Ford C-Max front inner turn signal bulbs use 3457NA size, while front turn signals accommodate 3457NA or 2357NA sizes, and rear turn signals require 7440NA bulb size. The replacement chart covers 2013 through 2018 model years with corresponding bulb size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Ford C-Max uses three distinct bulb types across its turn signal positions: the 3457NA, the 2357NA, and the 7440NA, all of which conform to ANSI standards recognized in the United States and Canada.
The 3457NA is the most widely specified bulb across the C-Max turn signal positions, appearing in both the Front Inner Turn Signal and Front Turn Signal locations for the 2013-2018 model years, with one exception in the 2017 Front Turn Signal position.
The 3457NA is a dual-filament wedge bulb in the T25 form factor, rated at 12V with a 27W high filament and a 7W low filament. Its natural amber glass produces the orange-tinted output required for turn signal applications without relying on a colored lens or coating.
The 2357NA is specified exclusively for the 2017 Ford C-Max Front Turn Signal position, where it is noted as a headlight-adjacent fitment. It uses a BAY15d bayonet base rather than a wedge base, which makes it physically incompatible with sockets designed for the 3457NA despite sharing a similar dual-filament configuration and voltage rating.
The BAY15d base of the 2357NA features two offset pins that lock the bulb into a specific rotational orientation, a design that differs fundamentally from the wedge-style retention of the 3457NA and prevents cross-substitution between the two types.
The 7440NA is specified for the Rear Turn Signal position across all model years from 2013-2018. It is a single-filament T20 wedge bulb rated at 12V and 21W, meaning it does not carry a secondary filament for combined stop or parking light functions.
The T20 wedge base of the 7440NA and the T25 wedge base of the 3457NA are physically distinct sizes. Although both use a wedge-style retention method, the difference in base width means the two bulbs are not interchangeable even where socket type might otherwise suggest compatibility.
The natural amber glass construction of all three bulb types (3457NA, 2357NA, and 7440NA) is a defining characteristic of the NA designation. This glass tints the emitted light amber at the source, as opposed to clear-glass variants that depend on an external amber lens to achieve the same effect.
The wattage difference between the 3457NA (27W/7W) and the 2357NA (26.9W/8W) is marginal, but the two bulbs remain non-interchangeable due to their incompatible base designs.
Because the 2017 Front Turn Signal position on the Ford C-Max calls for the 2357NA rather than the 3457NA used in all other years and positions, the base type must be confirmed before a replacement bulb is selected for that specific position and model year.