Audi A4 Headlight Bulb Size

Additional Notes

• The H7 bulb is the most frequently specified type across the Audi A4 headlight data, appearing in both high beam and low beam positions across multiple model years and headlamp configurations. It is a halogen bulb with a single filament, operating at 55 watts on a 12-volt system, and uses a PX26d base.
• The D3S bulb is a high-intensity discharge type specified for both high beam and low beam positions on the Audi A4 from 2009-2016. It operates without a mercury compound, uses a three-electrode igniter integrated into the burner, and runs on a high-voltage ballast system rather than a standard 12-volt circuit.
• The D5S bulb is specified for both high beam and low beam positions on the Audi A4 from 2017-2019 with HID headlamps. Like the D3S, it is mercury-free and belongs to the discharge family, but it is not interchangeable with D3S units due to differences in the base and igniter configuration.
• The D1S bulb appears in both high beam and low beam positions for 2007-2008 HID-equipped models, and also in the low beam position for the 2002 model year. It differs from the D3S and D5S types in that its igniter is housed within the ballast rather than integrated into the burner itself.
• The D2S bulb is specified exclusively for the low beam position on 1999-2001 HID-equipped models. It shares the same external igniter design as the D1S but uses a different base, making the two types physically incompatible despite their similar operating principles.
• The H8 bulb is specified for the high beam position on the Audi A4 for 2017-2020, including configurations described as halogen with a gas discharge headlamp system. The H8 is a single-filament halogen type rated at 35 watts, which is notably lower wattage than the H7, and uses a PGJ19-1 base.
• For 2007-2014 model years, the Audi A4 high beam and low beam positions each carry two distinct bulb specifications depending on headlamp type, one for HID-equipped vehicles and one for halogen capsule headlamp vehicles. These specifications are not interchangeable, as HID and halogen systems use fundamentally different operating voltages and socket types.
• The 2019 high beam specification includes a unique notation referencing a gas discharge headlamp with a D5/D7 system alongside an H8 halogen bulb. This indicates the H8 serves as the high beam source within a projector or reflector housing that otherwise uses discharge technology for low beam output.
• The low beam position for 1996-1997 model years carries only the H7 specification with no HID alternative listed, while the 1999-2002 low beam entries include both H7 and discharge options. This reflects the gradual introduction of HID technology as an available headlamp configuration during that period.
• Across the full span of specifications, the high beam and low beam positions share the same bulb type in most HID-equipped years, with D1S, D3S, and D5S each appearing in both positions simultaneously for their respective year ranges. This is characteristic of bi-xenon headlamp systems, which use a single discharge bulb and a mechanical shield to alternate between beam patterns.