Jaguar XJ Dome Light Bulb Size

The Jaguar XJ dome light uses bulb size 6411 or DE3423 depending on the specific version of the vehicle. Available data covers the range from 1969 to 2017.

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
2010-2017	6411
1969-1971	DE3423

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Festoon bulb, 36mm length, SV8.5 base. 12V, 5W.	6411
ANSI standard (US & Canada). Festoon bulb, 41mm length, end-cap contacts. 12V.	DE3423

Other Locations

Additional Notes

The Jaguar XJ uses two distinct dome light bulb types across its model years: the 6411 and the DE3423, both classified as festoon bulbs under the ANSI standard applicable in the US and Canada.
Festoon bulbs are cylindrical lamps that make electrical contact at both ends of the housing rather than through a side-mounted base, a design common in interior automotive lighting applications.
The 6411 bulb is specified for the Jaguar XJ across the 2010-2017 model years, making it the more widely represented of the two bulb types in these specifications.
The 6411 operates at 12 volts with a 5-watt rating and uses an SV8.5 base, with a 36mm length.
The DE3423 is specified for the 1969-1971 Jaguar XJ and shares the festoon form factor but differs from the 6411 in both physical size and base type.
The DE3423 measures 41mm in length and uses end-cap contacts rather than the SV8.5 base found on the 6411, making the two bulbs physically incompatible with each other despite both being festoon types.
The 5mm difference in length between the 6411 and the DE3423 is a critical fitment factor, as festoon bulbs rely on a precise fit between the two contact points of the lamp holder.
No wattage rating is listed for the DE3423 in these specifications, whereas the 6411 is explicitly rated at 5W.
Both bulb types carry the same 12-volt operating voltage, consistent with the 12V electrical systems standard in passenger vehicles.
The differing base configurations of the 6411 (SV8.5) and the DE3423 (end-cap contacts) reflect an evolution in festoon bulb socket design across the decades separating the two sets of model years.