Rolls-Royce Silver Shadow Back Up Light Bulb Size

The Rolls-Royce Silver Shadow back up light uses bulb size P21W or 1159 depending on the specific application for the vehicle. Information provided covers the range from 1970 through 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
1976	P21W
1975	1159
1970-1974	P21W

Bulb Specifications

Description	Bulb Size
ECE standard (Europe & worldwide). Single-filament signalling bulb with BA15s bayonet base. 12V, 21W.	P21W
ANSI standard (US & Canada). Dual-filament bulb with BAY15d bayonet base. 12V.	1159

Other Locations

Additional Notes

The P21W is the predominant back up light bulb type across the Rolls-Royce Silver Shadow specifications, appearing in six of the seven model years listed.
The P21W follows the ECE standard, which governs vehicle lighting regulations across Europe and much of the world outside North America.
As a single-filament bulb, the P21W is rated at 12 volts and 21 watts, with a BA15s bayonet base featuring a single locating pin on its collar.
The 1975 Rolls-Royce Silver Shadow departs from the surrounding model years by specifying the 1159 bulb rather than the P21W.
The 1159 follows the ANSI standard, which applies to the United States and Canada, distinguishing it from the ECE-governed P21W used in the other years.
Unlike the single-filament P21W, the 1159 is a dual-filament bulb, which means it contains two separate filaments within one envelope to serve more than one lighting function.
The 1159 uses a BAY15d bayonet base, which has two offset locating pins rather than the single pin of the BA15s base used by the P21W, making the two bulb types physically non-interchangeable.
The difference in base design between the P21W and the 1159 means a direct substitution between the two is not possible without modification to the socket.