Mercedes-Benz 500SEC Back Up Light Bulb Size

The Mercedes-Benz 500SEC back up light requires a P21W bulb size for proper installation and function. Data for the specific bulb size covers the range from 1984 to 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
1993	P21W
1984-1985	P21W

Bulb Specifications

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

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Additional Notes

The P21W is the sole bulb type listed across all recorded model years of the Mercedes-Benz 500SEC for the back up light position.
The P21W operates at 12 volts with a 21-watt single-filament design, classifying it as a signalling bulb rather than an illumination bulb.
The BA15s bayonet base is a single-contact fitting, which distinguishes it from the dual-contact BA15d base used in some other automotive applications. The two are not interchangeable.
The P21W is governed by ECE (Economic Commission for Europe) standards, giving it broad acceptance across European and worldwide markets.
The 500SEC carries this specification across the 1984-1985 model years as well as the 1993 model year.