Peugeot 604 front and rear side marker bulbs utilize a 12821 bulb size for both locations. Replacement specifications span a chart covering 1977 to 1984 production years.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Peugeot 604 uses the 12821 bulb across all listed model years, 1977-1984, for both front and rear side marker positions.
The 12821 is a Philips part number designating a miniature wedge bulb of the T10 type, rated at 12 volts and 5 watts.
The T10 designation refers to a tubular bulb form factor approximately 10mm wide, commonly found in low-current automotive marker and interior lighting applications.
The W2.1x9.5d base type is a wedge-style base, meaning the bulb is held in its socket by the tension of the glass envelope itself rather than by a separate metal cap or bayonet fitting.
The "W" prefix in the W2.1x9.5d base designation indicates a wedge base, with 2.1mm and 9.5mm referring to the width and insertion depth of the base respectively.
Because the same bulb number applies to both the front and rear side marker positions across all listed years, a single bulb type services all side marker sockets on the Peugeot 604.
At 5 watts and 12 volts, the 12821 draws approximately 0.42 amperes, which is consistent with the low power demands typical of side marker lighting circuits.
The wedge base of the 12821 is not interchangeable with bayonet-base bulbs such as the BA9s or BAX9s types, despite some overlapping wattage ratings in the T10 size class.