BMW 525i Map Light Bulb Size

The BMW 525i map light uses 12961 and DE3423 bulb sizes for the interior lighting components. Available data for the specified vehicle covers the range from 1995 through 2007.

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
2004-2007	12961
2001-2003	DE3423 (Rear)
1995	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 525i map light specifications reference two distinct bulb types: the 12961 and the DE3423, each with a different physical format and contact design.
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 wedge base relies on the bulb's glass envelope being gripped directly by the socket contacts, with no separate metal base.
The DE3423 is an ANSI-standard festoon 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, which is a fundamentally different mounting method from a wedge base.
Because the 12961 and DE3423 use incompatible socket types, one is not a substitute for the other despite both operating at 12V.
The BMW 525i (2004-2007) uses the 12961 bulb for the map light position.
The 2001-2003 BMW 525i uses the DE3423 bulb specifically for the rear map light position.
The 1995 BMW 525i uses the DE3423 bulb without a positional qualifier, while the 2001-2003 model years carry an explicit rear designation for the same bulb type.
The DE3423 designation follows ANSI standardization, meaning it is a cross-manufacturer specification recognized across US and Canadian markets rather than a single-brand part number.