Audi Q3 front turn signal bulbs use 12174NA or 12174SV sizes, while rear turn signal bulbs use PY21W size. The replacement bulb size chart covers 2015 to 2024 production years.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The 12174NA is an OEM-designated bulb with natural amber glass and a 12V rating. It serves as the front turn signal bulb across the widest range of model years in the Audi Q3 specifications, covering 2015, 2016-2018, 2019-2020, and 2023-2024.
The 12174SV is a Philips SilverVision variant featuring an enhanced coating over a halogen element, also rated at 12V. Within the Audi Q3 front turn signal specifications, it appears exclusively for the 2021 model year, making it a year-specific fitment rather than a general-use replacement.
Because the 12174NA and 12174SV share the same base part number series but differ in glass treatment and coating, they are not confirmed interchangeable within these specifications. The 2021 front position is listed exclusively with the 12174SV designation.
The PY21W follows the ECE lighting standard, which is used across Europe and other international markets. It is a single-filament amber bulb rated at 12V and 21W, fitted with a BAU15s offset bayonet base. The offset pin prevents incorrect installation of a clear or non-amber bulb in an amber-designated socket.
The rear turn signal position on the Audi Q3 uses the PY21W across all listed model years from 2015 through 2024, indicating a consistent rear fitment regardless of front-position variations across the same period.
The front turn signal specifications for 2016-2018 carry a "With HID Headlamps" condition, meaning the 12174NA fitment for those years applies specifically to vehicles equipped with HID headlamps rather than to all configurations of those model years.
The 2019-2020 front turn signal entries carry a "Without Daytime Running Lamps" condition. This indicates the 12174NA fitment for those years is specific to vehicles not equipped with daytime running lamps, reflecting a configuration-dependent fitment.
The BAU15s base on the PY21W is an offset single-contact bayonet fitting. It differs from the more common BA15s base by having asymmetrically placed pins, which physically restricts installation to the correct bulb type and prevents substitution with non-amber single-filament bulbs sharing a standard base.
The front and rear turn signal positions on the Audi Q3 use entirely different bulb families. The front positions draw from the 12174 series, while the rear position uses the ECE-standard PY21W, meaning the two positions are not interchangeable with one another.