Peugeot 604 front and rear turn signal bulbs use P21W size bulbs for all applications. The replacement chart covers vehicle production spanning 1977 to 1984.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The P21W is the sole bulb type specified for the Peugeot 604 across all listed turn signal positions and model years.
The P21W operates at 12 volts and consumes 21 watts, placing it in the standard single-filament category used for dedicated signalling functions.
The P21W uses a BA15s bayonet base, which is a single-contact bayonet fitting with a 15mm collar. The "s" designation indicates a single contact pin, distinguishing it from the dual-contact BA15d variant.
The P21W is rated under the ECE standard, meaning it conforms to the Economic Commission for Europe's regulations for automotive lighting, a specification recognized across European and many worldwide markets.
Both the front and rear turn signal positions on the Peugeot 604 share the same P21W specification across the 1977-1984 model years listed, indicating a uniform bulb fitment throughout the vehicle's signalling circuit.
Because the BA15s base is a single-contact design, it is not interchangeable with BA15d bulbs, which carry two offset contact pins. Substituting a BA15d bulb in a BA15s socket is not mechanically compatible.
The single-filament construction of the P21W means the bulb serves one function only. It is not a dual-purpose unit and cannot replicate the behavior of twin-filament bulbs such as the P21/5W, which combines turn signal and parking light duties in a single envelope.