Plymouth Road Runner front turn signal bulbs utilized 1157NA, 1157, or 1034 size specifications, while rear turn signal bulbs used 1157 or 1034 size configurations. The replacement chart covers vehicle production years spanning 1968 to 1975 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 Plymouth Road Runner uses two bulb types across its turn signal positions: the 1157 and its variants (1157NA and 1034), all of which share the dual-filament BAY15d bayonet base and operate at 12V with a 21W/5W power rating.
The BAY15d bayonet base is a two-pin offset base design, where the two pins are positioned at different heights to ensure correct polarity orientation during installation.
The 1157 is the most widely used bulb across the Road Runner's turn signal specifications, appearing in both the front and rear positions for the 1969-1975 model years, with the exception of the front turn signal in 1974-1975.
The front turn signal for the Plymouth Road Runner (1974-1975) uses the 1157NA rather than the standard 1157, while the rear turn signal for those same years retains the 1157.
The 1157NA differs from the 1157 solely in its natural amber glass coating, which produces an amber-colored output without the need for an amber lens.
The 1034 is specified for both the front and rear turn signals on the 1968 Plymouth Road Runner, and while it shares the BAY15d base and the same voltage and wattage ratings as the 1157, it is classified as a variant rather than a direct equivalent.
Because the 1034 is a variant of the 1157 rather than an identical replacement, substituting one for the other without confirming fitment compatibility may not be appropriate for the 1968 model year.
The dual-filament design of all three bulb types serves two functions within a single housing: the higher-wattage 21W filament operates for turn signal and brake functions, while the lower-wattage 5W filament serves as a running or parking light.