Jaguar XJ8 License Plate Bulb Size

Additional Notes

• The Jaguar XJ8 license plate position uses two distinct bulb types across its production span, with the DE3423 festoon bulb fitted to 1998-2003 model years and the 12961 wedge bulb fitted to 2004-2009 model years.
• The 12961 is a Philips-designated part number rather than an ANSI industry standard, which means sourcing equivalent replacements requires cross-referencing the T10 wedge form factor and W2.1x9.5d base specification.
• The T10 designation of the 12961 refers to a tubular bulb with a 10/8-inch body width, and the W2.1x9.5d base describes a wedge-type connection where the glass envelope itself acts as the retention and contact mechanism, with no separate metal base pins.
• The 12961 operates at 12 volts and 5 watts, which is a standard low-wattage output typical of license plate illumination applications.
• The DE3423 carries ANSI standardization recognized in both the United States and Canada, meaning the specification is defined by an independent standards body rather than a single manufacturer.
• The DE3423 is a festoon-type bulb measuring 41mm in length, with electrical contact made through metal end caps at each tip of the cylindrical body rather than through a wedge base or pin configuration.
• The two bulb types are not interchangeable, as the wedge base of the 12961 and the end-cap contact design of the DE3423 represent physically incompatible socket formats.
• The transition between bulb types at the 2003-2004 model year boundary indicates a change in the license plate lamp socket design between those two generations of the XJ8.