Audi S4 Back Up Light Bulb Size

The Audi S4 back up light bulb uses 2 distinct sizes: 921 and 7506, with each bulb size corresponding to specific vehicle production years. The replacement chart covers the 1992 to 2024 model year range for this component.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Bulb Size by Year Range

Years	Bulb Size
2023-2024	921
2020-2021	921
2009-2016	921
2007-2008	7506
2000	7506
1992-1994	7506

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Wedge bulb (T15). 12V, 16W.	921

Other Locations

Additional Notes

The Audi S4 backup light bulb specification uses two distinct bulb types across its model years: the 921 and the 7506.
The 921 is an ANSI-standard bulb recognized in the United States and Canada, built on a T15 wedge base, and rated at 12 volts and 16 watts.
A wedge base bulb, such as the T15, uses the bulb's glass envelope and wire leads as the electrical contacts, with no separate metal base or pins required for installation.
The Audi S4 uses the 921 bulb for the backup light across the 2009-2016 and 2020-2024 model years.
The 7506 bulb is specified for the 1992-1994, 2000, and 2007-2008 model years of the Audi S4 backup light position.
The 921 and 7506 are not interchangeable without verification, as they differ in base type and electrical characteristics despite both being common automotive bulbs.