Mercury Comet front and rear turn signal bulbs utilize 1034NA, 1157NA, and 1157 bulb sizes depending on location and model variant. The replacement chart covers 1960 through 1977 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 1157 bulb is the most widely used type across the Mercury Comet's turn signal specifications, appearing in both front and rear positions across the majority of model years covered.
All four bulb types listed in these specifications, the 1034, 1034NA, 1157, and 1157NA, share the same BAY15d bayonet base and dual-filament design, operating at 12V with a 21W/5W output rating.
The BAY15d base is an offset twin-pin bayonet fitting. The two pins are positioned at different heights, which prevents incorrect single-filament bulbs from being seated in a dual-filament socket.
The 1034 and 1034NA are classified as variants of the 1157, meaning they share the same base type and wattage but are distinct ANSI part numbers.
The "NA" suffix on the 1034NA and 1157NA designates natural amber glass, meaning the amber color is built into the bulb itself rather than produced by a colored lens or housing.
For the Mercury Comet, the front turn signal used the 1157NA in 1976 and in 1968-1969, indicating an amber-glass bulb was specified for those years while clear-glass 1157 bulbs were used in the front position from 1971-1975.
The front turn signal used the 1034NA in 1977 and in 1964-1967, while the clear-glass 1034 was specified for 1960-1962, reflecting a shift in amber-glass requirements at different points in the model's production span.
The rear turn signal used the 1034 in 1960-1962 and transitioned to the 1157 from 1963 onward through 1977, with no NA-suffix bulbs specified for the rear position in any year.
Because the 1034 and 1157 share the BAY15d base, physical fitment between them is possible, but they carry different ANSI part numbers and should not be treated as direct substitutes without confirming the application's requirements.
The year 1970 is absent from both the front and rear turn signal listings for the Mercury Comet in these specifications.