Lincoln Mark III front turn signal bulbs use 1157NA or 1034NA size, while rear turn signal bulbs use 1157 size. The replacement chart covers 1968 through 1971 production years with corresponding bulb size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Lincoln Mark III uses three bulb types across its front and rear turn signal positions: the 1157NA, 1034NA, and 1157, all of which share the BAY15d bayonet base and dual-filament construction rated at 12V with a 21W/5W output split.
The BAY15d bayonet base is a two-pin offset base design, where the offset pin placement ensures correct polarity orientation during installation.
The 21W/5W dual-filament configuration serves two distinct functions within a single bulb housing: the higher 21W filament activates for the turn signal flash, while the lower 5W filament operates as a running or parking light.
The 1157NA carries natural amber glass, which produces an amber-colored output without relying on a colored lens or external filter.
The 1034NA is described as a variant of the 1157 and also features natural amber glass, though it is a distinct ANSI part number and is not interchangeable by designation alone.
The 1157, used across all four model years in the rear turn signal position, does not carry the "NA" amber glass designation, indicating its output color is determined by the vehicle's lens rather than the bulb itself.
The 1969 Lincoln Mark III front turn signal uses the 1034NA rather than the 1157NA specified for the 1968, 1970, and 1971 model years, making 1969 the sole year with a differing front bulb type.
Despite the 1034NA being described as a variant of the 1157, substituting one for the other without confirming fitment compatibility with the specific socket and circuit of the Mark III is not supported by the specifications.
All rear turn signal positions across the 1968-1971 model years share the 1157 bulb, indicating consistent rear fitment throughout the full production run covered by these specifications.
All three bulb types in these specifications conform to ANSI standards applicable in both the United States and Canada.