Rolls-Royce Silver Wraith II Back Up Light Bulb Size

The Rolls-Royce Silver Wraith II back up light uses bulb size 1159 or P21W depending on the specific production requirements for the vehicle. Data for the lighting components covers the range from 1977 to 1980.

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
1979-1980	P21W
1978	1159
1977	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 Rolls-Royce Silver Wraith II uses two distinct bulb standards across its 1977-1980 model years for the back up light position: the P21W, which follows ECE standards used in Europe and worldwide markets, and the 1159, which follows ANSI standards used in North America.
The P21W is specified for the 1977, 1979, and 1980 model years. It operates at 12 volts with a 21-watt output and uses a BA15s bayonet base, which is a single-contact fitting.
The 1159 is specified exclusively for the 1978 model year. It also operates at 12 volts and uses a BAY15d bayonet base, which is a dual-contact fitting designed to accommodate a dual-filament configuration.
The BA15s base of the P21W and the BAY15d base of the 1159 are not interchangeable. The BAY15d base features two offset pins to prevent incorrect installation, while the BA15s base carries only a single contact pin, making the two physically incompatible.
The P21W is a single-filament bulb, meaning it serves one lighting function per unit. The 1159, by contrast, carries dual filaments, which allows it to serve two independent lighting functions within a single housing.
The shift from P21W in 1977 to the 1159 in 1978, and back to P21W in 1979-1980, indicates that the Silver Wraith II's back up light socket specification was not uniform across its production run, and the correct bulb type is year-specific.