The Mercedes-Benz C240 tail light requires bulb size P21/5W or 12821 depending on the specific application. Data for the provided components covers the range from 2001 to 2005.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Mercedes-Benz C240 outer tail light specifications reference three distinct bulb types across the 2001-2005 model years: P21/5W, P21/4W, and the Philips 12821.
The P21/5W is an ECE-standard dual-filament signalling bulb rated at 12V with a 21W main filament and a 5W secondary filament. It uses a BAY15d bayonet base.
The P21/4W shares the same ECE-standard dual-filament construction and 12V/21W rating as the P21/5W but carries a lower 4W secondary filament. It uses a BAZ15d bayonet base rather than a BAY15d.
The BAY15d and BAZ15d bases are physically distinct. The offset pin positions differ between the two, meaning P21/5W and P21/4W bulbs are not interchangeable despite their similar appearance and wattage ratings.
The Philips 12821 is a miniature wedge-type bulb in the T10 form factor, rated at 12V and 5W, with a W2.1x9.5d base. It is a single-filament bulb, unlike the P21/5W and P21/4W.
The 2001-2002 C240 outer tail light position uses the Philips 12821, while the 2003-2005 model years use either P21/4W or P21/5W depending on the specific sub-position within the outer tail light assembly.
For the 2003-2004 C240, one outer tail light sub-position calls for P21/4W while another calls for P21/5W, indicating the assembly contains sockets requiring two different dual-filament bulb types simultaneously.
The 2005 C240 outer tail light assembly uses P21/5W across both sub-positions, making it the only model year in this specification set where a single dual-filament bulb type covers all listed sockets.