Mercury Montclair front and rear turn signal bulbs utilize sizes 1157NA, 1034NA, 1034, 1157, and 1154 depending on production specifications. The replacement chart covers 1955 through 1968 model years with corresponding bulb size data.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Mercury Montclair uses the BAY15d bayonet base across all listed turn signal bulb types, spanning both front and rear positions from 1955 through 1968.
Every bulb type specified for the Montclair's turn signals is a dual-filament design, with the higher filament wattage serving the turn signal function and the lower wattage serving a secondary role such as running or parking light.
The 1034 and 1034NA are variants of the 1157, sharing the same BAY15d base and 12V, 21W/5W ratings, which indicates a degree of interchangeability within the 1157 family, though fitment should be confirmed before substitution.
The "NA" suffix on the 1157NA and 1034NA designates natural amber glass, meaning the amber color is built into the bulb itself rather than produced by a colored lens.
The Mercury Montclair (1967-1968) front turn signals use the 1157NA, while the rear turn signals for those same years use the standard 1157, indicating that the front positions require a bulb with natural amber glass while the rear positions do not.
The 1034NA was specified for the Montclair's front turn signals during 1964-1966, again pairing a natural amber bulb at the front with a clear-glass 1157 at the rear.
The 1154 bulb, used on the 1955 Montclair in both front and rear turn signal positions, is rated for 6V or 12V operation, distinguishing it from all other bulbs in these specifications, which are rated strictly at 12V.
From 1956-1960, both the front and rear turn signal positions on the Montclair used the same 1034 bulb, making those model years the only ones in the specifications where front and rear positions share an identical part number.