BMW 650i Dome Light Bulb Size

The BMW 650i dome light requires bulb size 12961 or DE3423 depending on the specific version of the interior lighting component. Data for the bulb sizes covers the range from 2006 through 2010.

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
2008-2010	12961
2006-2007	DE3423

Bulb Specifications

Description	Bulb Size
Philips part number. Miniature wedge bulb (T10) with W2.1x9.5d base. 12V, 5W.	12961
ANSI standard (US & Canada). Festoon bulb, 41mm length, end-cap contacts. 12V.	DE3423

Other Locations

Additional Notes

The BMW 650i dome light uses two distinct bulb types across its model years, with the 12961 specified for 2008-2010 and the DE3423 specified for 2006-2007.
The 12961 is a Philips part number designating a T10 miniature wedge bulb with a W2.1x9.5d base, rated at 12V and 5W.
The T10 wedge form factor is named for its wedge-shaped base, which secures the bulb by friction rather than a twist or pin mechanism.
The W2.1x9.5d base designation describes the contact width and pin spacing of the wedge base, a standardized measurement used across many miniature automotive bulbs.
The DE3423 follows the ANSI standard used in the United States and Canada, designating a festoon-style bulb with a 41mm length and end-cap contacts, rated at 12V.
Festoon bulbs make electrical contact through metal caps at each end of the cylindrical body, a design that differs fundamentally from the wedge base of the 12961.
The two bulb types are not interchangeable, as the wedge base of the 12961 and the end-cap contact design of the DE3423 require physically different socket types.
No wattage is listed in the specifications for the DE3423, meaning its power draw cannot be directly compared to the 5W rating of the 12961 from the provided data alone.
Both bulb types operate on a 12V electrical system, consistent with standard automotive low-voltage architecture.
The shift from the DE3423 festoon type to the 12961 wedge type between the 2007 and 2008 BMW 650i indicates a socket change in the dome light housing across those model years.