The Audi 90 turn signal requires a bulb size of P21/5W for the lighting system. Data for the specific bulb requirements covers the range from 1995 to 1995.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Audi 90 uses the P21/5W bulb across all listed front turn signal positions for model years 1988-1995, with the exception of 1992, which has no entry in the specifications.
The P21/5W is a dual-filament bulb rated at 12V with a 21W main filament and a 5W secondary filament, mounted on a BAY15d bayonet base.
The BAY15d base features two offset pins, a design that prevents incorrect insertion and distinguishes it from single-filament bayonet bases.
The Audi 90 uses the P21W bulb across all listed rear turn signal positions for model years 1988-1995, with the exception of 1992, which has no entry in the specifications.
The P21W is a single-filament bulb rated at 12V at 21W, mounted on a BA15s bayonet base.
The BA15s base uses a single pin, making it physically incompatible with the dual-pin BAY15d base used by the front turn signal bulb.
Both the P21/5W and P21W conform to ECE standards, meaning they are regulated for use in Europe and other markets that follow ECE lighting regulations.
Although the P21/5W and P21W share the same 21W turn signal filament output, the dual-filament construction of the P21/5W and its BAY15d base make it a non-interchangeable replacement for the single-filament P21W rear turn signal application.