Audi A3 Back Up Light Bulb Size

Additional Notes

• The Audi A3 backup light bulb specification covers model years 2006-2023 and references two distinct bulb types: the H6W and the 921.
• The H6W is an ECE-standard bulb, meaning it conforms to European and international regulations. It operates at 12 volts and draws 6 watts, making it a low-wattage single-filament signalling bulb. Its base type is BAX9s, a offset pin bayonet base specific to this bulb family.
• The 921 follows the ANSI standard used in the United States and Canada. It is a T15 wedge-base bulb operating at 12 volts and 16 watts, producing notably more wattage than the H6W.
• The Audi A3 uses the H6W for model years 2014-2023, spanning the third and fourth generations of the vehicle.
• Model years 2006-2013 of the Audi A3 use the 921 bulb for the backup light position.
• The BAX9s base of the H6W is not interchangeable with the wedge base of the 921. These two bulb types require physically different sockets, and one cannot be substituted for the other without a socket adapter or wiring modification.
• The wattage difference between the two bulbs is significant. The 921 operates at 16 watts while the H6W operates at 6 watts, a difference that reflects the distinct regulatory and design standards each bulb was developed under.
• Both bulbs share the same operating voltage of 12 volts, which is standard for automotive electrical systems in passenger vehicles.
• The H6W designation is specific to the ECE bulb classification system, while the 921 designation belongs to the ANSI/SAE bulb numbering system used in North American automotive applications.
• Because the 2013 and 2014 model years fall on either side of the bulb type transition, vehicles from those years require verification of the specific bulb type before replacement, as each takes a different socket and wattage rating.