Ford Transit front inner and front turn signal bulbs utilize 3457NA size, while rear turn signal bulbs use PY21W or 3057 size. The replacement chart covers vehicle production years spanning 2015 to 2023 with corresponding bulb specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The 3457NA is the most frequently specified bulb across the Ford Transit turn signal positions, appearing in the Front Inner Turn Signal for 2015-2020 and the Front Turn Signal for 2017-2018 and 2020-2023.
The 3457NA is an ANSI-standard dual-filament T25 wedge bulb rated at 12V with a 27W high filament and 7W low filament. Its natural amber glass produces the required amber signal color without relying on a colored lens.
The 3057 shares the same T25 wedge form and 12V, 27W/7W dual-filament rating as the 3457NA but lacks the natural amber glass coating, making the two bulbs physically similar yet visually distinct in output.
The Ford Transit (2015-2020) Rear Turn Signal uses the 3057, while the 2023 model year uses the PY21W, reflecting a shift to a different base type and filament configuration for that position.
The PY21W follows the ECE standard used in European and worldwide markets. It is a single-filament amber bulb rated at 12V and 21W, fitted with a BAU15s offset bayonet base, which is not interchangeable with the standard BA15s base found on many other automotive bulbs.
The Ford Transit (2015-2016) Front Turn Signal uses the 12961, designated for the mirror position. This is a miniature T10 wedge bulb with a W2.1x9.5d base, rated at 12V and 5W, a significantly lower wattage than the 3457NA used in other front turn signal positions.
The W2.1x9.5d base of the 12961 is physically incompatible with the T25 wedge base of the 3457NA, meaning the mirror-mounted front turn signal socket on 2015-2016 models does not accept the bulb used in other front signal positions on the same vehicle.
The BAU15s bayonet base of the PY21W features an offset pin arrangement specifically designed to prevent installation of non-amber bulbs in turn signal sockets, distinguishing it from the standard BA15s base used on clear single-filament bulbs of similar wattage.