Mercedes-Benz 300E Back Up Light Bulb Size

The Mercedes-Benz 300E back up light utilizes a P21W bulb size for illumination. Data for the specified component covers the range from 1986 through 1993.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Bulb Size by Year Range

Years	Bulb Size
1986-1993	P21W

Bulb Specifications

Description	Bulb Size
ECE standard (Europe & worldwide). Single-filament signalling bulb with BA15s bayonet base. 12V, 21W.	P21W

Other Locations

Additional Notes

The Mercedes-Benz 300E uses the P21W bulb as the specified back up light bulb size across all listed model years, spanning 1986-1993.
The P21W is an ECE-standard bulb, meaning it conforms to the Economic Commission for Europe regulatory framework, which governs automotive lighting across European and many worldwide markets.
P21W bulbs operate on a 12-volt electrical system and draw 21 watts, which is typical for single-filament signalling applications such as reverse lights.
The P21W uses a BA15s bayonet base, where "BA" denotes a bayonet cap fitting, "15" refers to the 15mm base width, and the lowercase "s" indicates a single contact at the base, distinguishing it from dual-contact variants.
Because the P21W is single-filament, it serves only one lighting function per bulb, which is consistent with its role in a dedicated back up light circuit.
The BA15s base is not interchangeable with the BA15d base, as the latter carries two contacts and is designed for dual-filament bulbs. Substituting a BA15d bulb in a BA15s socket is not electrically compatible.
The uniform P21W fitment across the entire 1986-1993 production span of the 300E indicates a consistent lamp housing design was retained throughout that generation.