The Audi A4 brake components utilize P21W and P21/5W bulb sizes for various lighting applications across the different production versions listed in the provided data set. Available information covers a specific range of time starting from 1996 and ending in 2020.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The P21W is the most widely used brake bulb type across the Audi A4 specifications listed, appearing across model years 2007-2008 and 2009-2020. It follows the ECE standard used in Europe and worldwide, operates at 12V with a 21W output, uses a single filament, and fits a BA15s bayonet base.
The P21/5W is the brake bulb type specified for the Audi A4 across model years 1996-2002 (excluding 1998 and 2003-2006). Unlike the P21W, it carries a dual filament rated at 21W and 5W respectively, uses a BAY15d bayonet base, and also follows the ECE standard at 12V.
The BA15s base of the P21W and the BAY15d base of the P21/5W are physically distinct. The BAY15d base has two offset locating pins to prevent incorrect installation, while the BA15s has a single pin. These two bulb types are not interchangeable despite their similar appearance.
The 2015 Audi A4 brake bulb specification carries the qualifier "For Vehicle With LED Taillights," indicating that the P21W fitment applies only to a specific taillight configuration on that model year.
For model years 2009-2014, the P21W specification is qualified with "With Halogen Capsule Headlamps," indicating a conditional fitment tied to the headlamp type rather than a universal application across all configurations of those years.
The Center High Mount Stop Light on the Audi A4 uses different bulb types depending on the model year. The 2723 bulb, an ANSI-standard T5 miniature wedge type rated at 12V and 1.4W, is specified for 2000-2001, while the 12961, a T10 miniature wedge bulb with a W2.1x9.5d base rated at 12V and 5W, is specified for 1996-1997 and 1999.
The 2723 and 12961 are not interchangeable. The 2723 is a T5 wedge bulb rated at 1.4W, while the 12961 is a larger T10 wedge bulb rated at 5W with a W2.1x9.5d base, and the two differ in both physical size and wattage output.
The 12961 is identified in the specifications by a Philips part number rather than an ANSI or ECE designation, which distinguishes it from the standardized naming conventions used for the other bulb types listed.