Mercedes-Benz C320 front fog lights utilize 9006 bulb size while rear fog lights require P21W or P21/4W bulb sizes. The replacement chart covers 2001 through 2005 production years with corresponding bulb size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Mercedes-Benz C320 uses the 9006 bulb for the front fog light across all listed model years, spanning 2001-2005.
The 9006 is an ANSI-standard halogen bulb rated at 12V and 55W, operating on a single filament with a P22d base. Its classification under the ANSI system places it within the North American standardization framework used in the United States and Canada.
The P22d base on the 9006 is a wedge-style connector specific to that bulb family, meaning it is not interchangeable with bayonet-style bases found on ECE-standard signalling bulbs.
The rear fog light on the C320 uses the P21W for model years 2002-2005. This is an ECE-standard single-filament signalling bulb rated at 12V and 21W, fitted with a BA15s bayonet base.
The 2001 C320 rear fog light takes the P21/4W rather than the P21W. The P21/4W is a dual-filament ECE bulb rated at 12V with filaments at 21W and 4W, and it uses a BAZ15d bayonet base.
The BA15s base on the P21W and the BAZ15d base on the P21/4W are physically distinct. The BAZ15d features offset pins to prevent incorrect installation, which means the P21W and P21/4W are not interchangeable despite sharing a similar appearance.
The wattage difference between the front fog light bulb (55W) and the rear fog light bulbs (21W or 21W/4W) reflects their different functional roles, with the higher-wattage halogen unit providing forward illumination and the lower-wattage ECE bulbs serving as signalling lamps.
The coexistence of ANSI-standard bulbs at the front and ECE-standard bulbs at the rear of the C320 indicates a mixed lighting specification across the vehicle's fog light positions.