The Volvo S40 dome light requires a DE3423 bulb size for proper installation and function within the interior lighting system. Data for the specified component covers the range from 2000 to 2006.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Volvo S40 dome light uses the DE3423 bulb across the 2000-2006 model years.
The DE3423 is an ANSI-standardized festoon bulb, meaning it seats by pressing its end-cap contacts against spring clips rather than inserting into a socket.
Festoon bulbs are measured by their length, and the DE3423 has a 41mm body, which determines physical fit within the housing.
The DE3423 operates at 12 volts, consistent with standard automotive electrical systems.
The 2007-2008 Volvo S40 front dome light uses the 12961 bulb, a different type from the DE3423 used in earlier model years.
The 12961 is a Philips part number for a T10 miniature wedge bulb with a W2.1x9.5d base, which is a push-in wedge-style fitting incompatible with festoon-style spring-clip housings.
The 12961 is rated at 12 volts and 5 watts, placing it in the low-output range typical of interior courtesy lighting.
Because the DE3423 and 12961 use physically different base types, one cannot substitute for the other without a housing adapter or modification.