Audi A6 Turn Signal Bulb Size

Additional Notes

• The PSY24W bulb follows the ECE standard and uses a PG20-4 base, which is physically distinct from the BAY15d and BAU15s bayonet bases found on other bulbs in these specifications. This base difference makes PSY24W bulbs non-interchangeable with any other type listed for the Audi A6.
• The 7506 and 7507 bulbs appear across multiple positions and model years in these specifications, though their technical descriptions are not provided in the supplied data.
• Several bulbs in these specifications carry an "NA" suffix, denoting natural amber glass coloring. This includes the 3457NA, 3357NA, 2357NA, 3757NA, and 1157NA types, all of which meet ANSI standards applicable to the US and Canadian markets.
• The 1157 and 1157NA share the same BAY15d bayonet base and dual-filament 12V, 21W/5W ratings. The sole difference is that the 1157NA incorporates natural amber glass, while the 1157 uses clear glass. The Audi A6 front turn signal transitions from the clear 1157 to the amber 1157NA starting with the 1998 model year from VIN 4B-W-000 001.
• The 2357NA and 1157NA both use the BAY15d bayonet base but carry different wattage ratings. The 2357NA operates at 26.9W/8W, while the 1157NA operates at 21W/5W. Both are dual-filament bulbs, and their differing wattage outputs make them functionally distinct despite the shared base type.
• The PY21W uses a BAU15s base, which has an offset pin arrangement that differs from the straight-pin BAY15d base used by the 1157, 1157NA, and 2357NA bulbs. This offset prevents accidental cross-installation between PY21W and BAY15d-based bulbs.
• For the Audi A6 front turn signal in 2012-2014, the required bulb type depends on the headlamp configuration. Both halogen capsule and HID headlamp variants specify the PSY24W, meaning the bulb size itself does not differ between those two configurations for those years.
• The 1996 Audi A6 rear turn signal has two distinct specifications depending on production timing. Early model units use the 1157, while late model units use the 7506, indicating a mid-year change in the rear turn signal assembly.
• The 3457NA is a dual-filament bulb rated at 27W/7W, while the 3357NA is a single-filament bulb rated at 27W. Both use a T25 wedge form factor with natural amber glass, but their filament count differs, making them non-interchangeable in sockets designed for dual-filament operation.
• The front turn signal position on the 2002 Audi A6 specifies the 3757NA, which is a dual-filament T25 wedge bulb. The surrounding model years for that same position specify the 1157NA, which uses a BAY15d bayonet base, indicating a base-type change specific to the 2002 model year in that position.