Mercedes-Benz CLK430 front fog light uses H1 bulb size while rear fog light requires P21W bulb size. Replacement chart covers 1999 to 2003 vehicle 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 CLK430 uses the H1 bulb for the front fog light position across the 1999-2003 model years.
The H1 is a single-filament halogen bulb operating at 12V and 55W, fitted with a P14.5s base, and classified under the ECE standard, which applies across Europe and worldwide markets.
The H1 also carries approval for use in the United States and Japan, reflecting its acceptance beyond ECE-regulated regions.
The rear fog light position on the CLK430 uses the P21W bulb across the 1999-2003 model years.
The P21W is a single-filament signalling bulb rated at 12V and 21W, fitted with a BA15s bayonet base, and also governed by the ECE standard.
The BA15s base on the P21W is a single-contact bayonet fitting, which is not interchangeable with dual-contact bayonet variants such as the BA15d, despite sharing the same physical locking style.
The H1 and P21W serve distinct functions within the CLK430's lighting system, with the H1 designated for forward illumination in fog conditions and the P21W designated for rear signalling in reduced visibility.
Both bulbs operate on a 12V electrical system, consistent with standard automotive voltage, though their wattage ratings differ substantially, with the H1 drawing 55W against the P21W's 21W.