The Mercedes-Benz CLK320 front fog light uses a 9006 or H1 bulb size, while the rear fog light requires a P21/4W or P21W bulb size. The replacement chart covers 1998 to 2005 model years with corresponding bulb specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Mercedes-Benz CLK320 front fog lights use two distinct bulb types across the 1998-2005 model years, with H1 fitted from 1998-2002 and 9006 fitted from 2003-2005.
The H1 is an ECE-standard single-filament halogen bulb operating at 12V and 55W, mounted on a P14.5s pin base. It holds approval for use in the US and Japan in addition to European and worldwide markets.
The 9006 is an ANSI-standard single-filament halogen bulb operating at 12V and 55W, mounted on a P22d base. Its standardization is specific to the US and Canada.
Although both the H1 and 9006 share the same 12V/55W electrical rating, their base types differ, making them physically non-interchangeable despite identical power consumption.
The rear fog lights on the CLK320 also split across two bulb types, with P21W fitted from 1998-2002 and P21/4W fitted from 2004-2005.
The P21W is an ECE-standard single-filament signalling bulb rated at 12V and 21W, using a BA15s bayonet base with a single contact offset.
The P21/4W is an ECE-standard dual-filament signalling bulb rated at 12V with filaments at 21W and 4W, using a BAZ15d bayonet base. The BAZ15d base features offset pins to prevent incorrect installation of the dual-filament bulb in a single-filament socket.
The P21W and P21/4W use different bayonet bases, BA15s and BAZ15d respectively, and are not interchangeable despite sharing a 21W primary filament rating.
The year 2003 represents a transition point in the rear fog light specification, where the CLK320 shifted from P21W to P21/4W, indicating a change in rear fog light circuit design between that generation and the next.
All four bulb types across both fog light positions conform to either ECE or ANSI regulatory frameworks, with the H1, P21W, and P21/4W falling under ECE standards and the 9006 falling under ANSI standards.