Peugeot 504 front and rear turn signal bulbs utilize a P21W size across all applications. The replacement chart covers vehicle production spanning 1969 to 1983.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Peugeot 504 uses the P21W bulb size for both the front and rear turn signals across the full 1969-1983 production span covered by these specifications.
The P21W is an ECE-standardized bulb type, meaning it conforms to the United Nations Economic Commission for Europe regulations governing automotive lighting components used in Europe and many other markets worldwide.
The P21W operates at 12 volts and draws 21 watts, which is the standard wattage for single-filament turn signal applications in European-market vehicles of this era.
The bulb uses a BA15s bayonet base, where "BA" denotes a bayonet cap fitting, "15" refers to the 15mm base width, and the lowercase "s" indicates a single contact at the base, corresponding to its single-filament construction.
Because the P21W is a single-filament bulb, it serves a dedicated signalling function rather than a combined stop-and-turn function, which would require a dual-filament type such as the P21/5W.
The identical P21W specification across both the front and rear positions means a single bulb type covers all four turn signal housings on the Peugeot 504, with no positional variation in fitment.
The BA15s base is not interchangeable with the BA15d base, which carries two offset contact pins rather than one. Substituting a BA15d bulb into a BA15s socket is not mechanically compatible.
The P21W shares its BA15s base with several other single-filament bulb types that differ in wattage, such as the P5W. Wattage must match the original 21W specification to avoid incorrect flash rates or potential circuit issues in the turn signal system.