Subaru Ascent front turn signal bulbs use 1157 or 7444NA sizes, while rear turn signal bulbs use 7444NA or 7440NA sizes. The replacement bulb size chart covers 2019 through 2024 production years.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The 1157 is a dual-filament bulb rated at 12V with a 21W main filament and a 5W secondary filament, mounted on a BAY15d bayonet base. Its two filaments allow it to serve both turn signal and parking light functions within a single housing.
The 7444NA is a dual-filament T20 wedge bulb rated at 12V, 21W/5W, with natural amber glass. The amber coating produces a yellow-orange output without relying on a colored lens, satisfying regulations in markets where clear lenses are used with amber light sources.
The 7440NA shares the T20 wedge form factor and natural amber glass of the 7444NA but carries only a single filament rated at 12V, 21W. This single-filament design limits its function to one circuit, making it unsuitable as a direct replacement for dual-filament applications.
The Subaru Ascent front turn signal uses the 1157 for the 2023-2024 model years and the 7444NA for the 2019-2022 model years. Both bulbs share the same 12V, 21W/5W electrical rating, but their bases differ: the 1157 uses a BAY15d bayonet base while the 7444NA uses a T20 wedge base, making them physically incompatible with each other's sockets.
The rear turn signal of the Subaru Ascent uses the 7444NA for 2024 and the 7440NA for 2019-2023. Although both are T20 wedge bulbs with natural amber glass, the 7444NA has two filaments and the 7440NA has one, which means they are not interchangeable despite sharing the same base type.
All three bulb types listed across these specifications conform to ANSI standards applicable in the United States and Canada, indicating they meet the photometric and dimensional requirements defined for those markets.