage, the physical and electrical characteristics of the two bulbs are identical according to the provided specifications, though they carry distinct Philips part numbers.
The W2.1x9.5d wedge base used by both rear side marker bulbs is a press-fit connection with no locking pins, relying on the tension of the socket to hold the bulb in place.
The front and rear side marker positions on the Audi A8 are not interchangeable, as the front uses a dual-filament BAY15d bayonet bulb while the rear uses a single-filament wedge-base bulb, representing fundamentally different base types and wattage ratings.
The 2357NA specified for the front side marker carries a significantly higher wattage on its primary filament at 26.9W compared to the 5W rear side marker bulbs, reflecting a difference in the light output demands of the two positions.