Chevrolet Bel Air Turn Signal Bulb Size

Additional Notes

• The 1157 bulb is the most widely used type across the Chevrolet Bel Air turn signal specifications, appearing in both front and rear positions across model years 1964-1975 with the exception of the 1975 front position. It is a dual-filament bulb with a BAY15d bayonet base, rated at 12V and 21W/5W, and meets the ANSI standard for the US and Canada.
• The BAY15d bayonet base is shared by all five bulb types listed in these specifications, namely the 1034, 1034NA, 1154, 1157, and 1157NA. This base type uses an offset double-contact design to ensure correct filament orientation during installation.
• The 1034 and 1034NA are both described as variants of the 1157. The 1034 shares the same 12V and 21/5W rating as the 1034NA, with the NA suffix indicating natural amber glass rather than a clear envelope. Both types use the same BAY15d base.
• The 1157NA, used in the 1974 Chevrolet Bel Air front turn signal position, differs from the standard 1157 only in its natural amber glass construction. The amber coloring is built into the glass itself rather than applied as a coating, which affects the color output of the bulb.
• The 1154 bulb, fitted to the front and rear turn signal positions on the Bel Air for model years 1950-1954, is described as an older variant of the 1157. Unlike the other bulb types in these specifications, the 1154 carries a dual voltage rating of 6V/12V, reflecting the transition period in automotive electrical systems when 6-volt systems were still in use.
• The front and rear turn signal positions share identical bulb specifications across all model years covered, with the sole exception of the 1975 model year, where the front position uses the 1034NA and the rear position uses the 1157.
• Because the 1034, 1034NA, 1157, and 1157NA are all variants sharing the BAY15d base and similar wattage ratings, physical fitment across these types is possible. However, substituting a clear-glass bulb such as the 1157 in a position specified for an NA-suffix amber bulb would alter the color output at the lens.
• The 1154, while sharing the BAY15d base with the other bulb types, carries a different voltage specification and is described as an older variant. Its use in positions later occupied by 12V-only bulbs reflects the electrical system standards of the early 1950s rather than a direct interchangeability with the 1034 or 1157 families.