The Mercedes-Benz C230 tail light utilizes bulb sizes P21/5W, 12821, and P21/4W according to the provided specifications for the rear lighting components. Data for the specific bulb sizes covers the range from 1997 through 2007.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The outer tail light positions on the Mercedes-Benz C230 use two distinct ECE-standard dual-filament bulb types across the model's production span: P21/5W and P21/4W.
The P21/5W is a dual-filament signalling bulb operating at 12V with a 21W main filament and a 5W secondary filament, mounted on a BAY15d bayonet base.
The P21/4W shares the same 12V, dual-filament construction but carries a lower-output 4W secondary filament and uses a BAZ15d bayonet base rather than the BAY15d found on the P21/5W.
The BAY15d and BAZ15d bases are not interchangeable. Although both are bayonet-type fittings, their pin offsets differ, which prevents incorrect installation between P21/5W and P21/4W bulbs.
One outer tail light position on the C230 used the Philips 12821, a miniature wedge bulb in the T10 form factor with a W2.1x9.5d base, rated at 12V and 5W. This is a single-filament wedge type and is not interchangeable with either the P21/5W or P21/4W.
The C230 outer tail light specifications show two separate position entries per model year in several cases, indicating that more than one bulb socket exists within the outer tail light assembly.
For the 2005-2007 model years, both outer tail light positions use the P21/5W, making the assembly consistent across its sockets for those years.
For the 2002-2004 model years, one outer tail light position uses the P21/4W while the other uses the P21/5W, meaning the two sockets within the same assembly require different bulb types during that period.
The 1997 and 2002 model years each include the Philips 12821 in one of the outer tail light positions, pairing a single-filament wedge bulb alongside a dual-filament bayonet type within the same assembly.
The 1998-2000 model years specify the P21/4W for one outer tail light position, consistent with the BAZ15d bayonet base used across other years that carry that bulb type.