Chevrolet Caprice Turn Signal Bulb Size

Additional Notes

• The H21W is the front turn signal bulb for the Chevrolet Caprice across the 2011-2017 model years. It follows the ECE standard used in Europe and worldwide markets, operates at 12V with a 21W single-filament output, and uses a BAY9s base. As a single-filament type, it serves only the signalling function rather than combining turn and running light duties in one bulb.
• The 7443 serves as the rear turn signal bulb for the 2011-2017 Caprice. It is a dual-filament T20 wedge bulb rated at 12V with a 21W high filament and 5W low filament, conforming to the ANSI standard used in the US and Canada. The wedge base design differs from the bayonet bases found in earlier model years.
• The 1157 is the most widely used bulb across the rear turn signal positions in the specifications, covering the 1966-1981 and 1973-1982 rear positions. It is a dual-filament BAY15d bayonet bulb rated at 12V, 21W/5W under the ANSI standard. The same base type appears across several related bulb variants used in this vehicle line.
• The NA suffix on bulbs such as 2057NA, 3057NA, 1034NA, and 1157NA denotes natural amber glass. This coloring is built into the glass envelope itself rather than applied through a lens or coating, producing the amber signal color required by regulations without relying on the housing.
• The 2057NA is specified for the front turn signal position on the Caprice from 1983-1990. It shares the BAY15d bayonet base with the 1157 family but operates at higher wattages of 26.9W and 8W across its two filaments, making it a brighter variant within the same base family.
• The 3057NA appears in the front turn signal position for the 1991-1992 Caprice. Unlike the BAY15d bayonet bulbs used in surrounding years, the 3057NA uses a T25 wedge base, meaning it is physically incompatible with sockets designed for the bayonet-style bulbs used in earlier model years despite serving the same function.
• The 1034NA is specified for the front turn signal on the Caprice across multiple non-consecutive years between 1974 and 1982. It uses the BAY15d bayonet base and is rated at 12V with a 21W high filament and 5W low filament, placing it in the same wattage class as the 1157NA despite being a distinct part number.
• The 1157NA and 1157 share identical voltage and wattage ratings of 12V, 21W/5W and the same BAY15d bayonet base. The only distinction is the amber glass envelope on the 1157NA. Because the base and electrical characteristics are the same, the socket fitment is identical between the two variants.
• The rear turn signal position transitions from the 1157 bayonet bulb used through 1982 to the 2057 in 1983, then to the 7443 wedge bulb in 2011. The 2057 and 1157 share the BAY15d base, so those two are socket-compatible, but the 7443 uses a T20 wedge base and is not interchangeable with either of the bayonet-base types.
• The front and rear turn signal positions on the 2011-2017 Caprice use different bulb types, H21W at the front and 7443 at the rear, which are not interchangeable. The H21W follows the ECE standard with a BAY9s base, while the 7443 follows the ANSI standard with a T20 wedge base, and the two differ in base design, filament count, and regulatory standard.