Lincoln Mark V front turn signal bulbs use 1157NA or 1034NA sizes, while rear turn signal bulbs use 1157 size. The replacement chart covers 1977 through 1979 production years with corresponding bulb specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
All three bulb types specified for the Lincoln Mark V, the 1157NA, 1034NA, and 1157, share the BAY15d bayonet base and operate at 12V with a 21W/5W dual-filament configuration.
The BAY15d base is a double-contact bayonet fitting with offset pins, a design that physically prevents incorrect single-filament bulbs from being seated in dual-filament sockets.
The dual-filament construction in all three bulb types serves two circuits within a single housing, with the higher 21W filament handling the turn signal function and the lower 5W filament serving as a running or parking light.
The 1157NA and 1034NA designations both carry the "NA" suffix, which indicates natural amber glass rather than a clear envelope, meaning the amber color is produced by the glass itself rather than by a colored lens or coating.
The 1034NA is described as a variant of the 1157, sharing the same BAY15d base and 12V/21W/5W ratings, which places it in the same functional category despite carrying a different ANSI designation.
For the Lincoln Mark V, the front turn signal position uses the 1157NA for the 1978-1979 model years, while the 1977 model year uses the 1034NA in that same position.
The rear turn signal position on the Lincoln Mark V uses the 1157 across all three model years covered, 1977-1979, with no variation between years.
The 1157 specified for the rear position differs from the front-position 1157NA in that it lacks the natural amber glass, making the lens or housing responsible for any amber output at the rear rather than the bulb itself.
Although the 1034NA and 1157NA share physical and electrical characteristics, substituting one for the other in the front turn signal position of the Lincoln Mark V would involve a change in ANSI designation, and fitment should follow the year-specific specification rather than treating them as freely interchangeable.
All bulb types listed are built to the ANSI standard applicable in both the United States and Canada, indicating a standardized specification rather than a proprietary or market-exclusive part.