Subaru Forester Turn Signal Bulb Size

Additional Notes

• The 7440NA bulb is the most widely used type across the Subaru Forester's turn signal specifications, appearing in the front position from 2003-2024 (excluding 2017-2021) and in the rear position from 2001-2024 (excluding 1999-2000). It is a single-filament T20 wedge bulb rated at 12V and 21W, with natural amber glass that produces the amber color required for turn signals without relying on a tinted housing.
• The "NA" suffix found on several bulb types in these specifications, including the 7440NA, 7443NA, 7444NA, 1157NA, and 1034NA, denotes natural amber glass coloring. This distinguishes them from their clear-glass counterparts, which carry the same base number without the suffix.
• The 7443NA and 7444NA bulbs used in the front turn signal position for 2017-2020 are dual-filament T20 wedge bulbs, rated at 12V with a 21W main filament and a 5W secondary filament. This dual-filament configuration differs from the single-filament 7440NA and indicates those positions served a combined function, such as turn signal and parking light.
• The 2021 front turn signal uses a 921 bulb, a single-filament T15 wedge type rated at 12V and 16W. This is a physically smaller wedge format than the T20 family used in surrounding model years, meaning the 921 is not interchangeable with T20 bulbs despite sharing a wedge base style.
• The 1157 bulb specified for the 2023-2024 Subaru Forester front turn signal is a dual-filament bulb with a BAY15d bayonet base, rated at 12V, 21W/5W. Unlike the 1157NA variant used in earlier years, the standard 1157 has clear glass, which means the amber color in those applications is produced by the lens or housing rather than the bulb itself.
• The 1034NA, used in the front turn signal position for 1999 and 2001, is described as a variant of the 1157 and shares the same BAY15d bayonet base and 12V, 21W/5W ratings. Despite this similarity, the two types are not confirmed as interchangeable within these specifications, and substituting one for the other without verifying socket and housing compatibility is not supported by the data provided.
• The rear turn signal for 1998-2000 uses the 1156 bulb, a single-filament type with a BA15s bayonet base rated at 12V and 21W. The BA15s base is a single-contact bayonet fitting, which is physically distinct from the BAY15d dual-contact base used on 1157-family bulbs, making these two base types mutually incompatible.
• A base-type change occurs in the rear turn signal between the 2000 and 2001 model years, where the specification shifts from the 1156 bayonet-base bulb to the 7440NA wedge-base bulb. These two bulb types use entirely different mounting systems and are not interchangeable.