Mercury Marquis front turn signal bulbs utilized 1157NA, 1157, or 1034NA sizes, while rear turn signal bulbs used 1157 size bulbs. The replacement chart contains bulb size specifications across 20 model years from 1967 to 1986.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The three bulb types specified across the Mercury Marquis turn signal positions, 1157NA, 1157, and 1034NA, all share the BAY15d bayonet base and dual-filament construction rated at 12V with a 21W/5W output split between the high and low filaments.
The BAY15d base is an offset twin-pin bayonet fitting, where the two pins are positioned at different heights to ensure correct polarity orientation during installation.
The 1157NA and 1034NA designations indicate bulbs with natural amber glass, which produces the amber signal color through the glass itself rather than relying solely on a colored lens.
The 1034NA is classified as a variant of the 1157 within the ANSI standard, meaning it shares the same base type and voltage-wattage rating while differing in its physical envelope characteristics.
Because the 1034NA is a variant rather than a direct equivalent of the 1157, substituting one for the other in front turn signal positions warrants attention to fitment compatibility for the specific model year.
The rear turn signal position on the Mercury Marquis uses the 1157 bulb without variation across all listed years from 1967-1986, making it the most consistent specification in the dataset.
The front turn signal position alternates between 1157NA and 1034NA across different model years, with 1157NA appearing in 1968, 1974, 1976-1977, 1981, and 1983-1986, and 1034NA appearing in 1967, 1969, 1972-1973, 1975, and 1978-1980.
The years 1970 and 1971 are the only front turn signal positions specified with the standard 1157, which lacks the natural amber glass of the 1157NA variant used in surrounding years.
The dual-filament design of all three bulb types serves two functions within a single housing, with the higher 21W filament operating for the active turn signal flash and the lower 5W filament serving as a parking or running light.
All three bulb types conform to ANSI standards recognized in both the United States and Canada, placing them within a standardized North American automotive lighting classification system.