The Plymouth Custom front and rear turn signal bulbs both utilize a 1034 bulb size across the model line. The replacement chart covers vehicle production spanning 1958 to 1961.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The 1034 bulb is the sole bulb type specified across all turn signal positions for the Plymouth Custom, covering model years 1958-1961.
The 1034 is an ANSI-standardized bulb recognized in both the United States and Canada, operating at 12 volts with a dual-filament configuration rated at 21/5 watts.
The dual-filament design of the 1034 allows a single bulb to serve two distinct lighting functions, with the higher-wattage filament typically handling the turn signal or brake function and the lower-wattage filament handling a secondary function such as running light duty.
The 1034 uses a BAY15d bayonet base, which is an offset-pin bayonet mount. The two pins are positioned at different heights, which prevents incorrect single-filament bulbs from being seated in the socket.
The 1034 is a variant of the more widely known 1157 bulb. While both share the BAY15d base and dual-filament construction, the 1034 operates at lower wattage than the 1157, making them non-interchangeable despite their physical similarities.
Because the 1034 and 1157 share the same BAY15d base type, a 1157 bulb can physically seat into a 1034 socket. However, the wattage difference means substituting a 1157 for a 1034 may affect circuit load and is outside the stated specification for the Plymouth Custom.
The same 1034 bulb size is specified for both the front and rear turn signal positions across all four model years, indicating a uniform bulb fitment throughout the vehicle for these functions.