Audi V8 Quattro Back Up Light Bulb Size

The Audi V8 Quattro back up light uses a P21W bulb size for the rear lighting assembly. Data for the specific bulb requirements covers the range from 1990 to 1994.

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
1990-1994	P21W

Bulb Specifications

Description	Bulb Size
ECE standard (Europe & worldwide). Single-filament signalling bulb with BA15s bayonet base. 12V, 21W.	P21W

Other Locations

Additional Notes

The Audi V8 Quattro uses the P21W bulb for the back up light position across all documented model years, spanning 1990-1994.
The P21W is an ECE-standardized bulb type, meaning it conforms to European and international automotive lighting regulations rather than SAE standards used in North American specifications.
P21W bulbs operate at 12 volts with a 21-watt output, which is a wattage typical of single-filament signalling applications such as reverse and turn signal functions.
The single-filament design of the P21W distinguishes it from dual-filament variants like the P21/5W, meaning it serves only one lighting function per socket.
The P21W uses a BA15s bayonet base, where "BA15" denotes the 15mm bayonet cap and "s" indicates a single contact at the base, as opposed to the BA15d double-contact variant.
The BA15s base type is not interchangeable with BA15d sockets due to the differing contact configurations, which is a relevant fitment consideration when sourcing replacement bulbs for the Audi V8 Quattro.