Ford Festiva front turn signal requires a 1157 bulb size, while rear turn signal applications use either 1156 or 1157 bulb sizes across multiple model generations. The replacement chart covers 1988 through 1993 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 Ford Festiva uses the 1157 bulb for the front turn signal across all model years in the specifications, covering 1988-1993.
The 1157 is a dual-filament bulb operating at 12V with a 21W/5W output and a BAY15d bayonet base, conforming to ANSI standards applicable in the US and Canada.
The dual-filament design of the 1157 allows it to serve two lighting functions from a single socket, which is why it appears in front turn signal positions where combined signaling and parking light duties are common.
The Ford Festiva rear turn signal uses the 1157 bulb for the 1988-1989 model years, then transitions to the 1156 for 1990-1993.
The 1156 is a single-filament bulb operating at 12V with a 21W output and a BA15s bayonet base, also conforming to ANSI standards for the US and Canada.
Although the 1157 and 1156 share a similar physical bayonet base style, the BAY15d base of the 1157 has two offset pins, while the BA15s base of the 1156 has a single pin, making the two bulbs non-interchangeable despite their visual similarity.
Installing a 1157 in a socket designed for a 1156 is not possible without modification, as the pin configurations differ and the socket will not accept the wrong base type.
The wattage ratings of the 1157 and 1156 differ in function: the 1157 draws 21W on its primary filament and 5W on its secondary, while the 1156 draws a fixed 21W with no secondary filament.