The Jaguar Vanden Plas brake light utilizes P21W, P21/5W, and P21/4W bulb sizes depending on the specific version of the vehicle. Data for the lighting components spans from 1982 through 2009.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Jaguar Vanden Plas brake light specifications reference three distinct ECE-standard bulb types across the main brake position: P21W, P21/5W, and P21/4W. Each belongs to the same bayonet-base family but carries different filament configurations and base types, making them physically non-interchangeable despite their similar appearance.
The P21W is a single-filament bulb rated at 12V and 21W, fitted with a BA15s bayonet base. Its single-filament design means it serves one lighting function only, which in this application is braking.
The P21/5W is a dual-filament bulb rated at 12V with filaments drawing 21W and 5W respectively. It uses a BAY15d bayonet base, which offsets the two locating pins at different heights to prevent incorrect installation. This offset-pin design is a deliberate fitment safeguard absent from the single-filament BA15s base used by the P21W.
The P21/4W is also a dual-filament bulb rated at 12V with filaments drawing 21W and 4W respectively. It uses a BAZ15d bayonet base, where the two pins are offset both in height and angular position. This base is distinct from both the BA15s and BAY15d, meaning P21/4W bulbs are not interchangeable with P21W or P21/5W units even though all three share the same 21W primary filament rating.
For the Jaguar Vanden Plas, the main brake position uses the P21W for model years 1982-1994, shifts to P21/5W for 1995-2000, transitions to P21/4W for 2001-2003, returns to P21/5W for 2004-2006, and reverts to P21W for 2007-2009.
Because the base types differ across these three bulb designations, substituting one for another is not mechanically possible without modification to the socket. Each base type is engineered to fit only its corresponding socket configuration.
The Center High Mount Stop Light on the Jaguar Vanden Plas uses the 12961, a Philips-designated miniature wedge bulb. It is classified as a T10 type with a W2.1x9.5d wedge base, rated at 12V and 5W. This base type is entirely different from the bayonet bases used in the main brake position.
The 12961 wedge bulb operates at a significantly lower wattage (5W) than any of the main brake bulbs (21W primary filament). This reflects its role in the center high mount stop light, which typically uses a smaller, lower-output light source than the primary brake assemblies.
The 12961 specification applies to the Center High Mount Stop Light across model years 1984-2008, representing the longest uninterrupted single-bulb specification in these brake light data.
All bulb types referenced in these specifications are 12-volt units, consistent with the standard electrical system voltage used in conventional passenger vehicles of these model years.