The Jaguar XJ6 brake light components utilize P21/5W, P21W, and 1157 bulb sizes depending on the specific production period. The provided technical data covers the range from 1972 through 1997.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Jaguar XJ6 brake light specifications reference two distinct bulb standards across its model range. The 1157 follows the ANSI standard used in the United States and Canada, while the P21W follows the ECE standard common in Europe and worldwide markets.
The 1157 is a dual-filament bulb rated at 12V with a 21W main filament and a 5W secondary filament, mounted on a BAY15d bayonet base. Its dual-filament design allows a single bulb to serve both brake and tail light functions simultaneously.
The P21W is a single-filament bulb rated at 12V, 21W, mounted on a BA15s bayonet base. Because it carries only one filament, it serves a single lighting function, unlike the dual-filament 1157.
Although the 1157 and P21W share the same 21W output on their primary filaments and both use bayonet-style bases, they are not interchangeable. The 1157 uses a BAY15d base with offset pins, while the P21W uses a BA15s base with a single contact, making physical fitment incompatible between the two.
The Jaguar XJ6 brake light used the 1157 bulb for the 1972-1979 model years, switched to the P21W for the 1980-1994 model years, and then returned to the 1157 for the 1995-1997 model years.
The center high mount stop light on the Jaguar XJ6 used the 12961 bulb across the 1984-1997 model years, representing a consistent fitment throughout that entire span.
The 12961 is a Philips part number designating a miniature wedge bulb in the T10 form factor, rated at 12V and 5W, with a W2.1x9.5d wedge base. Its low wattage reflects its role as a supplemental stop light rather than a primary brake signal source.
The wedge base of the 12961 is physically and electrically distinct from the bayonet bases used by both the 1157 and the P21W, meaning none of the three bulb types specified for the XJ6 are interchangeable with one another.