The Austin Marina front turn signal uses a 1156 bulb size while the rear turn signal requires a 1157 bulb size. This replacement chart covers vehicle production spanning 1973 to 1975.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Austin Marina uses two distinct bulb types across its turn signal system for the 1973-1975 model years: the 1156 at the front and the 1157 at the rear.
The 1156 is a single-filament bulb operating at 12V and 21W, fitted with a BA15s bayonet base, and classified under the ANSI standard applicable to the US and Canada.
The 1157 is a dual-filament bulb rated at 12V with a primary filament of 21W and a secondary filament of 5W, mounted on a BAY15d bayonet base, also under the same ANSI standard.
The dual-filament design of the 1157 allows the rear turn signal to serve two electrical functions from a single bulb, which is why its wattage is expressed as two separate values.
The BA15s base of the 1156 and the BAY15d base of the 1157 are not interchangeable. The BAY15d base features offset locating pins to prevent incorrect installation, while the BA15s base has a single contact and symmetrical pins.
Because the 1156 and 1157 share the same 15mm bayonet collar size, physical fitment into a similarly sized socket may be possible, but the differing pin configurations and filament counts make substitution between the two electrically incompatible for the Austin Marina's turn signal circuits.