Audi TT RS Quattro Headlight Bulb Size

Additional Notes

• The H8 bulb is a single-filament halogen type rated at 12V and 35W, operating on a PGJ19-1 base under the ECE standard. It serves as the high beam bulb in the Audi TT RS Quattro across the 2018-2021 model years, with the 2019 entry noting compatibility with both halogen and gas discharge headlamp systems of the D5/D7 type.
• The D1S is an HID (xenon) discharge bulb rated at 85V and 35W, distinguished by a PK32d-2 base and an integral ignitor built into the bulb body. It is designed specifically for projector-type housings and is not interchangeable with reflector-style housings.
• The D5S is a low-voltage compact HID (xenon) type rated at 12V and 25W, using a PK32d-7 base. Its lower operating voltage sets it apart from the D1S, and the two bulbs use different base configurations, making them non-interchangeable despite both being HID discharge types.
• The H7 bulb is a single-filament halogen type rated at 12V and 55W on a PX26d base. At 55W, it draws significantly more power than the H8, and the differing base types mean the two halogen bulbs are not physically interchangeable.
• In the 2012 Audi TT RS Quattro, both the high beam and low beam positions carry dual fitment entries. The D1S applies to vehicles equipped with HID headlamps, while the H7 applies to those fitted with halogen capsule headlamps. The correct bulb depends on which headlamp system the vehicle was built with.
• The D1S appears in the high beam position for the 2012-2013 model years and in the low beam position for the same years, indicating that both beam functions used the same HID bulb type in those configurations.
• From 2018 onward, the high beam position shifted to the H8 halogen bulb, while the low beam for 2021 uses the D5S HID type. This means the two beam positions in the 2021 model year operate on fundamentally different technologies and voltage requirements.
• All four bulb types listed across these specifications conform to the ECE standard, which governs lighting equipment in Europe and most international markets. The H7 and H8 halogen types also carry approval for use in the United States, and the H7 is additionally approved in Japan.
• The integral ignitor on the D1S bulb means the high-voltage starting circuit is housed within the bulb itself, unlike some other HID types where the ignitor is a separate external component. This affects replacement procedure and parts sourcing for the 2012-2013 high and low beam positions.
• The PK32d-7 base of the D5S and the PK32d-2 base of the D1S share a similar designation prefix but are distinct socket types. A D1S bulb cannot be seated in a D5S housing, and vice versa, despite both being HID discharge bulbs within the same general family.