Simca 1204 front turn signal bulbs measure 1157 size while rear turn signal bulbs measure P21W size. Replacement chart data spans 1969 to 1971 production years with corresponding bulb specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Simca 1204 uses two distinct turn signal bulb standards across its front and rear positions for the 1969-1971 model years.
The front turn signal on the Simca 1204 takes the 1157 bulb, an ANSI-standard type common in the United States and Canada markets.
The 1157 is a dual-filament bulb operating at 12V with a 21W main filament and a 5W secondary filament, mounted on a BAY15d bayonet base. The offset pins of the BAY15d base prevent incorrect installation by ensuring only one rotational orientation fits the socket.
The rear turn signal across all three model years uses the P21W, an ECE-standard bulb prevalent in European and worldwide markets.
The P21W is a single-filament bulb rated at 12V and 21W, fitted with a BA15s bayonet base. The BA15s base has symmetrical pins, meaning the bulb seats in any rotational position.
The front and rear turn signal bulbs on the Simca 1204 are not interchangeable. The 1157 uses a BAY15d base with offset pins, while the P21W uses a BA15s base with symmetrical pins, making the two physically incompatible with each other's sockets.
The combination of an ANSI-standard front bulb and an ECE-standard rear bulb on the same vehicle reflects a mixed specification that does not conform exclusively to either regulatory framework.