Audi A4 Back Up Light Bulb Size

The Audi A4 back up light bulb uses 921 and 7506 sizes depending on the vehicle production year. The replacement chart covers 1996 to 2020 model years with corresponding bulb size specifications.

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
2009-2020	921
2007-2008	7506
1999-2002	7506
1996-1997	7506

Bulb Specifications

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

Other Locations

Additional Notes

The Audi A4 backup light uses two distinct bulb types across its model years: the 921 and the 7506.
The 921 is the bulb type specified for the Audi A4 from 2009-2020.
The 7506 is the bulb type specified for model years 1996-2002 and 2007-2008.
The 921 bulb follows the ANSI standard, which is the North American standardization system used in the United States and Canada.
The 921 is a T15 wedge-base bulb, meaning it uses a tapering plastic base that presses directly into a socket without a separate metal connector or locking mechanism.
The 921 operates at 12 volts and 16 watts, which is consistent with standard automotive electrical systems.
The T15 designation refers to the bulb envelope width expressed in eighths of an inch, placing the 921 in a relatively compact form factor common in reverse and signal lighting applications.
The 921 and 7506 are not the same bulb type, and the two are not interchangeable without verifying socket and wattage compatibility for the specific model year.