Lincoln Mark IV front turn signal bulbs use 1157NA or 1034NA sizes, while rear turn signal bulbs use 1157 size. The replacement chart covers 1972 through 1976 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 IV front turn signal uses two different bulb types across its production run, with the 1034NA fitted in 1972-1973 and 1975, and the 1157NA fitted in 1974 and 1976.
The rear turn signal position uses the 1157 bulb consistently across all model years covered, from 1972 through 1976.
All three bulb types found in these specifications share the BAY15d bayonet base, a double-contact offset-pin base that physically distinguishes dual-filament bulbs from single-filament equivalents.
The 1157NA and 1034NA are both rated at 12V with a 21W/5W dual-filament output, meaning the higher wattage filament activates for the turn signal function while the lower wattage filament serves a secondary role such as parking light operation.
The 1034NA is described as a variant of the 1157, and both the 1034NA and 1157NA share the natural amber glass construction, which produces an amber signal output without relying on an amber lens or housing.
The standard 1157 used in the rear position has the same 12V, 21W/5W rating and BAY15d base as the 1157NA, but its glass is clear rather than natural amber, making the two bulbs visually distinct despite their electrical similarities.
Because the 1034NA is a variant of the 1157 rather than an identical replacement, substituting one for the other in the Lincoln Mark IV front turn signal positions warrants attention to whether the specific variant is required for a given model year.
All bulbs listed in these specifications conform to ANSI standards applicable in both the United States and Canada, indicating they meet a common North American regulatory baseline for automotive lighting.