The Jaguar XJ12 front turn signal requires a P21W bulb size while the rear turn signal uses a PY21W bulb size. The replacement chart covers 1973 to 1996 production years with corresponding bulb size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Jaguar XJ12 front turn signal uses two distinct bulb types across its model years: the 1157 for 1973-1979 and the P21W for 1994-1996.
The 1157 is an ANSI-standard dual-filament bulb rated at 12V with a 21W main filament and a 5W secondary filament, mounted on a BAY15d bayonet base.
The BAY15d base on the 1157 features offset pins, which physically prevents it from being substituted with single-filament bulbs that use a BA15s or BAU15s base.
The P21W is an ECE-standard single-filament bulb rated at 12V, 21W, with a BA15s bayonet base, and is used in the front turn signal position on 1994-1996 models.
The rear turn signal on 1973-1979 models takes the 1156, an ANSI-standard single-filament bulb rated at 12V, 21W, also fitted with a BA15s bayonet base.
Although the P21W and 1156 share the same BA15s base type and wattage rating, the P21W follows ECE standards while the 1156 follows ANSI standards, and the two are not guaranteed to be interchangeable across all applications.
The rear turn signal on 1994-1996 Jaguar XJ12 models uses the PY21W, an ECE-standard single-filament amber bulb rated at 12V, 21W, with a BAU15s bayonet base.
The BAU15s base on the PY21W has asymmetrically offset pins, distinguishing it from the BA15s base used on both the P21W and 1156, which makes cross-substitution between these types physically incompatible.
The amber tint of the PY21W is built into the glass envelope itself, meaning the bulb produces a colored output without relying on a tinted lens in the housing.
The shift from ANSI-standard bulbs in the 1973-1979 models to ECE-standard bulbs in the 1994-1996 models reflects a change in the regulatory lighting standards applied to the XJ12 across those production periods.