Mercedes-Benz 280S Map Light Bulb Size

The Mercedes-Benz 280S map light uses bulb sizes 3893 and 12821 depending on the specific production period. Available data for the lighting components covers the range from 1968 to 1976.

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
1975-1976	3893
1968-1971	12821

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Dual-filament bulb with BAY15d bayonet base, specialty application. 12V.	3893
Philips part number. Miniature wedge bulb (T10) with W2.1x9.5d base. 12V, 5W.	12821

Other Locations

Additional Notes

The Mercedes-Benz 280S map light specifications cover model years 1968-1976, with two distinct bulb types used across that span.
The 3893 is an ANSI-standardized bulb recognized in both the United States and Canada, operating at 12 volts with a BAY15d bayonet base and a dual-filament design.
A dual-filament construction means the 3893 contains two separate filaments within a single envelope, each serving an independent circuit function.
The BAY15d bayonet base features offset pins, which physically prevents incorrect insertion of a single-filament substitute into a dual-filament socket.
The 12821 is a Philips part number designation for a miniature wedge bulb of the T10 form factor, rated at 12 volts and 5 watts with a W2.1x9.5d base.
The W2.1x9.5d base is a wedge-type fitting that relies on the bulb's glass envelope pressing directly into the socket, with no separate metal base or locking mechanism.
The 280S used the 12821 for model years 1968-1971 and transitioned to the 3893 for model years 1975-1976, reflecting a change in map light socket design between those periods.
The 3893 and 12821 use fundamentally different base types, a bayonet fitting versus a wedge fitting, making them physically incompatible with each other's sockets.