The Mercedes-Benz C240 front fog light uses a 9006 bulb size, while rear fog lights require P21W or P21/4W bulb sizes. The replacement chart covers vehicle production years spanning 2001 to 2005 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 C240 uses the 9006 bulb across all front fog light positions for the 2001-2005 model years. This bulb follows the ANSI standard used in the United States and Canada, operates at 12V and 55W, and features a single filament with a P22d base.
The 9006 is a halogen bulb type, meaning it uses a tungsten filament enclosed in a halogen gas environment to produce light. The P22d base is a wedge-style locking connector specific to this bulb family.
The rear fog light position on the C240 uses ECE-standard bulbs across the 2001-2005 model years. The ECE standard governs lighting equipment in Europe and most markets outside North America.
For the 2001-2003 and 2005 rear fog light positions, the specified bulb is the P21W. This is a single-filament signalling bulb rated at 12V and 21W, fitted with a BA15s bayonet base.
The BA15s base on the P21W is a single-contact bayonet fitting. The single-contact design means the bulb carries only one electrical circuit, consistent with its single-filament construction.
The 2004 model year rear fog light on the Mercedes-Benz C240 specifies the P21/4W rather than the P21W. These two bulbs share a similar form but are not interchangeable due to differences in base type and filament configuration.
The P21/4W is a dual-filament bulb rated at 12V with a primary filament at 21W and a secondary filament at 4W. It uses a BAZ15d bayonet base, which is an offset dual-contact fitting designed to prevent incorrect installation.
The BAZ15d base on the P21/4W differs physically from the BA15s base on the P21W. The offset pin placement on the BAZ15d ensures the bulb seats in only one orientation, preventing the two filaments from being connected to the wrong circuits.
Because the P21W and P21/4W use different base types, substituting one for the other in the rear fog light socket is not supported by the specifications. The 2004 model year rear fog light position requires the P21/4W specifically.
The front and rear fog light circuits on the C240 operate on different bulb standards. The front uses an ANSI-classified halogen bulb, while the rear uses ECE-classified signalling bulbs, reflecting a common practice of separating high-output driving illumination from lower-wattage signalling functions.