The Avanti II front turn signal bulb uses either 1034NA or 1157NA size, while the rear turn signal bulb uses 1157 size. The replacement chart contains vehicle production years and bulb size specifications spanning 1965 to 1973.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Avanti II front turn signal specifications cover model years 1965-1973 and reference two bulb types: the 1034NA and the 1157NA.
The 1157NA and 1034NA are both ANSI-standard dual-filament bulbs rated at 12V, 21W/5W, and both use a BAY15d bayonet base. The 1034NA is described as a variant of the 1157NA.
Both the 1034NA and 1157NA feature natural amber glass, which produces the amber signal color without requiring a colored lens or housing filter.
The dual-filament design in these bulbs serves two functions within a single unit: the higher-wattage filament (21W) operates for the active turn signal flash, while the lower-wattage filament (5W) serves as a parking or running light.
The BAY15d bayonet base is a double-contact base with offset pins, a design that prevents incorrect installation by ensuring the bulb can only be seated in one orientation, which is critical for maintaining correct filament-to-circuit alignment.
The Avanti II rear turn signal uses the 1157 across all model years 1965-1973. Unlike the 1034NA and 1157NA, the 1157 has a clear glass envelope rather than natural amber glass.
The front turn signal of the Avanti II alternates between the 1034NA and 1157NA across different model years, indicating that the two bulbs were used interchangeably in this application despite the 1034NA being classified as a variant of the 1157.
Because the 1034NA, 1157NA, and 1157 all share the BAY15d base and the same 12V/21W/5W ratings, they are electrically and physically compatible with one another, though substituting a clear 1157 in a position specified for an NA-suffix bulb would affect the color output if the lens itself is not amber-tinted.